Human skin

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Human_skin

 

Human skin
Epidermis, dermis, and subcutis, showing a hair follicle, gland, and sebaceous gland

The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals' skin, and it is very similar to pig skin. Though nearly all human skin is covered with hair follicles, it can appear hairless. There are two general types of skin, hairy and glabrous skin (hairless). The adjective cutaneous literally means "of the skin" (from Latin cutis, skin).

Skin plays an important immunity role in protecting the body against pathogens and excessive water loss. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue. This is often discoloured and depigmented.

In humans, skin pigmentation (affected by melanin) varies among populations, and skin type can range from dry to non-dry and from oily to non-oily. Such skin variety provides a rich and diverse habitat for bacteria that number roughly 1000 species from 19 phyla, present on the human skin.

Structure

Human skin shares anatomical, physiological, biochemical and immunological properties with other mammalian lines, especially pig skin. Pig skin shares similar epidermal and dermal thickness ratios to human skin; pig and human skin share similar hair follicle and blood vessel patterns; biochemically the dermal collagen and elastic content is similar in pig and human skin; and pig skin and human skin have similar physical responses to various growth factors.

Skin has mesodermal cells, pigmentation, such as melanin provided by melanocytes, which absorb some of the potentially dangerous ultraviolet radiation (UV) in sunlight. It also contains DNA repair enzymes that help reverse UV damage, such that people lacking the genes for these enzymes have high rates of skin cancer. One form predominantly produced by UV light, malignant melanoma, is particularly invasive, causing it to spread quickly, and can often be deadly. Human skin pigmentation varies among populations in a striking manner. This has led to the classification of people(s) on the basis of skin colour.

In terms of surface area, the skin is the second largest organ in the human body (the inside of the small intestine is 15 to 20 times larger). For the average adult human, the skin has a surface area of from 1.5–2.0 square metres (16–22 sq ft). The thickness of the skin varies considerably over all parts of the body, and between men and women and the young and the old. An example is the skin on the forearm which is on average 1.3 mm in the male and 1.26 mm in the female. One average square inch (6.5 cm²) of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than 1,000 nerve endings. The average human skin cell is about 30 micrometres (μm) in diameter, but there are variants. A skin cell usually ranges from 25 to 40 μm², depending on a variety of factors.

Skin is composed of three primary layers: the epidermis, the dermis and the hypodermis.

Layers, Receptors, and Appendages of Human Skin

Epidermis

Main article: Epidermis

The epidermis, "epi" coming from the Greek meaning "over" or "upon", is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface which also serves as a barrier to infection and is made up of stratified squamous epithelium with an underlying basal lamina.

The epidermis contains no blood vessels, and cells in the deepest layers are nourished almost exclusively by diffused oxygen from the surrounding air and to a far lesser degree by blood capillaries extending to the outer layers of the dermis. The main type of cells that make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present. The epidermis can be further subdivided into the following strata (beginning with the outermost layer): corneum, lucidum (only in palms of hands and bottoms of feet), granulosum, spinosum, and basale. Cells are formed through mitosis at the basale layer. The daughter cells (see cell division) move up the strata changing shape and composition as they die due to isolation from their blood source. The cytoplasm is released and the protein keratin is inserted. They eventually reach the corneum and slough off (desquamation). This process is called "keratinization". This keratinized layer of skin is responsible for keeping water in the body and keeping other harmful chemicals and pathogens out, making skin a natural barrier to infection.

2D projection of a 3D OCT-tomogram of the skin at the fingertip, depicting the stratum corneum (~500 µm thick) with the stratum disjunctum on top and the stratum lucidum in the middle. At the bottom are the superficial parts of the dermis. The sweat ducts are clearly visible. (See also: Rotating 3D Version)

The epidermis contains no blood vessels and is nourished by diffusion from the dermis. The main type of cells that make up the epidermis are keratinocytes, melanocytes, Langerhans cells, and Merkel cells. The epidermis helps the skin regulate body temperature.

Layers

The skin has up to seven layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. The epidermis is divided into several layers, where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. After reaching the top layer stratum corneum they are eventually 'sloughed off', or desquamated. This process is called keratinization and takes place within weeks.

It was previously believed that the stratum corneum was "a simple, biologically inactive, outer epidermal layer comprising a fibrillar lattice of dead keratin". It is now understood that this is not true, and that the stratum corneum should be considered to be a live tissue. While it is true that the stratum corneum is mainly composed of terminally differentiated keratinocytes called corneocytes that are anucleated, these cells remain alive and metabolically functional until desquamated.

Sublayers

The epidermis is divided into the following 5 sublayers or strata:

• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale (also called "stratum germinativum")

Blood capillaries are found beneath the epidermis and are linked to an arteriole and a venule. Arterial shunt vessels may bypass the network in ears, the nose and fingertips.

Genes and proteins expressed in the epidermis

About 70% of all human protein-coding genes are expressed in the skin. Almost 500 genes have an elevated pattern of expression in the skin. There are fewer than 100 genes that are specific for the skin, and these are expressed in the epidermis. An analysis of the corresponding proteins show that these are mainly expressed in keratinocytes and have functions related to squamous differentiation and cornification.

Dermis

Main article: Dermis

The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbours many nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels. The blood vessels in the dermis provide nourishment and waste removal from its own cells as well as from the stratum basale of the epidermis.

The dermis is structurally divided into two areas: a superficial area adjacent to the epidermis, called the papillary region, and a deep thicker area known as the reticular region.

Papillary region

The papillary region is composed of loose areolar connective tissue. It is named for its finger-like projections called papillae, which extend toward the epidermis. The papillae provide the dermis with a "bumpy" surface that interdigitates with the epidermis, strengthening the connection between the two layers of skin.

In the palms, fingers, soles, and toes, the influence of the papillae projecting into the epidermis forms contours in the skin's surface. These epidermal ridges occur in patterns (see: fingerprint) that are genetically and epigenetically determined and are therefore unique to the individual, making it possible to use fingerprints or footprints as a means of identification.

Reticular region

The reticular region lies deep in the papillary region and is usually much thicker. It is composed of dense irregular connective tissue, and receives its name from the dense concentration of collagenous, elastic, and reticular fibres that weave throughout it. These protein fibres give the dermis its properties of strength, extensibility, and elasticity.

Also located within the reticular region are the roots of the hairs, sebaceous glands, sweat glands, receptors, nails, and blood vessels.

Tattoo ink is held in the dermis. Stretch marks, often from pregnancy and obesity, are also located in the dermis.

Subcutaneous tissue

The subcutaneous tissue (also hypodermis and subcutis) is not part of the skin, but lies below the dermis of the cutis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue, adipose tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (subcutaneous tissue contains 50% of body fat). Fat serves as padding and insulation for the body.

Cross-section

Skin layers, of both hairy and hairless skin

Development

Further information: Human embryogenesis § Integumentary system

Skin colour

Main article: Human skin colour

Human skin shows high skin colour variety from the darkest brown to the lightest pinkish-white hues. Human skin shows higher variation in colour than any other single mammalian species and is the result of natural selection. Skin pigmentation in humans evolved to primarily regulate the amount of ultraviolet radiation (UVR) penetrating the skin, controlling its biochemical effects.

The actual skin colour of different humans is affected by many substances, although the single most important substance determining human skin colour is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin colour of darker-skinned humans. The skin colour of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the haemoglobin circulating in the veins of the dermis. The red colour underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or the stimulation of the nervous system (anger, fear), arterioles dilate.

