Models of neural computation are attempts to elucidate, in an
abstract and mathematical fashion, the core principles that underlie
information processing in biological nervous systems, or functional
components thereof. This article aims to provide an overview of the most
definitive models of neuro-biological computation as well as the tools
commonly used to construct and analyze them.
Introduction
Due
to the complexity of nervous system behavior, the associated
experimental error bounds are ill-defined, but the relative merit of the
different models
of a particular subsystem can be compared according to how closely they
reproduce real-world behaviors or respond to specific input signals. In
the closely related field of computational neuroethology, the practice is to include the environment in the model in such a way that the loop is closed.
In the cases where competing models are unavailable, or where only
gross responses have been measured or quantified, a clearly formulated
model can guide the scientist in designing experiments to probe
biochemical mechanisms or network connectivity.
In all but the simplest cases, the mathematical equations that
form the basis of a model cannot be solved exactly. Nevertheless,
computer technology, sometimes in the form of specialized software or
hardware architectures, allow scientists to perform iterative
calculations and search for plausible solutions. A computer chip or a
robot that can interact with the natural environment in ways akin to the
original organism is one embodiment of a useful model. The ultimate
measure of success is however the ability to make testable predictions.
General criteria for evaluating models
Speed of information processing
The
rate of information processing in biological neural systems are
constrained by the speed at which an action potential can propagate down
a nerve fibre. This conduction velocity ranges from 1 m/s to over
100 m/s, and generally increases with the diameter of the neuronal
process. Slow in the timescales of biologically-relevant events dictated
by the speed of sound or the force of gravity, the nervous system
overwhelmingly prefers parallel computations over serial ones in
time-critical applications.
Robustness
A
model is robust if it continues to produce the same computational
results under variations in inputs or operating parameters introduced by
noise. For example, the direction of motion as computed by a robust motion detector would not change under small changes of luminance, contrast
or velocity jitter. For simple mathematical models of neuron, for
example the dependence of spike patterns on signal delay is much weaker
than the dependence on changes in "weights" of interneuronal
connections.
Gain control
This
refers to the principle that the response of a nervous system should
stay within certain bounds even as the inputs from the environment
change drastically. For example, when adjusting between a sunny day and a
moonless night, the retina changes the relationship between light level
and neuronal output by a factor of more than so that the signals sent to later stages of
the visual system always remain within a much narrower range of amplitudes.
Linearity versus nonlinearity
A linear
system is one whose response in a specified unit of measure, to a set
of inputs considered at once, is the sum of its responses due to the
inputs considered individually.
Linear
systems are easier to analyze mathematically and are a persuasive
assumption in many models including the McCulloch and Pitts neuron,
population coding models, and the simple neurons often used in Artificial neural networks.
Linearity may occur in the basic elements of a neural circuit such as
the response of a postsynaptic neuron, or as an emergent property of a
combination of nonlinear subcircuits.
Though linearity is often seen as incorrect, there has been recent work
suggesting it may, in fact, be biophysically plausible in some cases.
Examples
A computational neural model may be constrained to the level of biochemical signalling in individual neurons or it may describe an entire organism in its environment. The examples here are grouped according to their scope.
The most widely used models of information transfer in biological
neurons are based on analogies with electrical circuits. The equations
to be solved are time-dependent differential equations with
electro-dynamical variables such as current, conductance or resistance,
capacitance and voltage.
The FitzHugh–Nagumo model is a simplication of the Hodgkin–Huxley model. The Hindmarsh–Rose model
is an extension which describes neuronal spike bursts. The Morris–Lecar
model is a modification which does not generate spikes, but describes
slow-wave propagation, which is implicated in the inhibitory synaptic
mechanisms of central pattern generators.
This approach, influenced by control theory and signal processing, treats neurons and synapses as time-invariant entities that produce outputs that are linear combinations of input signals, often depicted as sine waves with a well-defined temporal or spatial frequencies.
The entire behavior of a neuron or synapse are encoded in a transfer function,
lack of knowledge concerning the exact underlying mechanism
notwithstanding. This brings a highly developed mathematics to bear on
the problem of information transfer.
The accompanying taxonomy of linear filters turns out to be useful in characterizing neural circuitry. Both low- and high-pass filters
are postulated to exist in some form in sensory systems, as they act to
prevent information loss in high and low contrast environments,
respectively.
Indeed, measurements of the transfer functions of neurons in the horseshoe crab
retina according to linear systems analysis show that they remove
short-term fluctuations in input signals leaving only the long-term
trends, in the manner of low-pass filters. These animals are unable to
see low-contrast objects without the help of optical distortions caused
by underwater currents.
Models of computations in sensory systems
Lateral inhibition in the retina: Hartline–Ratliff equations
In
the retina, an excited neural receptor can suppress the activity of
surrounding neurons within an area called the inhibitory field. This
effect, known as lateral inhibition, increases the contrast and sharpness in visual response, but leads to the epiphenomenon of Mach bands. This is often illustrated by the optical illusion of light or dark stripes next to a sharp boundary between two regions in an image of different luminance.
