Animal communication

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Great egret (Ardea alba) in a courtship display communicating the desire to find a mate

Animal communication is the transfer of information from one or a group of animals (sender or senders) to one or more other animals (receiver or receivers) that affects the current or future behavior of the receivers. Information may be sent intentionally, as in a courtship display, or unintentionally, as in the transfer of scent from predator to prey. Information may be transferred to an "audience" of several receivers. Animal communication is a rapidly growing area of study in disciplines including animal behavior, sociology, neurology and animal cognition. Many aspects of animal behavior, such as symbolic name use, emotional expression, learning and sexual behavior, are being understood in new ways.

When the information from the sender changes the behavior of a receiver, the information is referred to as a "signal". Signalling theory predicts that for a signal to be maintained in the population, both the sender and receiver should usually receive some benefit from the interaction. Signal production by senders and the perception and subsequent response of receivers are thought to coevolve.^[1] Signals often involve multiple mechanisms, e.g. both visual and auditory, and for a signal to be understood the coordinated behaviour of both sender and receiver require careful study.

Modes

A lamb investigates a rabbit, an example of interspecific communication using body posture and olfaction.

Visual

For information on the perception of visual signals, see Visual perception.

• Gestures: The best known form of communication involves the display of distinctive body parts, or distinctive bodily movements; often these occur in combination, so a movement acts to reveal or emphasize a body part. A notable example is the presentation of a parent herring gull’s bill to its chick as a signal for feeding. Like many gulls, the herring gull has a brightly coloured bill, yellow with a red spot on the lower mandible near the tip. When the parent returns to the nest with food, it stands over its chick and taps the bill on the ground; this elicits a begging response from a hungry chick (pecking at the red spot), which stimulates the parent to regurgitate food. The complete signal therefore involves a distinctive morphological feature (body part), the red-spotted bill, and a distinctive movement (tapping towards the ground) which makes the red spot highly visible to the chick. While all primates use some form of gesture,^[2] Frans de Waal concluded that apes and humans are unique in that only they use intentional gestures to communicate. He tested the hypothesis that gestures evolve into language by studying the gestures of bonobos and chimps.

A dog's visual tooth-baring threat display, accompanied by an auditory signal, growling

• Facial expression: Facial gestures play an important role in animal communication. Often a facial gesture is a signal of emotion. Dogs, for example, express anger through snarling and showing their teeth. In alarm their ears perk up, in fear the ears flatten while the dogs expose their teeth slightly and squint their eyes. Jeffrey Mogil studied the facial expressions of mice during increments of increasing pain; there were five recognizable facial expressions; orbital tightening, nose and cheek bulge, and changes in ear and whisker carriage.^[3]
• Gaze following: Social animals coordinate their communication by monitoring of each other's head and eye orientation. Such behaviour has long been recognized as an important component of communication during human development, and gaze-following has recently received much attention in animals. Studies have been conducted on apes, monkeys, dogs, birds, and tortoises, and have focused on two different tasks: "follow[ing] another’s gaze into distant space" and "follow[ing] another’s gaze geometrically around a visual barrier e.g. by repositioning themselves to follow a gaze cue when faced with a barrier blocking their view". The first ability has been found among a broad range of animals, while the second has been demonstrated only for apes, dogs, wolves, and corvids (ravens); attempts to demonstrate this "geometric gaze following" in marmoset and ibis gave negative results. Researchers do not yet have a clear picture of the cognitive basis of gaze following, but developmental evidence indicates that "simple" gaze following and "geometric" gaze following probably rely on different cognitive mechanisms.^[4]
• Color change: Color change can be separated into changes that occur during growth and development, and those triggered by mood, social context, or abiotic factors such as temperature. The latter are seen in many taxa. Some cephalopods, such as the octopus and the cuttlefish, have specialized skin cells (chromatophores) that can change the apparent colour, opacity, and reflectiveness of their skin.^[5] In addition to their use for camouflage, rapid changes in skin color are used while hunting and in courtship rituals.^[6] Cuttlefish may display two entirely different signals simultaneously from opposite sides of their body. When a male cuttlefish courts a female in the presence of other males, he displays a male pattern facing the female and a female pattern facing away, to deceive other males.^[7] Some color signals occur in cycles. For example, when a female olive baboon begins to ovulate, her anogenital area swells and turns a bright red/pink. This signals to males that she is ready to mate.^[8]
• Bioluminescent communication: Communication by the production of light occurs commonly in vertebrates and invertebrates in the oceans, particularly at depths (e.g. angler fish). Two well known forms of land bioluminescence occur in fireflies and glow worms. Other insects, insect larvae, annelids, arachnids and even species of fungi possess bioluminescent abilities. Some bioluminescent animals produce the light themselves whereas others have a symbiotic relationship with bioluminescent bacteria. (See also: List of bioluminescent organisms)

Auditory

Bird calls can serve as alarms or keep members of a flock in contact, while the longer and more complex bird songs are associated with courtship and mating.^[9]

Many animals communicate through vocalization. Vocal communication serves many purposes, including mating rituals, warning calls, conveying location of food sources, and social learning. In a number of species, males perform calls during mating rituals as a form of competition against other males and to signal females. Examples include frogs, hammer-headed bats, red deer, humpback whales, elephant seals, and songbirds.^[10] Other instances of vocal communication include the alarm calls of the Campbell monkey,^[11] the territorial calls of gibbons, and the use of frequency in greater spear-nosed bats to distinguish between groups.^[12] The vervet monkey gives a distinct alarm call for each of its four different predators, and the reactions of other monkeys vary appropriately according to the call. For example, if an alarm call signals a python, the monkeys climb into the trees, whereas the "eagle" alarm causes monkeys to seek a hiding place on the ground. Prairie dogs also use complex calls that signal predator differences. According to Con Slobodchikoff and others, prairie dog calls communicate the type, size, and speed of an approaching predator.^{[13][14][15][16]} Whale vocalizations have been found to have different dialects based on region.^[17]

Not all animals use vocalization as a means of auditory communication. Many arthropods rub specialized body parts together to produce sound. This is known as stridulation. Crickets and grasshoppers are well known for this, but many others use stridulation as well, including crustaceans, spiders, scorpions, wasps, ants, beetles, butterflies, moths, millipedes, and centipedes. Another means of auditory communication is the vibration of swim bladders in bony fish. The structure of swim bladders and the attached sonic muscles varies greatly across bony fish families, resulting in a wide variety of sounds. Striking body parts together can also produce auditory signals. A well-known example of this is the tail tip vibration of rattlesnakes as a warning signal. Other examples include bill clacking in birds, wing clapping in manakin courtship displays, and chest beating in gorillas.^[18]