There are at least five different pigments that determine the colour of the skin. These pigments are present at different levels and places.

• Melanin: It is brown in colour and present in the basal layer of the epidermis.
• Melanoid: It resembles melanin but is present diffusely throughout the epidermis.
• Carotene: This pigment is yellow to orange in colour. It is present in the stratum corneum and fat cells of dermis and superficial fascia.
• Hemoglobin (also spelled haemoglobin): It is found in blood and is not a pigment of the skin but develops a purple colour.
• Oxyhemoglobin: It is also found in blood and is not a pigment of the skin. It develops a red colour.

There is a correlation between the geographic distribution of UV radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that highlight higher amounts of UVR reflect darker-skinned populations, generally located nearer towards the equator. Areas that are far from the tropics and closer to the poles have lower concentration of UVR, which is reflected in lighter-skinned populations.

In the same population it has been observed that adult human females are considerably lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation, and vitamin D which is synthesized from sunlight helps in absorbing calcium. For this reason it is thought that females may have evolved to have lighter skin in order to help their bodies absorb more calcium.

The Fitzpatrick scale is a numerical classification schema for human skin colour developed in 1975 as a way to classify the typical response of different types of skin to ultraviolet (UV) light:

I	Always burns, never tans	Pale, Fair, Freckles
II	Usually burns, sometimes tans	Fair
III	May burn, usually tans	Light Brown
IV	Rarely burns, always tans	Olive brown
V	Moderate constitutional pigmentation	Brown
VI	Marked constitutional pigmentation	Black

Ageing

Further information: senescence

Further information: Intrinsic and extrinsic ageing

A typical rash

Skin infected with scabies

As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages.

Among other things, skin ageing is noted by a decrease in volume and elasticity. There are many internal and external causes to skin ageing. For example, ageing skin receives less blood flow and lower glandular activity.

A validated comprehensive grading scale has categorized the clinical findings of skin ageing as laxity (sagging), rhytids (wrinkles), and the various facets of photoageing, including erythema (redness), and telangiectasia, dyspigmentation (brown discolouration), solar elastosis (yellowing), keratoses (abnormal growths) and poor texture.

Cortisol causes degradation of collagen, accelerating skin ageing.

Anti-ageing supplements are used to treat skin ageing.

Photoageing

Main article: Photoageing

Photoageing has two main concerns: an increased risk for skin cancer and the appearance of damaged skin. In younger skin, sun damage will heal faster since the cells in the epidermis have a faster turnover rate, while in the older population the skin becomes thinner and the epidermis turnover rate for cell repair is lower, which may result in the dermis layer being damaged.

UV-induced DNA damage

UV-irradiation of human skin cells generates damages in DNA through direct photochemical reactions at adjacent thymine or cytosine residues on the same strand of DNA. Cyclobutane pyrimidine dimers formed by two adjacent thymine bases, or by two adjacent cytosine bases, in DNA are the most frequent types of DNA damage induced by UV. Humans, as well as other organisms, are capable of repairing such UV-induced damages by the process of nucleotide excision repair. In humans this repair process protects against skin cancer.

Types

Though most human skin is covered with hair follicles, some parts can be hairless. There are two general types of skin, hairy and glabrous skin (hairless). The adjective cutaneous means "of the skin" (from Latin cutis, skin).

Functions

Skin performs the following functions:

1. Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defence; Langerhans cells in the skin are part of the adaptive immune system. Perspiration contains lysozyme that break the bonds within the cell walls of bacteria.
2. Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury; see somatosensory system and haptics.
3. Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss, while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
4. Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss. Loss of this function contributes to the massive fluid loss in burns.
5. Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness.
6. Storage and synthesis: acts as a storage centre for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.
7. Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.
8. Absorption: the cells comprising the outermost 0.25–0.40 mm of the skin are "almost exclusively supplied by external oxygen", although the "contribution to total respiration is negligible". In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.
9. Water resistance: The skin acts as a water-resistant barrier so essential nutrients are not washed out of the body.

Skin flora

Main article: Skin flora

The human skin is a rich environment for microbes. Around 1000 species of bacteria from 19 bacterial phyla have been found. Most come from only four phyla: Actinomycetota (51.8%), Bacillota (24.4%), Pseudomonadota (16.5%), and Bacteroidota (6.3%). Propionibacteria and Staphylococci species were the main species in sebaceous areas. There are three main ecological areas: moist, dry and sebaceous. In moist places on the body Corynebacteria together with Staphylococci dominate. In dry areas, there is a mixture of species but dominated by Betaproteobacteria and Flavobacteriales. Ecologically, sebaceous areas had greater species richness than moist and dry ones. The areas with least similarity between people in species were the spaces between fingers, the spaces between toes, axillae, and umbilical cord stump. Most similarly were beside the nostril, nares (inside the nostril), and on the back.

Reflecting upon the diversity of the human skin researchers on the human skin microbiome have observed: "hairy, moist underarms lie a short distance from smooth dry forearms, but these two niches are likely as ecologically dissimilar as rainforests are to deserts."

The NIH conducted the Human Microbiome Project to characterize the human microbiota which includes that on the skin and the role of this microbiome in health and disease.

Microorganisms like Staphylococcus epidermidis colonize the skin surface. The density of skin flora depends on region of the skin. The disinfected skin surface gets recolonized from bacteria residing in the deeper areas of the hair follicle, gut and urogenital openings.

Clinical significance

Further information: skin disease

Diseases of the skin include skin infections and skin neoplasms (including skin cancer). Dermatology is the branch of medicine that deals with conditions of the skin.

The skin is also valuable for diagnosis of other conditions, since many medical signs show through the skin. Skin color affects the visibility of these signs, a source of misdiagnosis in unaware medical personnel.

Society and culture

Hygiene and skin care

See also: Exfoliation (cosmetology)

The skin supports its own ecosystems of microorganisms, including yeasts and bacteria, which cannot be removed by any amount of cleaning. Estimates place the number of individual bacteria on the surface of 6.5 square centimetres (1 sq in) of human skin at 50 million, though this figure varies greatly over the average 1.9 square metres (20 sq ft) of human skin. Oily surfaces, such as the face, may contain over 78 million bacteria per square centimetre (500 million per square inch). Despite these vast quantities, all of the bacteria found on the skin's surface would fit into a volume the size of a pea. In general, the microorganisms keep one another in check and are part of a healthy skin. When the balance is disturbed, there may be an overgrowth and infection, such as when antibiotics kill microbes, resulting in an overgrowth of yeast. The skin is continuous with the inner epithelial lining of the body at the orifices, each of which supports its own complement of microbes.

Cosmetics should be used carefully on the skin because these may cause allergic reactions. Each season requires suitable clothing in order to facilitate the evaporation of the sweat. Sunlight, water and air play an important role in keeping the skin healthy.

Oily skin

Oily skin is caused by over-active sebaceous glands, that produce a substance called sebum, a naturally healthy skin lubricant. A high glycemic-index diet and dairy products (except for cheese) consumption increase IGF-1 generation, which in turn increases sebum production. Overwashing the skin does not cause sebum overproduction but may cause dryness.

When the skin produces excessive sebum, it becomes heavy and thick in texture, known as oily skin. Oily skin is typified by shininess, blemishes and pimples. The oily-skin type is not necessarily bad, since such skin is less prone to wrinkling, or other signs of ageing, because the oil helps to keep needed moisture locked into the epidermis (outermost layer of skin). The negative aspect of the oily-skin type is that oily complexions are especially susceptible to clogged pores, blackheads, and buildup of dead skin cells on the surface of the skin. Oily skin can be sallow and rough in texture and tends to have large, clearly visible pores everywhere, except around the eyes and neck.