The Hartline-Ratliff model describes interactions within a group of pphotoreceptor cells. Assuming these interactions to be linear, they proposed the following relationship for the steady-state response rate of the given p-th photoreceptor in terms of the steady-state response rates of the j surrounding receptors:
.
Here,
is the excitation of the target p-th receptor from sensory transduction
is the associated threshold of the firing cell, and
is the coefficient of inhibitory interaction between the p-th and the jth receptor. The inhibitory interaction decreases with distance from the target p-th receptor.
Cross-correlation in sound localization: Jeffress model
According to Jeffress, in order to compute the location of a sound source in space from interaural time differences, an auditory system relies on delay lines: the induced signal from an ipsilateral
auditory receptor to a particular neuron is delayed for the same time
as it takes for the original sound to go in space from that ear to the
other. Each postsynaptic cell is differently delayed and thus specific
for a particular inter-aural time difference. This theory is equivalent
to the mathematical procedure of cross-correlation.
Following Fischer and Anderson, the response of the postsynaptic neuron to the signals from the left and right ears is given by
where
and
represents the delay function. This is not entirely correct and a clear eye is needed to put the symbols in order.
Structures have been located in the barn owl which are consistent with Jeffress-type mechanisms.
Cross-correlation for motion detection: Hassenstein–Reichardt model
A motion detector needs to satisfy three general requirements: pair-inputs, asymmetry and nonlinearity.
The cross-correlation operation implemented asymmetrically on the
responses from a pair of photoreceptors satisfies these minimal
criteria, and furthermore, predicts features which have been observed in
the response of neurons of the lobula plate in bi-wing insects.
The master equation for response is
The HR model predicts a peaking of the response at a particular
input temporal frequency. The conceptually similar Barlow–Levick model
is deficient in the sense that a stimulus presented to only one receptor
of the pair is sufficient to generate a response. This is unlike the HR
model, which requires two correlated signals delivered in a time
ordered fashion. However the HR model does not show a saturation of
response at high contrasts, which is observed in experiment. Extensions
of the Barlow-Levick model can provide for this discrepancy.
Watson–Ahumada model for motion estimation in humans
This uses a cross-correlation in both the spatial and temporal directions, and is related to the concept of optical flow.
Neurophysiological metronomes: neural circuits for pattern generation
Mutually inhibitory processes are a unifying motif of all central pattern generators. This has been demonstrated in the stomatogastric (STG) nervous system of crayfish and lobsters.
Two and three-cell oscillating networks based on the STG have been
constructed which are amenable to mathematical analysis, and which
depend in a simple way on synaptic strengths and overall activity,
presumably the knobs on these things. The mathematics involved is the theory of dynamical systems.
Feedback and control: models of flight control in the fly
Flight control in the fly is believed to be mediated by inputs from the visual system and also the halteres, a pair of knob-like organs which measure angular velocity. Integrated computer models of Drosophila, short on neuronal circuitry but based on the general guidelines given by control theory and data from the tethered flights of flies, have been constructed to investigate the details of flight control.
In this approach the strength and type, excitatory or inhibitory, of
synaptic connections are represented by the magnitude and sign of
weights, that is, numerical coefficients in front of the inputs to a particular neuron. The response of the -th neuron is given by a sum of nonlinear, usually "sigmoidal" functions of the inputs as:
.
This response is then fed as input into other neurons and so on.
The goal is to optimize the weights of the neurons to output a desired
response at the output layer respective to a set given inputs at the
input layer. This optimization of the neuron weights is often performed
using the backpropagation algorithm and an optimization method such as gradient descent or Newton's method of optimization.
Backpropagation compares the output of the network with the expected
output from the training data, then updates the weights of each neuron
to minimize the contribution of that individual neuron to the total
error of the network.
Genetic algorithms
Genetic algorithms
are used to evolve neural (and sometimes body) properties in a model
brain-body-environment system so as to exhibit some desired behavioral
performance. The evolved agents can then be subjected to a detailed
analysis to uncover their principles of operation. Evolutionary
approaches are particularly useful for exploring spaces of possible
solutions to a given behavioral task because these approaches minimize a
priori assumptions about how a given behavior ought to be instantiated.
They can also be useful for exploring different ways to complete a
computational neuroethology model when only partial neural circuitry is
available for a biological system of interest.
NEURON
The NEURON software, developed at Duke University, is a simulation environment for modeling individual neurons and networks of neurons. The NEURON environment is a self-contained environment allowing interface through its GUI or via scripting with hoc or python.
The NEURON simulation engine is based on a Hodgkin–Huxley type model
using a Borg–Graham formulation. Several examples of models written in
NEURON are available from the online database ModelDB.
Embodiment in electronic hardware
Conductance-based silicon neurons
Nervous systems differ from the majority of silicon-based computing devices in that they resemble analog computers (not digital data processors) and massively parallel processors, not sequential processors. To model nervous systems accurately, in real-time, alternative hardware is required.
The most realistic circuits to date make use of analog properties of existing digital electronics (operated under non-standard conditions) to realize Hodgkin–Huxley-type models in silico.
Subversion (from Latinsubvertere'overthrow') refers to a process by which the values and principles of a system in place are contradicted or reversed in an attempt to sabotage the established social order and its structures of power, authority, tradition, hierarchy, and social norms.