Olfactory

Despite being the oldest method of communication, chemical communication is one of the least understood forms due in part to the sheer abundance of chemicals in our environment and the difficulty of detecting and measuring all the chemicals in a sample.^[18] The ability to detect chemicals in the environment serves many functions, a crucial one being the detection of food, a function that first arose in single-celled organisms (bacteria) living in the oceans during the early days of life on Earth.^[18] As this function evolved, organisms began to differentiate between chemicals compounds emanating from resources, conspecifics (same species; i.e., mates and kin), and heterospecifics (different species; i.e., competitors and predators).^[18] For instance, a small minnow species may do well to avoid habitat with a detectable concentration of chemical cue associated with a predator species such as northern pike.^[19] Minnows with the ability to perceive the presence of predators before they are close enough to be seen and then respond with adaptive behaviour (such as hiding) are more likely to survive and reproduce.^{[citation needed]} Scent marking and scent rubbing are common forms of olfactory communication in mammals.^[20][21]

Electric

Electrocommunication is a rare form of communication in animals. It is seen primarily in aquatic animals, though some land mammals, notably the platypus and echidnas, sense electric fields that might be used for communication.^[22]

Weakly electric fishes provide an example of electrocommunication, together with electrolocation. These fish use an electric organ to generate an electric field, which is detected by electroreceptors. Differences in the waveform and frequency of changes in the field convey information on species, sex, and identity. These electric signals can be generated in response to hormones, circadian rhythms, and interactions with other fish. Some predators, such as sharks and rays, are able to eavesdrop on these electrogenic fish through passive electroreception.

Touch

Touch is a key factor in many social interactions. Here are some examples:

• Fighting: In a fight, touch may be used to challenge an opponent and to coordinate movements during the fight. It may also be used by the loser to indicate submission.
• Mating: Mammals often initiate mating by grooming, stroking or rubbing against each other. This provides the opportunity to apply chemical signals and to assess those excreted by the potential mate. Touch may also announce the intention of the male to mount the female, as when a male kangaroo grabs the tail of a female. During mating, touch stimuli are important for pair positioning, coordination and genital stimulation.
• Social integration: Touch is widely used for social integration, a use that is typified by the social grooming of one animal by another. Social grooming has several functions; it removes parasites and debris from the groomed animal, it reaffirms the social bond or hierarchical relationship between the animals, and it gives the groomer an opportunity to examine olfactory cues on the groomed individual, perhaps adding additional ones. This behaviour has been observed in social insects, birds and mammals.
• Foraging: Some ant species recruit fellow workers to new food finds by first tapping them with their antennae and forelegs, then leading them to the food source while keeping physical contact. Another example of this is the waggle dance of honey bees.^[23]
• Huddling: Prolonged physical contact or huddling also serves social integration. Huddling promotes heat exchange, together with the transfer of olfactory or tactile information. Some organisms live in constant contact in a colony, for example colonial corals. When individuals are linked tightly in this way an entire colony can react on the aversive or alarm movements made by only a few individuals. In several herbivorous insect nymphs and larvae, aggregations where there is prolonged contact play a major role in group coordination. These aggregations may take the form of a procession or a rosette.

Seismic

Seismic communication is the exchange of information using self-generated vibrational signals transmitted via a substrate such as the soil, water, spider webs, plant stems, or a blade of grass. This form of communication has several advantages, for example it can be sent regardless of light and noise levels, and it usually has a short range and short persistence, which may reduce the danger of detection by predators. The use of seismic communication is found in many taxa, including frogs, kangaroo rats, mole rats, bees, nematode worms, and others. Tetrapods usually make seismic waves by drumming on the ground with a body part, a signal that is sensed by the sacculus of the receiver. The sacculus is an organ in the inner ear containing a membranous sac that is used for balance, but can also detect seismic waves in animals that use this form of communication. Vibrations may be combined with other sorts of communication.^[24]

Thermal

A python (top) and rattlesnake illustrating the positions of the pit organs. Red arrows indicate the pit organs whereas black arrows indicate the nostril.

A number of different snakes have the ability to sense infrared (IR) thermal radiation, which allows these reptiles to derive thermal images from the radiant heat emitted by predators or prey at wavelengths between 5 and 30 μm. The accuracy of this sense is such that a blind rattlesnake can target its strike to the vulnerable body parts of a prey animal.^[25] It was previously thought that the pit organs evolved primarily as prey detectors, but it is now believed that they may also be used to control body temperature.^[26]

The facial pits enabling thermoregulation underwent parallel evolution in pitvipers and some boas and pythons, having evolved once in pitvipers and multiple times in boas and pythons.^[27] The electrophysiology of the structure is similar between lineages, but it differs in gross structure anatomy. Most superficially, pitvipers possess one large pit organ on either side of the head, between the eye and the nostril (loreal pit), while boas and pythons have three or more comparatively smaller pits lining the upper and sometimes the lower lip, in or between the scales. Those of the pitvipers are the more advanced, having a suspended sensory membrane as opposed to a simple pit structure.
ithin the family Viperidae, the pit organ is seen only in the subfamily Crotalinae: the pitvipers. Despite the detection of IR radiation, the pits’ IR mechanism is dissimilar to photoreceptors; while photoreceptors detect light via photochemical reactions, the protein in the facial pits of snakes is a temperature sensitive ion channel. It senses infrared signals through a mechanism involving warming of the pit organ, rather than chemical reaction to light.^[28] This is consistent with the thin pit membrane, which allows incoming IR radiation to quickly and precisely warm a given ion channel and trigger a nerve impulse, as well as vascularize the pit membrane to rapidly cool the ion channel back to its original “resting” or “inactive” temperature.^[28]

Common vampire bats (Desmodus rotundus) have specialized IR sensors in their nose-leaf.^[29] Vampire bats are the only mammals that feed exclusively on blood. The IR sense enables Desmodus to localize homeothermic animals such as cattle and horses within a range of about 10 to 15 cm. This infrared perception may be used in detecting regions of maximal blood flow on targeted prey.

Autocommunication

Autocommunication is a type of communication in which the sender and receiver are the same individual. The sender emits a signal that is altered by the environment and eventually is received by the same individual. The altered signal provides information that can indicate food, predators or conspecifics. Because the sender and receiver are the same animal, selection pressure maximizes signal efficacy, i.e. the degree to which an emitted signal is correctly identified by a receiver despite propagation distortion and noise. There are two types of autocommunication. The first is active electrolocation found in the electric fish Gymnotiformes (knifefishes) and Mormyridae (elephantfish) and also in the platypus (Ornithorhynchus anatinus). The second type of autocommunication is echolocation, found in bats and toothed whales.