Permeability

Human skin has a low permeability; that is, most foreign substances are unable to penetrate and diffuse through the skin. Skin's outermost layer, the stratum corneum, is an effective barrier to most inorganic nanosized particles. This protects the body from external particles such as toxins by not allowing them to come into contact with internal tissues. However, in some cases it is desirable to allow particles entry to the body through the skin. Potential medical applications of such particle transfer has prompted developments in nanomedicine and biology to increase skin permeability. One application of transcutaneous particle delivery could be to locate and treat cancer. Nanomedical researchers seek to target the epidermis and other layers of active cell division where nanoparticles can interact directly with cells that have lost their growth-control mechanisms (cancer cells). Such direct interaction could be used to more accurately diagnose properties of specific tumours or to treat them by delivering drugs with cellular specificity.

Nanoparticles

Nanoparticles 40 nm in diameter and smaller have been successful in penetrating the skin. Research confirms that nanoparticles larger than 40 nm do not penetrate the skin past the stratum corneum. Most particles that do penetrate will diffuse through skin cells, but some will travel down hair follicles and reach the dermis layer.

The permeability of skin relative to different shapes of nanoparticles has also been studied. Research has shown that spherical particles have a better ability to penetrate the skin compared to oblong (ellipsoidal) particles because spheres are symmetric in all three spatial dimensions. One study compared the two shapes and recorded data that showed spherical particles located deep in the epidermis and dermis whereas ellipsoidal particles were mainly found in the stratum corneum and epidermal layers. Nanorods are used in experiments because of their unique fluorescent properties but have shown mediocre penetration.

Nanoparticles of different materials have shown skin's permeability limitations. In many experiments, gold nanoparticles 40 nm in diameter or smaller are used and have shown to penetrate to the epidermis. Titanium oxide (TiO₂), zinc oxide (ZnO), and silver nanoparticles are ineffective in penetrating the skin past the stratum corneum. Cadmium selenide (CdSe) quantum dots have proven to penetrate very effectively when they have certain properties. Because CdSe is toxic to living organisms, the particle must be covered in a surface group. An experiment comparing the permeability of quantum dots coated in polyethylene glycol (PEG), PEG-amine, and carboxylic acid concluded the PEG and PEG-amine surface groups allowed for the greatest penetration of particles. The carboxylic acid coated particles did not penetrate past the stratum corneum.

Increasing permeability

Scientists previously believed that the skin was an effective barrier to inorganic particles. Damage from mechanical stressors was believed to be the only way to increase its permeability.

Recently, simpler and more effective methods for increasing skin permeability have been developed. Ultraviolet radiation (UVR) slightly damages the surface of skin and causes a time-dependent defect allowing easier penetration of nanoparticles. The UVR's high energy causes a restructuring of cells, weakening the boundary between the stratum corneum and the epidermal layer. The damage of the skin is typically measured by the transepidermal water loss (TEWL), though it may take 3–5 days for the TEWL to reach its peak value. When the TEWL reaches its highest value, the maximum density of nanoparticles is able to permeate the skin. While the effect of increased permeability after UVR exposure can lead to an increase in the number of particles that permeate the skin, the specific permeability of skin after UVR exposure relative to particles of different sizes and materials has not been determined.

There are other methods to increase nanoparticle penetration by skin damage: tape stripping is the process in which tape is applied to skin then lifted to remove the top layer of skin; skin abrasion is done by shaving the top 5–10 μm off the surface of the skin; chemical enhancement applies chemicals such as polyvinylpyrrolidone (PVP), dimethyl sulfoxide (DMSO), and oleic acid to the surface of the skin to increase permeability; electroporation increases skin permeability by the application of short pulses of electric fields. The pulses are high voltage and on the order of milliseconds when applied. Charged molecules penetrate the skin more frequently than neutral molecules after the skin has been exposed to electric field pulses. Results have shown molecules on the order of 100 μm to easily permeate electroporated skin.

Applications

A large area of interest in nanomedicine is the transdermal patch because of the possibility of a painless application of therapeutic agents with very few side effects. Transdermal patches have been limited to administer a small number of drugs, such as nicotine, because of the limitations in permeability of the skin. Development of techniques that increase skin permeability has led to more drugs that can be applied via transdermal patches and more options for patients.

Increasing the permeability of skin allows nanoparticles to penetrate and target cancer cells. Nanoparticles along with multi-modal imaging techniques have been used as a way to diagnose cancer non-invasively. Skin with high permeability allowed quantum dots with an antibody attached to the surface for active targeting to successfully penetrate and identify cancerous tumours in mice. Tumour targeting is beneficial because the particles can be excited using fluorescence microscopy and emit light energy and heat that will destroy cancer cells.

Sunblock and sunscreen

Sunblock and sunscreen are different important skin-care products though both offer full protection from the sun.

Sunblock—Sunblock is opaque and stronger than sunscreen, since it is able to block most of the UVA/UVB rays and radiation from the sun, and does not need to be reapplied several times in a day. Titanium dioxide and zinc oxide are two of the important ingredients in sunblock.

Sunscreen—Sunscreen is more transparent once applied to the skin and also has the ability to protect against UVA/UVB rays, although the sunscreen's ingredients have the ability to break down at a faster rate once exposed to sunlight, and some of the radiation is able to penetrate to the skin. In order for sunscreen to be more effective it is necessary to consistently reapply and use one with a higher sun protection factor.

Diet

Vitamin A, also known as retinoids, benefits the skin by normalizing keratinization, downregulating sebum production which contributes to acne, and reversing and treating photodamage, striae, and cellulite.

Vitamin D and analogues are used to downregulate the cutaneous immune system and epithelial proliferation while promoting differentiation.

Vitamin C is an antioxidant that regulates collagen synthesis, forms barrier lipids, regenerates vitamin E, and provides photoprotection.

Vitamin E is a membrane antioxidant that protects against oxidative damage and also provides protection against harmful UV rays. 

Several scientific studies confirmed that changes in baseline nutritional status affects skin condition. 

The Mayo Clinic lists foods they state help the skin: fruits and vegetables, whole-grains, dark leafy greens, nuts, and seeds.

16PF Questionnaire

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/16PF_Questionnaire

The Sixteen Personality Factor Questionnaire (16PF) is a self-report personality test developed over several decades of empirical research by Raymond B. Cattell, Maurice Tatsuoka and Herbert Eber. The 16PF provides a measure of personality and can also be used by psychologists, and other mental health professionals, as a clinical instrument to help diagnose psychiatric disorders, and help with prognosis and therapy planning. The 16PF can also provide information relevant to the clinical and counseling process, such as an individual's capacity for insight, self-esteem, cognitive style, internalization of standards, openness to change, capacity for empathy, level of interpersonal trust, quality of attachments, interpersonal needs, attitude toward authority, reaction toward dynamics of power, frustration tolerance, and coping style. Thus, the 16PF instrument provides clinicians with a normal-range measurement of anxiety, adjustment, emotional stability and behavioral problems. Clinicians can use 16PF results to identify effective strategies for establishing a working alliance, to develop a therapeutic plan, and to select effective therapeutic interventions or modes of treatment. It can also be used within other areas of psychology, such as career and occupational selection.