Functions

There are many functions of animal communication. However, some have been studied in more detail than others. This includes:

• Communication during contests: Animal communication plays a vital role in determining the winner of contest over a resource. Many species have distinct signals that signal aggression or willingness to attack or signals to convey retreat during competitions over food, territories, or mates.
• Mating rituals: Animals produce signals to attract the attention of a possible mate or to solidify pair bonds. These signals frequently involve the display of body parts or postures. For example, a gazelle will assume characteristic poses to initiate mating. Mating signals can also include the use of olfactory signals or mating calls unique to a species. Animals that form lasting pair bonds often have symmetrical displays that they make to each other. Famous examples are the mutual presentation of reeds by great crested grebes studied by Julian Huxley, the triumph displays shown by many species of geese and penguins on their nest sites, and the spectacular courtship displays by birds of paradise.
• Ownership/territorial: Signals used to claim or defend a territory, food, or a mate.
• Food-related signals: Many animals make "food calls" to attract a mate, offspring, or other members of a social group to a food source. Perhaps the most elaborate food-related signal is the Waggle dance of honeybees studied by Karl von Frisch. One well-known example of begging of offspring in a clutch or litter is altricial songbirds. Young ravens signal will signal to older ravens when they encounter new or untested food. Rhesus macaques will send food calls to inform other monkeys of a food source to avoid punishment. Pheromones are released by many social insects to lead the other members of the society to the food source. For example, ants leave a pheromone trail on the ground that can be followed by other ants to lead them to the food source.
• Alarm calls: Alarm calls communicate the threat of a predator. This allows all members of a social group (and sometimes other species) to respond accordingly. This may include running for cover, becoming immobile, or gathering into a group to reduce the risk of attack. Alarm signals are not always vocalizations. Crushed ants will release an alarm pheromone to attract more ants and send them into an attack state.
• Meta-communication: Signals that will modify the meaning of subsequent signals. One example is the 'play face' in dogs which signals that a subsequent aggressive signal is part of a play fight rather than a serious aggressive episode.

Interpretation of animal behaviour

As described above, many animal gestures, postures, and sounds, convey meaning to nearby animals. These signals are often easier to describe than to interpret. It is tempting, especially with domesticated animals and apes, to anthropomorphize, that is, to interpret animal actions in human terms, but this can be quite misleading; for example, an ape's "smile" is often a sign of aggression. Also, the same gesture may have different meanings depending on context within which it occurs. For example, a domestic dog's tail wag and posture may be used in different ways to convey many meanings as illustrated in Charles Darwin's The Expression of the Emotions in Man and Animals published in 1872. Some of Darwin's illustrations are reproduced here.

• Examples of tail position indicating different emotions in dogs
• 

  "Small dog watching a cat on a table"
• 

  "Dog approaching another dog with hostile intentions"
• 

  "Dog in a humble and affectionate frame of mind"
• 

  "Half-bred shepherd dog"
• 

  "Dog caressing his master"

Interspecific communication

Much animal communication is intraspecific, that is, it occurs between members of the same species. As for interspecific communication, that between predator and prey is of particular interest.

Prey to predator

If a prey animal moves, makes a noise or vibrations, or emits a smell in such a way that a predator can detect it, this is consistent with the definition of "communication" given above. This type of communication is known as interceptive eavesdropping if a predator intercepts a message intended for conspecifics.

There are however, some actions of prey species are clearly directed to actual or potential predators. A good example is warning coloration: species such as wasps that are capable of harming potential predators are often brightly coloured, and this modifies the behaviour of the predator, who either instinctively or as the result of experience will avoid attacking such an animal. Some forms of mimicry fall in the same category: for example hoverflies are coloured in the same way as wasps, and although they are unable to sting, the strong avoidance of wasps by predators gives the hoverfly some protection. There are also behavioural changes that act in a similar way to warning colouration. For example, canines such as wolves and coyotes may adopt an aggressive posture, such as growling with their teeth bared, to indicate they will fight if necessary, and rattlesnakes use their well-known rattle to warn potential predators of their venomous bite. Sometimes, a behavioural change and warning colouration will be combined, as in certain species of amphibians which have most of their body coloured to blend with their surroundings, except for a brightly coloured belly. When confronted with a potential threat, they show their belly, indicating that they are poisonous in some way.

Another example of prey to predator communication is the pursuit-deterrent signal. Pursuit-deterrent signals occur when prey indicates to a predator that pursuit would be unprofitable because the signaler is prepared to escape. Pursuit-deterrent signals provide a benefit to both the signaler and receiver; they prevent the sender from wasting time and energy fleeing, and they prevent the receiver from investing in a costly pursuit that is unlikely to result in capture. Such signals can advertise prey’s ability to escape, and reflect phenotypic condition (quality advertisement), or can advertise that the prey has detected the predator (perception advertisement). Pursuit-deterrent signals have been reported for a wide variety of taxa, including fish (Godin and Davis, 1995), lizards (Cooper et al., 2004), ungulates (Caro, 1995), rabbits (Holley 1993), primates (Zuberbuhler et al. 1997), rodents (Shelley and Blumstein 2005, Clark, 2005), and birds (Alvarez, 1993, Murphy, 2006, 2007). A familiar example of quality advertisement pursuit-deterrent signal is stotting (sometimes called pronking), a pronounced combination of stiff-legged running while simultaneously jumping shown by some antelopes such as Thomson's gazelle in the presence of a predator. At least 11 hypotheses for stotting have been proposed. A leading theory today is that it alerts predators that the element of surprise has been lost. Predators like cheetahs rely on surprise attacks, proven by the fact that chases are rarely successful when antelope stot. Predators do not waste energy on a chase that will likely be unsuccessful (optimal foraging behaviour). Quality advertisement can be communicated by modes other than visual. The banner-tailed kangaroo rat produces several complex foot-drumming patterns in a number of different contexts, one of which is when it encounters a snake. The foot-drumming may alert nearby offspring but most likely conveys vibrations through the ground that the rat is too alert for a successful attack, thus preventing the snake's predatory pursuit.^[30]

Predator to prey

The humpback anglerfish angles for small fish by deceptively dangling a bioluminescent lure in front of its jaws.

Typically, predators attempt to reduce communication to prey as this will generally reduce the effectiveness of their hunting. However, some forms of predator to prey communication occur in ways that change the behaviour of the prey and make their capture easier, i.e. deception by the predator. A well-known example is the angler fish, an ambush predator which waits for its prey to come to it. It has a fleshy bioluminescent growth protruding from its forehead which it dangles in front of its jaws. Smaller fish attempt to take the lure, placing themselves in a better position for the angler fish to catch them. Another example of deceptive communication is observed in the genus of jumping spiders (Myrmarachne). These spiders are commonly referred to as “antmimicking spiders” because of the way they wave their front legs in the air to simulate antennae.

Human/animal

Various ways in which humans interpret the behaviour of animals, or give commands to them, are consistent with the definition of interspecies communication. Skillful interpretation of animal communications may be critical to the welfare of animals that are being cared for or trained by humans. For example, behaviours indicating pain need to be recognized. Indeed, the survival of both the animal and its human caretaker may be at stake if, for example, a human fails to recognize a signal for imminent attack

Since the late 1990s, one scientist, Sean Senechal, has been developing, studying, and using the learned visible, expressive language in dogs and horses. By teaching these animals a gestural (human made) American Sign Language-like language, the animals have been found to use the new signs on their own to get what they need.^[31] The recent experiments on animal language are perhaps the most sophisticated attempt yet to establish human/animal communication, though their relation to natural animal communication is uncertain.

Other aspects

Evolution

The importance of communication is evident from the highly elaborate morphology, behaviour and physiology that some animals have evolved to facilitate this. These include some of the most striking structures in the animal kingdom, such as the peacock's tail, the antlers of a stag and the frill of the frill-necked lizard, but also include even the modest red spot on a European herring gull's bill. Highly elaborate behaviours have evolved for communication such as the dancing of cranes, the pattern changes of cuttlefish, and the gathering and arranging of materials by bowerbirds. Other evidence for the importance of communication in animals is the prioritisation of physiological features to this function, for example, birdsong appears to have brain structures entirely devoted to its production. All these adaptations require evolutionary explanation.

There are two aspects to the required explanation:

• identifying a route by which an animal that lacked the relevant feature or behaviour could acquire it;
• identifying the selective pressure that makes it adaptive for animals to develop structures that facilitate communication, emit communications, and respond to them.

Significant contributions to the first of these problems were made by Konrad Lorenz and other early ethologists. By comparing related species within groups, they showed that movements and body parts that in the primitive forms had no communicative function could be "captured" in a context where communication would be functional for one or both partners, and could evolve into a more elaborate, specialised form. For example, Desmond Morris showed in a study of grass finches^{[citation needed]} that a beak-wiping response occurred in a range of species, serving a preening function, but that in some species this had been elaborated into a courtship signal.

The second problem has been more controversial. The early ethologists assumed that communication occurred for the good of the species as a whole, but this would require a process of group selection which is believed to be mathematically impossible in the evolution of sexually reproducing animals. Altruism towards an unrelated group is not widely accepted in the scientific community, but rather can be seen as reciprocal altruism, expecting the same behaviour from others, a benefit of living in a group. Sociobiologists argued that behaviours that benefited a whole group of animals might emerge as a result of selection pressures acting solely on the individual. A gene-centered view of evolution proposes that behaviours that enabled a gene to become wider established within a population would become positively selected for, even if their effect on individuals or the species as a whole was detrimental;^[32]

The apparently excessive eye-spot signalling by the male peacock tail may be runaway selection

In the case of communication, an important discussion by John Krebs and Richard Dawkins established hypotheses for the evolution of such apparently altruistic or mutualistic communications as alarm calls and courtship signals to emerge under individual selection. This led to the realization that communication might not always be "honest" (indeed, there are some obvious examples where it is not, as in mimicry). The possibility of evolutionarily stable dishonest communication has been the subject of much controversy, with Amotz Zahavi in particular arguing that it cannot exist in the long term. Sociobiologists have also been concerned with the evolution of apparently excessive signaling structures such as the peacock's tail; it is widely thought that these can only emerge as a result of sexual selection, which can create a positive feedback process that leads to the rapid exaggeration of a characteristic that confers an advantage in a competitive mate-selection situation.

One theory to explain the evolution of traits like a peacock's tail is 'runaway selection'. This requires two traits—a trait that exists, like the bright tail, and a prexisting bias in the female to select for that trait. Females prefer the more elaborate tails, and thus those males are able to mate successfully. Exploiting the psychology of the female, a positive feedback loop is enacted and the tail becomes bigger and brighter. Eventually, the evolution will level off because the survival costs to the male do not allow for the trait to be elaborated any further. Two theories exist to explain runaway selection. The first is the good genes hypothesis. This theory states that an elaborate display is an honest signal of fitness and truly is a better mate. The second is the handicap hypothesis. This explains that the peacock's tail is a handicap, requiring energy to keep and makes it more visible to predators. Thus, the signal is costly to maintain, and remains an honest indicator of the signaler's condition. Another assumption is that the signal is more costly for low quality males to produce than for higher quality males to produce. This is simply because the higher quality males have more energy reserves available to allocate to costly signaling.^[1]

Cognitive aspects

Ethologists and sociobiologists have characteristically analysed animal communication in terms of more or less automatic responses to stimuli, without raising the question of whether the animals concerned understand the meaning of the signals they emit and receive. That is a key question in animal cognition. There are some signalling systems that seem to demand a more advanced understanding. A much discussed example is the use of alarm calls by vervet monkeys. Robert Seyfarth and Dorothy Cheney showed that these animals emit different alarm calls in the presence of different predators (leopards, eagles, and snakes), and the monkeys that hear the calls respond appropriately—but that this ability develops over time, and also takes into account the experience of the individual emitting the call. Metacommunication, discussed above, also seems to require a more sophisticated cognitive process.

It has been reported ^[33] that bottlenose dolphins can recognize identity information from whistles even when otherwise stripped of the characteristics of the whistle; making dolphins the only animals other than humans that have been shown to transmit identity information independent of the caller’s voice or location. The paper concludes that:

The fact that signature whistle shape carries identity information independent from voice features presents the possibility to use these whistles as referential signals, either addressing individuals or referring to them, similar to the use of names in humans. Given the cognitive abilities of bottlenose dolphins, their vocal learning and copying skills, and their fission–fusion social structure, this possibility is an intriguing one that demands further investigation.

— V. M. Janik, et al. ^[33]

Human behaviour

Another controversial issue is the extent to which human behaviours resemble animal communication, or whether all such communication has disappeared as a result of our linguistic capacity. Some of our bodily features—eyebrows, beards and moustaches, deep adult male voices, perhaps female breasts—strongly resemble adaptations to producing signals. Ethologists such as Irenäus Eibl-Eibesfeldt have argued that facial gestures such as smiling, grimacing, and the eyebrow flash on greeting are universal human communicative signals that can be related to corresponding signals in other primates. Given how recently spoken language has emerged, it is very likely that human body language does include some more or less involuntary responses that have a similar origin to the communication we have.