Beginning in the 1940s, Cattell used several techniques including the new statistical technique of common factor analysis applied to the English-language trait lexicon to elucidate the major underlying dimensions within the normal personality sphere. This method takes as its starting point the matrix of inter-correlations between these variables in an attempt to uncover the underlying source traits of human personality. Cattell found that personality structure was hierarchical, with both primary and secondary stratum level traits. At the primary level, the 16PF measures 16 primary trait constructs, with a version of the Big Five secondary traits at the secondary level. These higher-level factors emerged from factor-analyzing the 16 x 16 intercorrelation matrix for the sixteen primary factors themselves. The 16PF yields scores on primary and second-order "global" traits, thereby allowing a multilevel description of each individual's unique personality profile. A listing of these trait dimensions and their description can be found below. Cattell also found a third-stratum of personality organization that comprised just two overarching factors.

The measurement of normal personality trait constructs is an integral part of Cattell's comprehensive theory of intrapersonal psychological variables covering individual differences in cognitive abilities, normal personality traits, abnormal (psychopathological) personality traits, dynamic motivational traits, mood states, and transitory emotional states which are all taken into account in his behavioral specification/prediction equation. The 16PF has also been translated into over 30 languages and dialects and is widely used internationally.

Cattell and his co-workers also constructed downward extensions of the 16PF – parallel personality questionnaires designed to measure corresponding trait constructs in younger age ranges, such as the High School Personality Questionnaire (HSPQ) – now the Adolescent Personality Questionnaire (APQ) for ages 12 to 18 years, the Children's Personality Questionnaire (CPQ), the Early School Personality Questionnaire (ESPQ), as well as the Preschool Personality Questionnaire (PSPQ).

Cattell also constructed (T-data) tests of cognitive abilities such as the Comprehensive Ability Battery (CAB) – a multidimensional measure of 20 primary cognitive abilities, as well as measures of non-verbal visuo-spatial abilities, such as the three scales of the Culture-Fair Intelligence Test (CFIT). In addition, Cattell and his colleagues constructed objective (T-data) measures of dynamic motivational traits including the Motivation Analysis Test (MAT), the School Motivation Analysis Test (SMAT), as well as the Children's Motivation Analysis Test (CMAT). As for the mood state domain, Cattell and his colleagues constructed the Eight State Questionnaire (8SQ), a self-report (Q-data) measure of eight clinically important emotional/mood states, labeled Anxiety, Stress, Depression, Regression, Fatigue, Guilt, Extraversion, and Arousal.

Outline

The most recent edition of the Sixteen Personality Factor Questionnaire (16PF), released in 1993, is the fifth edition (16PF5e) of the original instrument. The self-report instrument was first published in 1949; the second and third editions were published in 1956 and 1962, respectively; and the five alternative forms of the fourth edition were released between 1967 and 1969.

The goal of the fifth edition revision in 1993 was to:

• update, improve, and simplify the language used in the test items;
• simplify the answer format;
• develop new validity scales;
• improve the psychometric properties of the test, including new reliability and validity data; and
• develop a new standardization sample (of 10,000 people) to reflect the current U.S. Census population.

The 16PF Fifth Edition contains 185 multiple-choice items which are written at a fifth-grade reading level. Of these items, 76% were from the four previous 16PF editions, although many of them were re-written to simplify or update the language. The item content typically sounds non-threatening and asks simple questions about daily behavior, interests, and opinions.

Item format

A characteristic of the 16PF items is that, rather than asking respondents to self-assess their personality as some instruments do (e.g., "I am a warm and friendly person; I am not a worrier; I am an even tempered person."), they tend instead to ask about daily, concrete situations, e.g.:

• When I find myself in a boring situation, I usually "tune out" and daydream about other things. True/False.
• When a bit of tact and convincing is needed to get people moving, I'm usually the one who does it. True/False.

Cattell argued that self-ratings relate to self-image, and are affected by self-awareness, and defensiveness about one's actual traits. The 16PF provides scores on 16 primary personality scales and five global personality scales, all of which are bi-polar (both ends of each scale have a distinct, meaningful definition). The instrument also includes three validity scales:

• a bi-polar Impression Management (IM) scale,
• an Acquiescence (ACQ) scale, and
• an Infrequency (INF) scale.

The Impression Management (IM) scale is a bipolar scale with high scores reflecting a preponderance of socially desirable responses and low scores reflecting a preponderance of socially undesirable responses. Possible reasons for an extremely high Impression Management score include: the examinee may actually behave in highly socially desirable ways, and responses are accurate self-descriptions; responses reflect an unconscious distortion consistent with the examinee's self-image but not with their behavior; or deliberate self-presentation as behaving in a highly socially desirable manner. A low impression management score suggests an unusual willingness to admit undesirable attributes or behaviors and can occur when an examinee is unusually self-critical, discouraged, or under stress.

The Acquiescence (ACQ) scale's purpose is to index the degree to which the examinee agreed with items regardless of what was being asked. A high score might indicate that the examinee misunderstood the item content, responded randomly, has an unclear self-image, or had a "yea-saying" response style.

The Infrequency (INF) scale comprises the most statistically infrequent responses on the test, which are all middle (b) responses and appear in the test booklet with a question mark. A score above the 95th percentile may indicate that the examinee had trouble reading or comprehending the questions, responded randomly, experienced consistent indecisiveness about the a or c response choice, or tried to avoid making the wrong impression by choosing the middle answer rather than one of the more definitive answers.

Administration

Administration of the test takes about 35–50 minutes for the paper-and-pencil version and about 30 minutes by computer. The test instructions are simple and straightforward and the test is un-timed; thus, the test is generally self-administrable and can be used in either an individual or a group setting. The 16PF test was designed for adults at least age 16 and older, but there are also parallel tests for various younger age ranges (e.g., the 16PF Adolescent Personality Questionnaire).

The 16PF Questionnaire has been translated into more than 30 languages and dialects. Thus the test can be administered in different languages, scored based on either local, national, or international normative samples, and computerized interpretive reports provided in about 23 different languages. The test has generally been culturally adapted (rather than just translated) in these countries, with local standardization samples plus reliability and validity information collected locally and presented in individual manuals.

Scoring

The test can be hand-scored using a set of scoring keys, or computer-scored by mailing-in or faxing-in the answer sheet to the publisher IPAT. There is also a software system that can be used to administer, score, and provide reports on the test results directly in the professional's office; and an Internet-based system that can also provide administration, scoring, and reports in a range of different languages.

After the test has been administered there is a total score computed from each of the 16 personality factors. These totals have been created in a way to correlate to the sten scale. Scores on the 16PF are presented on a 10-point scale, or standard-ten scale. The sten scale has a mean of 5.5 and a standard deviation of 2, with scores below 4 considered low and scores above 7 considered high. The sten scales are bipolar, meaning that each end of the scale has a distinct definition and meaning. Because bipolar scales are designated with "high" or "low" for each factor, a high score should not be considered to reflect a positive personality characteristic and a low score should not be considered to reflect a negative personality characteristic.