Humans also often seek to mimic animals' communicative signals in order to interact with them. For example, cats have a mild affiliative response of slowly closing their eyes; humans often mimic this signal towards a pet cat to establish a tolerant relationship. Stroking, petting and rubbing pet animals are all actions that probably work through their natural patterns of interspecific communication.

Dogs have shown an ability to understand human communication. In object choice tasks, dogs utilize human communicative gestures such as pointing and direction of gaze in order to locate hidden food and toys.^[34] It has also been shown that dogs exhibit a left gaze bias when looking at human faces, indicating that they are capable of reading human emotions.^[35] It is interesting to note that dogs do not make use of direction of gaze or exhibit left gaze bias with other dogs.

A new approach in the 21st century in the field of animal communication uses applied behavioural analysis (ABA), specifically Functional Communication Training (FCT). This FCT previously has been used in schools and clinics with humans with special needs, such as children with autism, to help them develop language. Sean Senechal, at the AnimalSign Center has been using an approach similar to this FCT with domesticated animals, such as dogs (since 2004) and horses (since 2000) with encouraging results and benefits to the animals and people. Functional communication training for animals, Senechal calls "AnimalSign Language". This includes teaching communication through gestures (like simplified American sign language), Picture Exchange Communication System, tapping, and vocalisation. The process for animals includes simplified and modified techniques.

Linguistics

For linguistics, the interest of animal communication systems lies in their similarities to and differences from human language:

1. Human languages are characterized for having a double articulation (in the characterization of French linguist André Martinet). It means that complex linguistic expressions can be broken down in meaningful elements (such as morphemes and words), which in turn are composed of smallest phonetic elements that affect meaning, called phonemes. Animal signals, however, do not exhibit this dual structure.
2. In general, animal utterances are responses to external stimuli, and do not refer to matters removed in time and space. Matters of relevance at a distance, such as distant food sources, tend to be indicated to other individuals by body language instead, for example wolf activity before a hunt, or the information conveyed in honeybee dance language.It is therefore unclear to what extent utterances are automatic responses and to what extent deliberate intent plays a part.
3. In contrast to human language, animal communication systems are usually not able to express conceptual generalizations. (Cetaceans and some primates may be notable exceptions).
4. Human languages combine elements to produce new messages (a property known as creativity). One factor in this is that much human language growth is based upon conceptual ideas and hypothetical structures, both being far greater capabilities in humans than animals. This appears far less common in animal communication systems, although current research into animal culture is still an ongoing process with many new discoveries.

A recent and interesting area of development is the discovery that the use of syntax in language, and the ability to produce "sentences", is not limited to humans either. The first good evidence of syntax in non-humans, reported^[37] in 2006, is from the greater spot-nosed monkey (Cercopithecus nictitans) of Nigeria. This is the first evidence that some animals can take discrete units of communication, and build them up into a sequence which then carries a different meaning from the individual "words":

The greater spot-nosed monkeys have two main alarm sounds. A sound known onomatopoeiacally as the "pyow" warns against a lurking leopard, and a coughing sound that scientists call a "hack" is used when an eagle is flying nearby.

"Observationally and experimentally we have demonstrated that this sequence [of up to three 'pyows' followed by up to four 'hacks'] serves to elicit group movement... the 'pyow-hack' sequence means something like 'let's go!' [a command telling others to move]... The implications are that primates at least may be able to ignore the usual relationship between an individual alarm call, and the meaning it might convey under certain circumstances... To our knowledge this is the first good evidence of a syntax-like natural communication system in a non-human species."

Similar results have also recently been reported in the Campbell's mona monkey.

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November 17, 2017
Original link:  http://www.kurzweilai.net/how-to-open-the-blood-brain-barrier-with-precision-for-safer-drug-delivery
 

Schematic representation of the feedback-controlled focused ultrasound drug delivery system. Serving as the acoustic indicator of drug-delivery dosage, the microbubble emission signal was sensed and compared with the expected value. The difference was used as feedback to the ultrasound transducer for controlling the level of the ultrasound transmission. The ultrasound transducer and sensor were located outside the rat skull. The microbubbles were generated in the bloodstream at the target location in the brain. (credit: Tao Sun/Brigham and Women’s Hospital; adapted by KurzweilAI)

Researchers at Brigham and Women’s Hospital have developed a safer way to use focused ultrasound to temporarily open the blood-brain barrier* to allow for delivering vital drugs for treating glioma brain tumors — an alternative to invasive incision or radiation.

Focused ultrasound drug delivery to the brain uses “cavitation” — creating microbubbles — to temporarily open the blood-brain barrier. The problem with this method has been that if these bubbles destabilize and collapse, they could damage the critical vasculature in the brain.

To create a finer degree of control over the microbubbles and improve safety, the researchers placed a sensor outside of the rat brain to listen to ultrasound echoes bouncing off the microbubbles, as an indication of how stable the bubbles were.** That data was used to modify the ultrasound intensity, stabilizing the microbubbles to maintain safe ultrasound exposure.

The team tested the approach in both healthy rats and in an animal model of glioma brain cancer. Further research will be needed to adapt the technique for humans, but the approach could offer improved safety and efficacy control for human clinical trials, which are now underway in Canada.

The research, published this week in the journal Proceedings of the National Academy of Sciences, was supported by the National Institutes of Health in Canada.

* The blood brain barrier is an impassable obstacle for 98% of drugs, which it treats as pathogens and blocks them from passing from patients’ bloodstream into the brain. Using focused ultrasound, drugs can administered using an intravenous injection of innocuous lipid-coated gas microbubbles.

** For the ultrasound transducer, the researchers combined two spherically curved transducers (operating at a resonant frequency at 274.3 kHz) to double the effective aperture size and provide significantly improved focusing in the axial direction.

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Abstract of Closed-loop control of targeted ultrasound drug delivery across the blood–brain/tumor barriers in a rat glioma model

Cavitation-facilitated microbubble-mediated focused ultrasound therapy is a promising method of drug delivery across the blood–brain barrier (BBB) for treating many neurological disorders. Unlike ultrasound thermal therapies, during which magnetic resonance thermometry can serve as a reliable treatment control modality, real-time control of modulated BBB disruption with undetectable vascular damage remains a challenge. Here a closed-loop cavitation controlling paradigm that sustains stable cavitation while suppressing inertial cavitation behavior was designed and validated using a dual-transducer system operating at the clinically relevant ultrasound frequency of 274.3 kHz. Tests in the normal brain and in the F98 glioma model in vivo demonstrated that this controller enables reliable and damage-free delivery of a predetermined amount of the chemotherapeutic drug (liposomal doxorubicin) into the brain. The maximum concentration level of delivered doxorubicin exceeded levels previously shown (using uncontrolled sonication) to induce tumor regression and improve survival in rat glioma. These results confirmed the ability of the controller to modulate the drug delivery dosage within a therapeutically effective range, while improving safety control. It can be readily implemented clinically and potentially applied to other cavitation-enhanced ultrasound therapies.