Interpretation

Cattell and Schuerger provided six steps that outline how they recommend interpreting the results of the 16PF:

1. Consider the context of the assessment.
2. Evaluate the Response Style Indexes by first checking responses on Factor B, and then looking at scores on the Infrequency, Impression Management, and Acquiescence scales.
3. Evaluate the Global Scale scores.
4. Evaluate the Primary Scales in the context of the Global Scales
5. Consider scale interactions
6. Integrate 16PF results in relation to the assessment question

There are about a dozen computer-generated interpretive reports that can be used to help interpret the test for different purposes, for example:

• Career Development Report
• Karson Clinical Report
• Cattell Comprehensive Personality Interpretation
• Teamwork Development Report,
• Management Potential Report,
• Security Selection Report
• Leadership Coaching Report

There are also many books that help with test interpretation, for example,

• 16PF Interpretation in Clinical Practice (Karson, Karson, & O'Dell, 1997),
• The 16PF: Personality in Depth (Cattell, H.B., 1989), and
• Essentials of the 16PF (Cattell, H.E. & Schuerger, J.M, 2003)

The 16PF traits are also included in the Psychological Evaluation Questionnaire (PEQ), which combines measures of both normal and abnormal personality traits into one test (Cattell, Cattell, Cattell, Russell, & Bedwell, 2003)

Raymond Cattell's 16 Personality Factors

Below is a table outlining the personality traits measured by the 16PF Questionnaire.

Descriptors of low range	Primary factor	Descriptors of high range
Impersonal, distant, cool, reserved, detached, formal, aloof	Warmth (A)	Warm, outgoing, attentive to others, kindly, easygoing, participating, likes people
Concrete-thinking, less intelligent, lower general mental capacity, unable to handle abstract problems	Reasoning (B)	Abstract-thinking, more intelligent, bright, higher general mental capacity, fast-learner
Reactive emotionally, changeable, affected by feelings, emotionally less stable, easily upset	Emotional Stability (C)	Emotionally stable, adaptive, mature, faces reality calmly
Deferential, cooperative, avoids conflict, submissive, humble, obedient, easily led, docile, accommodating	Dominance (E)	Dominant, forceful, assertive, aggressive, competitive, stubborn, bossy
Serious, restrained, prudent, taciturn, introspective, silent	Liveliness (F)	Lively, animated, spontaneous, enthusiastic, happy-go-lucky, cheerful, expressive, impulsive
Expedient, nonconforming, disregards rules, self-indulgent	Rule-Consciousness (G)	Rule-conscious, dutiful, conscientious, conforming, moralistic, staid, rule-bound
Shy, threat-sensitive, timid, hesitant, intimidated	Social Boldness (H)	Socially bold, venturesome, thick-skinned, uninhibited
Utilitarian, objective, unsentimental, tough-minded, self-reliant, no-nonsense, rough	Sensitivity (I)	Sensitive, aesthetic, sentimental, tender-minded, intuitive, refined
Trusting, unsuspecting, accepting, unconditional, easy	Vigilance (L)	Vigilant, suspicious, skeptical, distrustful, oppositional
Grounded, practical, prosaic, solution oriented, steady, conventional	Abstractedness (M)	Abstract, imaginative, absentminded, impractical, absorbed in ideas
Forthright, genuine, artless, open, guileless, naive, unpretentious, involved	Privateness (N)	Private, discreet, nondisclosing, shrewd, polished, worldly, astute, diplomatic
Self-assured, unworried, complacent, secure, free of guilt, confident, self-satisfied	Apprehension (O)	Apprehensive, self-doubting, worried, guilt-prone, insecure, worrying, self-blaming
Traditional, attached to familiar, conservative, respecting traditional ideas	Openness to Change (Q1)	Open to change, experimental, liberal, analytical, critical, freethinking, flexibility
Group-oriented, affiliative, a joiner and follower dependent	Self-Reliance (Q2)	Self-reliant, solitary, resourceful, individualistic, self-sufficient
Tolerates disorder, unexacting, flexible, undisciplined, lax, self-conflict, impulsive, careless of social rules, uncontrolled	Perfectionism (Q3)	Perfectionistic, organized, compulsive, self-disciplined, socially precise, exacting will power, control, self-sentimental
Relaxed, placid, tranquil, torpid, patient, composed low drive	Tension (Q4)	Tense, high-energy, impatient, driven, frustrated, over-wrought, time-driven
Primary Factors and Descriptors in Cattell's 16 Personality Factor Model (Adapted from Conn & Rieke, 1994).

Relationship to five-factor models

In the Fourth and Fifth Editions of the 16PF, there were five global factors that seem to correspond fairly closely to the "Big Five personality traits". The Big Five (BF) trait of Openness seems to be related to 16PF Openness/Tough-mindedness, The BF trait of Conscientiousness to the 16PF Self-Control, the BF Extraversion to the 16PF Extraversion, the BF Agreeableness/Dis-Agreeableness to the 16PF Independence/Accommodation, and the BF Neuroticism to the 16PF Anxiety. In fact, the development of the Big-Five factors began in 1963 with W.T. Norman factor-analyzing responses to the same items as the 16PF, replicating Cattell's work and suggested that five factors would be sufficient.

However, one big technical difference between Cattell's five Global Factors and popular five-factor models was Cattell's insistence on using oblique rotation in the factor analysis whereas Goldberg and Costa & McCrae used orthogonal rotation in their factor analysis. Oblique rotation allows the factors to correlate with each other, whereas orthogonal rotation restricts the factors from correlating with each other. Although personality traits are thought to be correlated, using orthogonal factor analysis makes the factors easier to understand and to work on statistically in research. This is one of the reasons the Big-Five traits have definitions that are different from the 16PF global factors. For example, as seen in the table below, in Cattell's model the primary personality trait of Dominance (Factor E) is strongly located in the Independence/Accommodation global factor which represents a quality of fearless, original thinking and forceful, independent actions. However, other popular big five models consider Dominance as a facet of several Big-Five traits, including Extraversion, Dis-Agreeableness, and Conscientiousness. Thus Dominance is spread across a range of Big-Five factors with little influence on any one (Cattell & Mead, 2008). Below is a table that shows how the 16 primary factors are related to the five global factors of the 16 Personality Factor theory. Compare with the Hierarchical Structure of the Big Five. Also, note that factor B is considered separate from the other factors because it is not a part of the hierarchical structure of personality in the same way as the other factors.

Factor analytic strategy

Assumptions shared by standardized personality tests, simply stated, are that humans possess characteristics or traits that are stable, vary from individual to individual, and can be measured. Factor analysis is a statistical procedure for reducing the redundancy in a set of intercorrelated scores. One major technique of factor analysis, the principal-components method, finds the minimum number of common factors that can account for an interrelated set of scores. Cattell's goal was to empirically determine and measure the essence of personality. Cattell used factor analysis to reduce thousands of psychological traits into what he believed to be 16 of the basic dimensions, or source traits of human personality. As a result, he created the 16PF personality test.

16PF global and primary factors

Introversion/Extroversion	Low Anxiety/High Anxiety	Receptivity/Tough-Mindedness	Accommodation/Independence	Lack of Restraint/Self-Control
A: Reserved/Warm	C: Emotionally Stable/Reactive	A: Warm/Reserved	E: Deferential/Dominant	F: Serious/Lively	B: Problem-Solving
F: Serious/Lively	L: Trusting/Vigilant	I: Sensitive/Unsentimental	H: Shy/Bold	G: Expedient/Rule-Conscious
H: Shy/Bold	O: Self-Assured/Apprehensive	M: Abstracted/Practical	L: Trusting/Vigilant	M: Abstracted/Practical
N: Private/Forthright	Q4: Relaxed/Tense	Q1: Open-to-Change/Traditional	Q1: Traditional/Open-to-Change	Q3: Tolerates Disorder/Perfectionistic
Q2: Self-Reliant/Group-Oriented

History and development

Cattell physical sciences background

The 16PF Questionnaire was created from a fairly unusual perspective among personality tests. Most personality tests are developed to measure just the pre-conceived traits that are of interest to a particular theorist or researcher. The main author of the 16PF, Raymond B. Cattell, had a strong background in the physical sciences, especially chemistry and physics, at a time when the basic elements of the physical world were being discovered, placed in the periodic table, and used as the basis for understanding the fundamental nature of the physical world and for further inquiry. From this background in the physical sciences, Cattell developed the belief that all fields are best understood by first seeking to find the fundamental underlying elements in that domain, and then developing a valid way to measure and research these elements (Cattell, 1965).

Personality research author Schuerger stated that:

Cattell's goal in creating the 16PF Questionnaire was to provide a thorough, research-based map of normal personality.

When Cattell moved from the physical sciences into the field of psychology in the 1920s, he described his disappointment about finding that it consisted largely of a wide array of abstract, unrelated theories and concepts that had little or no scientific bases. He found that most personality theories were based on philosophy and on personal conjecture, or were developed by medical professionals, such as Jean Charcot and Sigmund Freud, who relied on their personal intuition to reconstruct what they felt was going on inside people, based on observing individuals with serious psycho-pathological problems. Cattell (1957) described the concerns he felt as a scientist:

"In psychology there is an ocean of spawning intuitions and comfortable assumptions which we share with the layman, and out of which we climb with difficulty to the plateaus of scientific objectivity....Scientific advance hinges on the introduction of measurement to the field under investigation….Psychology has bypassed the necessary descriptive, taxonomic, and metric stages through which all healthy sciences first must pass….If Aristotle and other philosophers could get no further by sheer power of reasoning in two thousand years of observation, it is unlikely that we shall do so now.... For psychology to take its place as an effective science, we must become less concerned with grandiose theory than with establishing, through research, certain basic laws of relationship." (p.3-5)

Thus, Cattell's goal in creating the 16PF Questionnaire was to discover the number and nature of the fundamental traits of human personality and to develop a way to measure these dimensions. At the University of London, Cattell worked with Charles Spearman who was developing factor analysis to aid in his quest to discover the basic factors of human ability. Cattell thought that could also be applied to the area of personality. He reasoned that human personality must have basic, underlying, universal dimensions just as the physical world had basic building blocks (like oxygen and hydrogen). He felt that if the basic building blocks of personality were discovered and measured, then human behavior (e.g., creativity, leadership, altruism, or aggression) could become increasingly understandable and predictable.

Lexical Hypothesis (1936)

In 1936 Gordon Allport and H.S. Odbert hypothesized that:

Those individual differences that are most salient and socially relevant in people's lives will eventually become encoded into their language; the more important such a difference, the more likely is it to become expressed as a single word.

This statement has become known as the Lexical Hypothesis, which posits that if there is a word for a trait, it must be a real trait. Allport and Odbert used this hypothesis to identify personality traits by working through two of the most comprehensive dictionaries of the English language available at the time, and extracting 18,000 personality-describing words. From this gigantic list they extracted 4500 personality-describing adjectives which they considered to describe observable and relatively permanent traits.

Cattell and his colleagues began a comprehensive program of international research aimed at identifying and mapping out the basic underlying dimensions of personality. Their goal was to systematically measure the widest possible range of personality concepts, in a belief that "all aspects of human personality which are or have been of importance, interest, or utility have already become recorded in the substance of language" (Cattell, R. B., 1943, p. 483). They wanted to include every known personality dimension in their investigation, and thus began with the largest existing compilation of personality traits (Allport and Odbert, 1936). Over time, they used factor analysis to reduce the massive list of traits by analyzing the underlying patterns among them. They studied personality data from different sources (e.g. objective measures of daily behavior, interpersonal ratings, and questionnaire results), and measured these traits in diverse populations, including working adults, university students, and military personnel. (Cattell, 1957, 1973).

16 Personality Factors identified (1949)

The 16 Personality Factors were identified in 1949 by Raymond Cattell. He believed that in order to adequately map out personality, one had to utilize L-Data (life records or observation), Q data (information from questionnaires), and T-data (information from objective tests). The development of the 16PF Questionnaire, although confusingly named, was an attempt to develop an adequate measure of T-data.

Cattell analyzed the list of 4500 adjectives and organized the list of adjectives into fewer than 171 items and asked subjects to rate people whom they knew on each of the adjectives on the list (an example of L-data because the information was gathered from observers). This allowed Cattell to narrow down to 35 terms and factor analysis in 1945, 1947 and 1948 revealed a 11 or 12 factor solution.

In 1949 Cattell found that there were 4 additional factors, which he believed consisted of information that could only be provided through self-rating. This process allowed the use of ratings by observers, questionnaires, and objective measurements of actual behavior. In 1952 the ILLIAC I became available at the University of Illinois at Urbana-Champaign to be used for factor analysis.

Together the original 12 factors and the 4 covert factors made up the original 16 primary personality factors. As the five factor theory gained traction and research on the 16 factors continued, subsequent analysis identified five factors underlying the 16 factors. Cattell called these global factors.

The 16PF factorial structure resembles that of Szondi test and the Berufsbilder test (BTT), despite being based on different theories.

Analytic study and revisions of the factors (1949–2011)

Because the 16PF dimensions were developed through factor analysis, construct validity is provided by studies that confirm its factor structure. Over several decades of factor-analytic study, Cattell and his colleagues gradually refined and validated their list of underlying source traits. The search resulted in the sixteen unitary traits of the 16PF Questionnaire. These traits have remained the same over the last 50 years of research. In addition, the 16PF Questionnaire traits are part of a multi-variate personality model that provides a broader framework including developmental, environmental, and hereditary patterns of the traits and how they change across the life span (Cattell, 1973, 1979, 1980).

The validity of the factor structure of the 16PF Questionnaire (the 16 primary factors and 5 global factors) has been supported by more than 60 published studies (Cattell & Krug, 1986; Conn & Rieke, 1994; Hofer and Eber, 2002). Research has also supported the comprehensiveness of the 16PF traits: all dimensions on other major personality tests (e.g., the NEO Personality Inventory, the California Psychological Inventory, the Personality Research Form, and the Myers-Briggs Type Indicator) have been found to be contained within the 16PF scales in regression and factor-analytic studies (Conn & Rieke, 1994; Cattell, 1996).

Since its release in 1949, the 16PF Questionnaire has been revised four times: once in 1956, once in 1962, once in 1968, and the current version was developed in 1993. The US version of the test was also re-standardized in 2002, along with the development of forms for children and teenagers; versions for the UK, Ireland, France and the Netherlands were re-standardised in 2011. Additionally, there is a shortened form available primarily for employee selection and the questionnaire has been adapted into more than 35 languages. The questionnaire has also been validated in a range of international cultures over time.

The 16PF was distributed through the Institute for Personality and Ability Testing (IPAT), founded by Cattell and based in Savoy, Illinois. In January 2003, the Institute was purchased by UK private company, OPP Limited, who administered the 16PF worldwide. It later became a subsidiary of Performance Assessment Network (PAN) which in 2017 was acquired by PSI.

The original Big Five traits

From the beginning of his research, Cattell found personality traits to have a multi-level, hierarchical structure (Cattell, 1946). The first goal of these researchers was to find the most fundamental primary traits of personality. Next they factor-analyzed these numerous primary traits to see if these traits had a structure of their own—i.e. if some of them naturally went together in self-defining, meaningful groupings.