References:

• Tao Sun, Yongzhi Zhang, Chanikarn Power, Phillip M. Alexander, Jonathan T. Sutton, Muna Aryal, Natalia Vykhodtseva, Eric L. Miller, Nathan J. McDannold. Closed-loop control of targeted ultrasound drug delivery across the blood–brain/tumor barriers in a rat glioma model. Proceedings of the National Academy of Sciences, 2017; 201713328 DOI: 10.1073/pnas.1713328114

Related:

• Triggered by ultrasound, microbubbles open the blood-brain barrier to administer drugs without harming other areas of the body

Philosophy of biology

From Wikipedia, the free encyclopedia

The philosophy of biology is a subfield of philosophy of science, which deals with epistemological, metaphysical, and ethical issues in the biological and biomedical sciences. Although philosophers of science and philosophers generally have long been interested in biology (e.g., Aristotle, Descartes, and even Kant), philosophy of biology only emerged as an independent field of philosophy in the 1960s and 1970s. Philosophers of science then began paying increasing attention to biology, from the rise of Neodarwinism in the 1930s and 1940s to the discovery of the structure of DNA in 1953 to more recent advances in genetic engineering. Other key ideas include the reduction of all life processes to biochemical reactions, and the incorporation of psychology into a broader neuroscience.

Overview

The philosophy of biology can be seen as following an empirical tradition, favoring naturalism. Many contemporary philosophers of biology have largely avoided traditional questions about the distinction between life and non-life. Instead, they have examined the practices, theories, and concepts of biologists with a view toward better understanding biology as a scientific discipline (or group of scientific fields). Scientific ideas are philosophically analyzed and their consequences are explored. It is sometimes difficult to delineate philosophy of biology as separate from theoretical biology. A few of the questions philosophers of biology have attempted to answer, for example, include:

• "What is a biological species?"
• "How is rationality possible, given our biological origins?"
• "How do organisms coordinate their common behavior?"
• "Are there genome editing agents?"
• "How might our biological understandings of race, sexuality, and gender reflect social values?"
• "What is natural selection, and how does it operate in nature?"
• "How do medical doctors explain disease?"
• "From where do language and logic stem?"
• "How is ecology related to medicine?"

A subset of philosophers of biology with a more explicitly naturalistic orientation hope that biology will provide scientific answers to such fundamental problems of epistemology, ethics, aesthetics, anthropology and even metaphysics. Furthermore, progress in biology urges modern societies to rethink traditional values concerning all aspects of human life. The possibility of genetic modification of human stem cells, for example, has led to an ongoing controversy on how certain biological techniques could infringe upon ethical consensus (see bioethics). Some of the questions addressed by these philosophers of biology include:

• "What is life?"^[1]
• "What makes humans uniquely human?"
• "What is the basis of moral thinking?"
• "What are the factors we use for aesthetic judgments?"
• "Is evolution compatible with Christianity or other religious systems?"

Increasingly, ideas drawn from philosophical ontology and logic are being used by biologists in the domain of bioinformatics. Ontologies such as the Gene Ontology^[2] are being used to annotate the results of biological experiments in a variety of model organisms in order to create logically tractable bodies of data available for reasoning and search. The Gene Ontology itself is a species-neutral graph-theoretical representation of biological types joined together by formally defined relations.^[3]

Philosophy of biology today has become a very visible, well-organized discipline - with its own journals, conferences, and professional organizations. The largest of the latter is the International Society for the History, Philosophy, and Social Studies of Biology (ISHPSSB);^[4] the name of the Society reflecting the interdisciplinary nature of the field.

Reductionism, holism, and vitalism

One subject within philosophy of biology deals with the relationship between reductionism and holism, contending views with epistemological and methodological significance, but also with ethical and metaphysical connotations.

• Scientific reductionism is the view that higher-level biological processes reduce to physical and chemical processes. For example, the biological process of respiration is explained as a biochemical process involving oxygen and carbon dioxide.
• Holism is the view that emphasizes higher-level processes, also called emergent properties: phenomena at a larger level that occur due to the pattern of interactions between the elements of a system over time. For example, to explain why one species of finch survives a drought while others die out, the holistic method looks at the entire ecosystem. Reducing an ecosystem to its parts in this case would be less effective at explaining overall behavior (in this case, the decrease in biodiversity). As individual organisms must be understood in the context of their ecosystems, holists argue, so must lower-level biological processes be understood in the broader context of the living organism in which they take part. Proponents of this view cite our growing understanding of the multidirectional and multilayered nature of gene modulation (including epigenetic changes) as an area where a reductionist view is inadequate for full explanatory power.^[5] See also Holism in science.
• Vitalism is the view, rejected by mainstream biologists since the 19th century, that there is a life-force (called the "vis viva") that has thus far been unmeasurable scientifically that gives living organisms their "life." Vitalists often claimed that the vis viva acts with purposes according to its pre-established "form" (see teleology). Examples of vitalist philosophy are found in many religions. Mainstream biologists reject vitalism on the grounds that it opposes the scientific method. The scientific method was designed as a methodology to build an extremely reliable understanding of the world, that is, a supportable, evidenced understanding. Following this epistemological view, mainstream scientists reject phenomena that have not been scientifically measured or verified, and thus reject vitalism.

Some philosophers of biology have attempted to explain the rise and fall of reductionism, vitalism, and holism throughout the history of biology. For example, these philosophers claim that the ideas of Charles Darwin ended the last remainders of teleology in biology, though the matter continues to be debated. Debates in these areas of philosophy of biology turn on how one views reductionism.

An autonomous philosophy of biology

All processes in organisms obey physical laws, the difference from inanimate processes lying in their organisation and their being subject to control by coded information. This has led some biologists and philosophers (for example, Ernst Mayr and David Hull) to return to the strictly philosophical reflections of Charles Darwin to resolve some of the problems which confronted them when they tried to employ a philosophy of science derived from classical physics. This latter, positivist approach, exemplified by Joseph Henry Woodger, emphasised a strict determinism (as opposed to high probability) and to the discovery of universally applicable laws, testable in the course of experiment. It was difficult for biology, beyond a basic microbiological level, to live up to these structures.^[6] Standard philosophy of science seemed to leave out a lot of what characterised living organisms - namely, a historical component in the form of an inherited genotype.