They consistently found that the primary traits themselves came together in particular, meaningful groupings to form broader secondary or global traits, each with its own particular focus and function within personality (Cattell & Schuerger, 2003). For example, the first global trait they found was Extraversion-Introversion. It resulted from the natural affinity of five primary traits that defined different reasons for an individual to move toward versus away from other people (see below). They found that there was a natural tendency for these traits to go together in the real world, and to define an important domain of human behavior—social behavior. This global factor Global Extraversion/Introversion (the tendency to move toward versus away from interaction with others) is composed from the following primary traits:

• Warmth (Factor A): the tendency to move toward others seeking closeness and connection because of genuine feelings of caring, sympathy, and concern (versus the tendency to be reserved and detached, and thus be independent and unemotional).
• Liveliness (Factor F): the tendency to be high-energy, fun-loving, and carefree, and to spontaneously move towards others in an animated, stimulating manner. Low-scorers tend to be more serious and self-restrained, and to be cautious, unrushed, and judicious.
• Social Boldness (Factor H): the tendency to seek social interaction in a confident, fearless manner, enjoying challenges, risks, and being the center of attention. Low-scorers tend to be shy and timid, and to be more modest and risk-avoidant.
• Forthrightness (Factor N): the tendency to want to be known by others—to be open, forthright, and genuine in social situations, and thus to be self-revealing and unguarded. Low-scorers tend to be more private and unself-revealing, and to be harder to get to know.
• Affiliative (Factor Q2): the tendency to seek companionship and enjoy belonging to and functioning in a group (inclusive, cooperative, good follower, willing to compromise). Low-scorers tend to be more individualistic and self-reliant and to value their autonomy.

In a similar manner, these researchers found that four other primary traits consistently merged to define another global factor which they called Receptivity or Openness (versus Tough-Mindedness). This factor was made up of four primary traits that describe different kinds of openness to the world:

• Openness to sensitive feelings, emotions, intuition, and aesthetic dimensions (Sensitivity – Factor I)
• Openness to abstract, theoretical ideas, conceptual thinking, and imagination (Abstractedness – Factor M)
• Openness to free thinking, inquiry, exploration of new approaches, and innovative solutions (Openness-to-Change – Factor Q1) and
• Openness to people and their feelings (Warmth – Factor A).

Another global factor, Self-Controlled (or conscientious) versus Unrestrained, resulted from the natural coming together of four primary factors that define the different ways that human beings manage to control their behavior:

• Rule-Consciousness (Factor G) involves adopting and conscientiously following society's accepted standards of behavior
• Perfectionism (Factor Q3) describes a tendency to be self-disciplined, organized, thorough, attentive to detail, and goal-oriented
• Seriousness (Factor F) involves a tendency to be cautious, reflective, self-restrained, and deliberate in making decisions; and
• Groundedness (Factor M) involves a tendency to stay focused on concrete, pragmatic, realistic solutions.

Because the global factors were developed by factor-analyzing the primary traits, the meanings of the global traits were determined by the primary traits which made them up. In addition, then the global factors provide the overarching, conceptual framework for understanding the meaning and function of each of the primary traits. Thus, the two levels of personality are essentially inter-connected and inter-related.

However it is the primary traits that provide a clear definition of the individual's unique personality. Two people might have exactly the same level of Extraversion, but still be quite different from each other. For example, they may both be at the 80% on Extraversion, and both tend to move toward others to the same degree, but they may be doing it for quite different reasons. One person might achieve an 80% on Extraversion by being high on Social Boldness (Factor H: confident, bold, talkative, adventurous, fearless attention-seeking) and on Liveliness (Factor F: high-energy, enthusiastic, fun-loving, impulsive), but Reserved (low on Factor A: detached, cool, unfeeling, objective). This individual would be talkative, bold, and impulsive but not very sensitive to others people's needs or feelings. The second Extravert might be high on Warmth (Factor A: kind, soft-hearted, caring and nurturing), and Group-Oriented (low Factor Q2: companionable, cooperative, and participating), but Shy (low on Factor H: timid, modest, and easily embarrassed). This second Extravert would tend to show quite different social behavior and be caring, considerate, and attentive to others but not forward, bold or loud—and thus have quite a different effect on his/her social environment.

Today, the global traits of personality are commonly known as the Big Five. The Big Five traits are most important for getting an abstract, theoretical understanding of the big, overarching domains of personality, and in understanding how different traits of personality relate to each other and how different research findings relate to each other. The big-five are important for understanding and interpreting an individual's personality profile mainly in getting a broad overview of their personality make-up at the highest level of personality organization. However, it is still the scores on the more specific primary traits that define the rich, unique personality make-up of any individual. These more-numerous primary traits have repeatedly been found to be the most powerful in predicting and understanding the complexity of actual daily behavior (Ashton, 1998; Goldberg, 1999; Mershon & Gorsuch, 1988; Paunonen & Ashton, 2001).

Key features

16PF is one of the world's most examined personality tests.

The 16PF assessment is easy to administer, requiring only 35 to 50 minutes to complete.

Five distinct report options give the 16PF test utility in a wide variety of settings.

Because the relationship between the test items and the traits measured by the 16PF instrument is not obvious, it is difficult for the test-taker to deliberately tailor responses to achieve a desired outcome.

The Couple's Counseling Report includes an easy-to-understand narrative summary of results to share with the couple.

Eternalism (philosophy of time)

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)

Illustration of the concept of eternalism, showing a man walking his dog. Time progresses through the series of snapshots from the bottom of the page to the top. In a common sense view of time, each of those four instants would exist one after another. According to eternalism, those four instants all equally exist.

In the philosophy of space and time, eternalism is an approach to the ontological nature of time, which takes the view that all existence in time is equally real, as opposed to presentism or the growing block universe theory of time, in which at least the future is not the same as any other time. Some forms of eternalism give time a similar ontology to that of space, as a dimension, with different times being as real as different places, and future events are "already there" in the same sense other places are already there, and that there is no objective flow of time.

It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.

The present

In classical philosophy, time is divided into three distinct regions: the "past", the "present", and the "future". Using that representational model, the past is generally seen as being immutably fixed, and the future as at least partly undefined. As time passes, the moment that was once the present becomes part of the past, and part of the future, in turn, becomes the new present. In this way time is said to pass, with a distinct present moment moving forward into the future and leaving the past behind. One view of this type, presentism, argues that only the present exists. The present does not travel forward through an environment of time, moving from a real point in the past and toward a real point in the future. Instead, is merely changes. The past and future do not exist and are only concepts used to describe the real, isolated, and changing present. This conventional model presents a number of difficult philosophical problems and may be difficult to reconcile with currently accepted scientific theories such as the theory of relativity.

The bar and ring paradox is an example of the relativity of simultaneity. Both ends of the bar pass through the ring simultaneously in the rest frame of the ring (left), but the ends of the bar pass one after the other in the rest frame of the bar (right).

It can be argued that special relativity eliminates the concept of absolute simultaneity and a universal present: according to the relativity of simultaneity, observers in different frames of reference can have different measurements of whether a given pair of events happened at the same time or at different times, with there being no physical basis for preferring one frame's judgments over another's. However, there are events that may be non-simultaneous in all frames of reference: when one event is within the light cone of another—its causal past or causal future—then observers in all frames of reference show that one event preceded the other. The causal past and causal future are consistent within all frames of reference, but any other time is "elsewhere", and within it there is no present, past, or future. There is no physical basis for a set of events that represents the present.

Many philosophers have argued that relativity implies eternalism. Philosopher of science Dean Rickles says that, "the consensus among philosophers seems to be that special and general relativity are incompatible with presentism." Christian Wüthrich argues that supporters of presentism can only salvage absolute simultaneity if they reject either empiricism or relativity. Dean Zimmerman and others argue for a single privileged frame whose judgments about length, time and simultaneity are the true ones, even if there is no empirical way to distinguish this frame.