Biologists with philosophic interests responded, emphasising the dual nature of the living organism. On the one hand there was the genetic programme (represented in nucleic acids) - the genotype. On the other there was its extended body or soma - the phenotype. In accommodating the more probabilistic and non-universal nature of biological generalisations, it was a help that standard philosophy of science was in the process of accommodating similar aspects of 20th century physics.

This led to a distinction between proximate causes and explanations - "how" questions dealing with the phenotype; and ultimate causes - "why" questions, including evolutionary causes, focused on the genotype. This clarification was part of the great reconciliation, by Ernst Mayr, among others, in the 1940s, between Darwinian evolution by natural selection and the genetic model of inheritance. A commitment to conceptual clarification has characterised many of these philosophers since. Trivially, this has reminded us of the scientific basis of all biology, while noting its diversity - from microbiology to ecology. A complete philosophy of biology would need to accommodate all these activities.^{[citation needed]} Less trivially, it has unpacked the notion of "teleology". Since 1859, scientists have had no need for a notion of cosmic teleology - a programme or a law that can explain and predict evolution. Darwin provided that. But teleological explanations (relating to purpose or function) have remained stubbornly useful in biology - from the structural configuration of macromolecules to the study of co-operation in social systems. By clarifying and restricting the use of the term to describe and explain systems controlled strictly scientifically by genetic programmes, or other physical systems, teleological questions can be framed and investigated while remaining committed to the physical nature of all underlying organic processes.

Similar attention has been given to the concepts of natural selection (what is the target of natural selection? - the individual? the environment? the genome? the species?); adaptation; diversity and classification; species and speciation; and macroevolution.

Just as biology has developed as an autonomous discipline in full conversation with the other sciences, there is a great deal of work now being carried on by biologists and philosophers to develop a dedicated philosophy of biological science which, while in full conversation with all other philosophic disciplines, attempts to give answers to the real questions raised by scientific investigations in biology.

Other perspectives

While the overwhelming majority of English-speaking scholars operating under the banner of "philosophy of biology" work within the Anglo-American tradition of analytical philosophy, there is a stream of philosophic work in continental philosophy which seeks to deal with issues deriving from biological science. The communication difficulties involved between these two traditions are well known, not helped by differences in language. Gerhard Vollmer is often thought of as a bridge but, despite his education and residence in Germany, he largely works in the Anglo-American tradition, particularly pragmatism, and is famous for his development of Konrad Lorenz's and Willard Van Orman Quine's idea of evolutionary epistemology. On the other hand, one scholar who has attempted to give a more continental account of the philosophy of biology is Hans Jonas. His "The Phenomenon of Life" (New York, 1966) sets out boldly to offer an "existential interpretation of biological facts", starting with the organism's response to stimulus and ending with man confronting the Universe, and drawing upon a detailed reading of phenomenology. This is unlikely to have much influence on mainstream philosophy of biology, but indicates, as does Vollmer's work, the current powerful influence of biological thought on philosophy. Another account is given by the late Virginia Tech philosopher Marjorie Grene.

Philosophy of biology was historically associated very closely with theoretical evolutionary biology, however more recently there have been more diverse movements within philosophy of biology including movements to examine for instance molecular biology.^[11]

Scientific discovery process

Research in biology continues to be less guided by theory than it is in other sciences.^[12] This is especially the case where the availability of high throughput screening techniques for the different "-omics" fields such as genomics, whose complexity makes them predominantly data-driven. Such data-intensive scientific discovery is by some considered to be the fourth paradigm, after empiricism, theory and computer simulation.^[13] Others reject the idea that data driven research is about to replace theory.^[14][15] As Krakauer et al. put it: "machine learning is a powerful means of preprocessing data in preparation for mechanistic theory building, but should not be considered the final goal of a scientific inquiry."^[16] In regard to cancer biology, Raspe et al. state: "A better understanding of tumor biology is fundamental for extracting the relevant information from any high throughput data." ^[17] The journal Science chose cancer immunotherapy as the breakthrough of 2013. According to their explanation a lesson to be learned from the successes of cancer immunotherapy is that they emerged from decoding of basic biology.^[18]

Theory in biology is to some extent less strictly formalized than in physics. Besides 1) classic mathematical-analytical theory, as in physics, there is 2) statistics-based, 3) computer simulation and 4) conceptual/verbal analysis.^[19] Dougherty and Bittner argue that for biology to progress as a science, it has to move to more rigorous mathematical modeling, or otherwise risk to be "empty talk".^[20]
 
In tumor biology research, the characterization of cellular signaling processes has largely focused on identifying the function of individual genes and proteins. Janes ^[21] showed however the context-dependent nature of signaling driving cell decisions demonstrating the need for a more system based approach.^[22] The lack of attention for context dependency in preclinical research is also illustrated by the observation that preclinical testing rarely includes predictive biomarkers that, when advanced to clinical trials, will help to distinguish those patients who are likely to benefit from a drug.

What Is Life?

From Wikipedia, the free encyclopedia

What Is Life? The Physical
Aspect of the Living Cell

Title pages of 1948 edition
Author	Erwin Schrödinger
Country	United Kingdom (UK)
Language	English
Genre	Popular science
Publisher	Cambridge University Press
Publication date	1944
Media type	Print
Pages	194 pp.
ISBN	0-521-42708-8
OCLC	24503223
Dewey Decimal	574/.01 20
LC Class	QH331 .S357 1992

What Is Life? The Physical Aspect of the Living Cell is a 1944 science book written for the lay reader by physicist Erwin Schrödinger. The book was based on a course of public lectures delivered by Schrödinger in February 1943, under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin. The lectures attracted an audience of about 400, who were warned "that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist’s most dreaded weapon, mathematical deduction, would hardly be utilized." Schrödinger's lecture focused on one important question: "how can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?"

In the book, Schrödinger introduced the idea of an "aperiodic crystal" that contained genetic information in its configuration of covalent chemical bonds. In the 1950s, this idea stimulated enthusiasm for discovering the genetic molecule. Although the existence of some form of hereditary information had been hypothesized since 1869, its role in reproduction and its helical shape were still unknown at the time of Schrödinger's lecture. In retrospect, Schrödinger's aperiodic crystal can be viewed as a well-reasoned theoretical prediction of what biologists should have been looking for during their search for genetic material. Both James D. Watson,^[2] and Francis Crick, who jointly proposed the double helix structure of DNA based on X-ray diffraction experiments by Rosalind Franklin, credited Schrödinger's book with presenting an early theoretical description of how the storage of genetic information would work, and each independently acknowledged the book as a source of inspiration for their initial researches.^[3]

Background

The book is based on lectures delivered under the auspices of the Institute at Trinity College, Dublin, in February 1943 and published in 1944. At that time DNA was not yet accepted as the carrier of hereditary information, which only was the case after the Hershey–Chase experiment of 1952. One of the most successful branches of physics at this time was statistical physics, and quantum mechanics, a theory which is also very statistical in its nature. Schrödinger himself is one of the founding fathers of quantum mechanics.