The flow of time

Antiquity

Arguments for and against an independent flow of time have been raised since antiquity, represented by fatalism, reductionism, and Platonism: Classical fatalism argues that every proposition about the future exists, and it is either true or false, hence there is a set of every true proposition about the future, which means these propositions describe the future exactly as it is, and this future is true and unavoidable. Fatalism is challenged by positing that there are propositions that are neither true nor false, for example they may be indeterminate. Reductionism questions whether time can exist independently of the relation between events, and Platonism argues that time is absolute, and it exists independently of the events that occupy it.

Earlier, pre-Socratic Greek philosopher Parmenides of Elea had posited that existence is timeless and change is impossible (an idea popularized by his disciple Zeno of Elea and his paradoxes about motion).

Middle ages

The philosopher Katherin A. Rogers argued that Anselm of Canterbury took an eternalist view of time, although the philosopher Brian Leftow argued against this interpretation, suggesting that Anselm instead advocated a type of presentism. Rogers responded to this paper, defending her original interpretation. Rogers also discusses this issue in her book Anselm on Freedom, using the term "four-dimensionalism" rather than "eternalism" for the view that "the present moment is not ontologically privileged", and commenting that "Boethius and Augustine do sometimes sound rather four-dimensionalist, but Anselm is apparently the first consistently and explicitly to embrace the position." Taneli Kukkonen argues in the Oxford Handbook of Medieval Philosophy that "what Augustine's and Anselm's mix of eternalist and presentist, tenseless and tensed language tells is that medieval philosophers saw no need to choose sides" the way modern philosophers do.

Augustine of Hippo wrote that God is outside of time—that time exists only within the created universe. Thomas Aquinas took the same view, and many theologians agree. On this view, God would perceive something like a block universe, while time might appear differently to the finite beings contained within it.

Modern period

One of the most famous arguments about the nature of time in modern philosophy is presented in The Unreality of Time by J. M. E. McTaggart. It argues that time is an illusion. McTaggart argued that the description of events as existing in absolute time is self-contradictory, because the events have to have properties about being in the past and in the future, which are incompatible with each other. McTaggart viewed this as a contradiction in the concept of time itself, and concluded that reality is non-temporal. He called this concept the B-theory of time.

Dirck Vorenkamp, a professor of religious studies, argued in his paper "B-Series Temporal Order in Dogen's Theory of Time" that the Zen Buddhist teacher Dōgen presented views on time that contained all the main elements of McTaggart's B-series view of time (which denies any objective present), although he noted that some of Dōgen's reasoning also contained A-Series notions, which Vorenkamp argued may indicate some inconsistency in Dōgen's thinking.

A. Halliday has attempted to rationalise time by arguing that it is finite. This was founded on the thought that, if an entity has, or is assigned, parts then those parts must be finite. Assembling finite parts must result in a finite whole. Therefore, it follows that past, present and future are finite. It then follows that, as they also form a whole, then the whole of time is finite.

In the simplest case, if time is finite then it is limited. Time is thought of as existing inside of space. If there cannot be a gap between the edge of time and the limits of space, then time fills all of space, ensuring change everywhere. Therefore, time cannot flow if flow demands movement from one point to another?

Quantum physics

Some philosophers appeal to a specific theory that is "timeless" in a more radical sense than the rest of physics, the theory of quantum gravity. This theory is used, for instance, in Julian Barbour's theory of timelessness. On the other hand, George Ellis argues that time is absent in cosmological theories because of the details they leave out.

Recently, Hrvoje Nikolić has argued that a block time model solves the black hole information paradox.

Objections

Philosophers such as John Lucas argue that "The Block universe gives a deeply inadequate view of time. It fails to account for the passage of time, the pre-eminence of the present, the directedness of time and the difference between the future and the past." Similarly, Karl Popper argued in his discussion with Albert Einstein against determinism and eternalism from a common-sense standpoint.

A flow-of-time theory with a strictly deterministic future, which nonetheless does not exist in the same sense as the present, would not satisfy common-sense intuitions about time. Some have argued that common-sense flow-of-time theories can be compatible with eternalism, for example John G. Cramer’s transactional interpretation. Kastner (2010) "proposed that in order to preserve the elegance and economy of the interpretation, it may be necessary to consider offer and confirmation waves as propagating in a “higher space” of possibilities.

In Time Reborn, Lee Smolin argues that time is physically fundamental, in contrast to Einstein's view that time is an illusion. Smolin hypothesizes that the laws of physics are not fixed, but rather evolve over time via a form of cosmological natural selection. In The Singular Universe and the Reality of Time, co-authored with philosopher Roberto Mangabeira Unger, Smolin goes into more detail on his views on the physical passage of time. In contrast to the orthodox block universe view, Smolin argues that what instead exists is a "thick present" in which two events in the present can be causally related to each other. Marina Cortês and Lee Smolin also argue that certain classes of discrete dynamical systems demonstrate time asymmetry and irreversibility, which is inconsistent with the block universe interpretation of time.

Avshalom Elitzur vehemently rejects the block universe interpretation of time. At the Time in Cosmology conference, held at the Perimeter Institute for Theoretical Physics in 2016, Elitzur said: "I’m sick and tired of this block universe, ... I don’t think that next Thursday has the same footing as this Thursday. The future does not exist. It does not! Ontologically, it’s not there." Elitzur and Shahar Dolev argue that quantum mechanical experiments such as the Quantum Liar and the evaporation of black holes challenge the mainstream block universe model, and support the existence of an objective passage of time. Elitzur and Dolev believe that an objective passage of time and relativity can be reconciled, and that it would resolve many of the issues with the block universe and the conflict between relativity and quantum mechanics. Additionally, Elitzur and Dolev believe that certain quantum mechanical experiments provide evidence of apparently inconsistent histories, and that spacetime itself may therefore be subject to change affecting entire histories.

In popular culture

In fiction

Ideas related to Eternalism are described in Kurt Vonnegut’s novel, Slaughterhouse-Five. In the context of the novel, the Tralfamadorians are an alien species, members of which experience every point in time simultaneously. A character at one point argues that since all moments exist simultaneously, everyone is always alive-- a claim which implies Eternalism. The protagonist of the story, Billy Pilgrim, additionally lives his life out of sequence. It is stated that each moment of his life exists independent of the others, which is a clause of Eternalism.

Eternalism is also indirectly referenced in the comic book series Watchmen by Alan Moore. At one point, the character Dr. Manhattan describes how he perceives time in a manner which is consistent with Eternalism. He states that, from his perspective, the past, present, and future occur simultaneously. This is evidenced when he speaks about past or future events in the present tense, which is a frequent occurrence. His last line in the series is, "Nothing ends, Adrian. Nothing ever ends."

The science fiction novel The Number of the Beast , by Robert A. Heinlein, explores concepts related to Block Time. One protagonist, the mathematician Dr. Jacob Burroughs, invents a device which navigates through time as one scalar dimension in a six-dimensional universe. The novel unfolds across a variety of parallel worlds. Along with block time, it is implied that there exists a block plenum of innumerable alternate universes, with each being separated by one quantum step along an axis of space-time.

The game Warframe introduces eternalism in the story quest "The New War." The example provided in the game describes a situation in which a girl's parents are trapped in separate cells, but the girl can only save one of them, as the other parent will be killed in response. According to the rules of eternalism, as explained by one of the characters, there will be different versions of reality regarding which parent is saved. The reason provided is that though the girl is assigned to one future, the other is no less real.