Max Delbrück's thinking about the physical basis of life was an important influence on Schrödinger.^[4] However, long before the publication of What is Life?, geneticist and 1946 Nobel-prize winner H. J. Muller had in his 1922 article "Variation due to Change in the Individual Gene"^[5] already laid out all the basic properties of the "heredity molecule" (then not yet known to be DNA) that Schrödinger was to re-derive in 1944 "from first principles" in What is Life? (including the "aperiodicity" of the molecule), properties which Muller specified and refined additionally in his 1929 article "The Gene As The Basis of Life"^[6] and during the 1930s.^[7] Moreover, H. J. Muller himself wrote in a 1960 letter to a journalist regarding What Is Life? that whatever the book got right about the "hereditary molecule" had already been published before 1944 and that Schrödinger's were only the wrong speculations; Muller also named two famous geneticists (including Delbrück) who knew every relevant pre-1944 publication and had been in contact with Schrödinger before 1944. But DNA as the molecule of heredity became topical only after Oswald Avery's most important bacterial-transformation experiments in 1944. Before these experiments, proteins were considered the most likely candidates.

Content

In chapter I, Schrödinger explains that most physical laws on a large scale are due to chaos on a small scale. He calls this principle "order-from-disorder." As an example he mentions diffusion, which can be modeled as a highly ordered process, but which is caused by random movement of atoms or molecules. If the number of atoms is reduced, the behaviour of a system becomes more and more random. He states that life greatly depends on order and that a naïve physicist may assume that the master code of a living organism has to consist of a large number of atoms.

In chapter II and III, he summarizes what was known at this time about the hereditary mechanism. Most importantly, he elaborates the important role mutations play in evolution. He concludes that the carrier of hereditary information has to be both small in size and permanent in time, contradicting the naïve physicist's expectation. This contradiction cannot be resolved by classical physics.

In chapter IV, Schrödinger presents molecules, which are indeed stable even if they consist of only a few atoms, as the solution. Even though molecules were known before, their stability could not be explained by classical physics, but is due to the discrete nature of quantum mechanics. Furthermore, mutations are directly linked to quantum leaps.

He continues to explain, in chapter V, that true solids, which are also permanent, are crystals. The stability of molecules and crystals is due to the same principles and a molecule might be called "the germ of a solid." On the other hand, an amorphous solid, without crystalline structure, should be regarded as a liquid with a very high viscosity. Schrödinger believes the heredity material to be a molecule, which unlike a crystal does not repeat itself. He calls this an aperiodic crystal. Its aperiodic nature allows it to encode an almost infinite number of possibilities with a small number of atoms. He finally compares this picture with the known facts and finds it in accordance with them.
In chapter VI Schrödinger states:

…living matter, while not eluding the "laws of physics" as established up to date, is likely to involve "other laws of physics" hitherto unknown, which however, once they have been revealed, will form just as integral a part of science as the former.

He knows that this statement is open to misconception and tries to clarify it. The main principle involved with "order-from-disorder" is the second law of thermodynamics, according to which entropy only increases in a closed system (such as the universe). Schrödinger explains that living matter evades the decay to thermodynamical equilibrium by homeostatically maintaining negative entropy (today this quantity is called information^[8]) in an open system.

In chapter VII, he maintains that "order-from-order" is not absolutely new to physics; in fact, it is even simpler and more plausible. But nature follows "order-from-disorder", with some exceptions as the movement of the celestial bodies and the behaviour of mechanical devices such as clocks. But even those are influenced by thermal and frictional forces. The degree to which a system functions mechanically or statistically depends on the temperature. If heated, a clock ceases to function, because it melts. Conversely, if the temperature approaches absolute zero, any system behaves more and more mechanically. Some systems approach this mechanical behaviour rather fast with room temperature already being practically equivalent to absolute zero.

Schrödinger concludes this chapter and the book with philosophical speculations on determinism, free will, and the mystery of human consciousness. He attempts to "see whether we cannot draw the correct non-contradictory conclusion from the following two premises: (1) My body functions as a pure mechanism according to Laws of Nature; and (2) Yet I know, by incontrovertible direct experience, that I am directing its motions, of which I foresee the effects, that may be fateful and all-important, in which case I feel and take full responsibility for them. The only possible inference from these two facts is, I think, that I – I in the widest meaning of the word, that is to say, every conscious mind that has ever said or felt 'I' – am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature" Schrödinger then states that this insight is not new and that Upanishads considered this insight of "ATHMAN = BRAHMAN" to "represent quintessence of deepest insights into the happenings of the world. Schrödinger rejects the idea that the source of consciousness should perish with the body because he finds the idea "distasteful". He also rejects the idea that there are multiple immortal souls that can exist without the body because he believes that consciousness is nevertheless highly dependent on the body. Schrödinger writes that, to reconcile the two premises,

The only possible alternative is simply to keep to the immediate experience that consciousness is a singular of which the plural is unknown; that there is only one thing and that what seems to be a plurality is merely a series of different aspects of this one thing…

Any intuitions that consciousness is plural, he says, are illusions. Schrödinger is sympathetic to the Hindu concept of Brahman, by which each individual's consciousness is only a manifestation of a unitary consciousness pervading the universe — which corresponds to the Hindu concept of God. Schrödinger concludes that "…'I' am the person, if any, who controls the 'motion of the atoms' according to the Laws of Nature." However, he also qualifies the conclusion as "necessarily subjective" in its "philosophical implications". In the final paragraph, he points out that what is meant by "I" is not the collection of experienced events but "namely the canvas upon which they are collected." If a hypnotist succeeds in blotting out all earlier reminiscences, he writes, there would be no loss of personal existence — "Nor will there ever be."^[9]

Schrödinger's "paradox"

In a world governed by the second law of thermodynamics, all isolated systems are expected to approach a state of maximum disorder. Since life approaches and maintains a highly ordered state, some argue that this seems to violate the aforementioned second law, implying that there is a paradox. However, since the biosphere is not an isolated system, there is no paradox. The increase of order inside an organism is more than paid for by an increase in disorder outside this organism by the loss of heat into the environment. By this mechanism, the second law is obeyed, and life maintains a highly ordered state, which it sustains by causing a net increase in disorder in the Universe. In order to increase the complexity on Earth—as life does—free energy is needed and in this case is provided by the Sun.^[10][11]

Editions

• Erwin Schrödinger (1944), "What Is Life? : The Physical Aspect of the Living Cell". Based on lectures delivered under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin, in February 1943.