Subversion can be described as an attack on the public morale and, "the
will to resist intervention are the products of combined political and
social or class loyalties which are usually attached to national
symbols. Following penetration, and parallel with the forced
disintegration of political and social institutions of the state, these
tendencies may be detached and transferred to the political or
ideological cause of the aggressor".
Subversion is used as a tool to achieve political goals because
it generally carries less risk, cost, and difficulty as opposed to open belligerency. Furthermore, it is a relatively cheap form of warfare that does not require large amounts of training. A subversive
is something or someone carrying the potential for some degree of
subversion. In this context, a "subversive" is sometimes called a "traitor"
with respect to (and usually by) the government in power. Subversion is
also often a goal of comedians, artists and people in those careers. In this case, being subversive can mean questioning, poking fun at, and undermining the established order in general.
Terrorist
groups generally do not employ subversion as a tool to achieve their
goals. Subversion is a manpower-intensive strategy and many groups lack
the manpower and political and social connections to carry out
subversive activities.
However, actions taken by terrorists may have a subversive effect on
society. Subversion can imply the use of insidious, dishonest, monetary,
or violent methods to bring about such change. This is in contrast to protest, a coup d'état,
or working through traditional means in a political system to bring
about change. Furthermore, external subversion is where, "the aggressor
state attempts to recruit and assist indigenous political and military
actors to overthrow their government by coup d’état".
If subversion fails in its goal of bringing about a coup it is possible
that the actors and actions of the subversive group could transition to
insurrection, insurgency, and/or guerrilla warfare.
The word is present in all languages of Latin
origin, originally applying to such events as the military defeat of a
city. As early as the 14th century, it was being used in the English language with reference to laws, and in the 15th century came to be used with respect to the realm. The term has taken over from 'sedition' as the name for illicit rebellion,
though the connotations of the two words are rather different; sedition
suggesting overt attacks on institutions, subversion something much
more surreptitious, such as eroding the basis of belief in the status quo or setting people against each other.
Definition
The problem with defining the term subversion is that there is not a single definition that is universally accepted.[8]Charles Townshend
described subversion as a term "so elastic as to be virtually devoid of
meaning, and its use does little more than convey the enlarged sense of
the vulnerability of modern systems to all kinds of covert assaults." What follows are some of the many attempts to define the term:
"Subversion is the undermining or detachment of
the loyalties of significant political and social groups within the
victimized state, and their transference, under ideal conditions, to the
symbols and institutions of the aggressor."
"Subversion — Actions designed to undermine the
military, economic, psychological, or political strength or morale of a
governing authority."
"Subversive Activity — Anyone lending aid, comfort, and moral support to individuals, groups, or organizations that advocate the overthrow of incumbent
governments by force and violence is subversive and is engaged in
subversive activity. All willful acts that are intended to be
detrimental to the best interests of the government and that do not fall
into the categories of treason, sedition, sabotage, or espionage will be placed in the category of subversive activity."
"Subversive Political Action — A planned series of
activities designed to accomplish political objectives by influencing,
dominating, or displacing individuals or groups who are so placed as to
affect the decisions and actions of another government."
Subversion — "A destructive, aggressive activity aimed to destroy the country, nation,
or geographical area of your enemy... [by demoralizing the cultural
values and changing the population's perception of reality].
Subversion — Roger Trinquier
defined subversion as a term that could be lumped together under the
name modern warfare, "as being interlocking systems of actions,
political, economic, psychological and military that aims at the
overthrow of established authority in a country."
Conceptual understanding
Defining
and understanding subversion means identifying entities, structures,
and things that can be subverted. Furthermore, it may help to identify
practices and tools that are not subversive. Institutions and morals can
be subverted, but ideology on the other hand cannot.
The fall of a government or the creation of a new government as a
result of an external war is not subversion. Espionage does not count as
subversion because it is not an action that leads directly to an
overthrow of a government. Information gathered from espionage may be
used to plan and carry out subversive activities.
To gain an understanding of what is considered to be subversive
requires understanding the intent of those taking action. This makes
defining and identifying subversion a difficult process. As Laurence
Beilenson points out, "To criticize a government in an effort to reform
it or to change its policies is not subversion, even though such
criticism may contribute to overthrow. But criticism intended to help a
projected overthrow becomes subversive without regard to whether it is
right or wrong."
Types
Subversion
can generally be broken down into internal and external subversion, but
this distinction is not meant to imply that each follows a specific set
of unique and separate tools and practices. Each subversive campaign is
different because of the social, political, economic, cultural, and
historical differences that each country has. Subversive activities are
employed based upon an evaluation of these factors. This breakdown
merely clarifies who the actors are. While the subversive actors may be
different, the soon to be subverted targets are the same. As Paul W. Blackstock
identifies, the ruling and political elites are the ultimate targets of
persuasion because they control the physical instruments of state
power.
Internal subversion is actions taken by those within a country
and can be used as a tool of power. In most cases the use or threat of
force is the last step of internal subversion.
External subversion is actions taken by another country in
cooperation with those inside the subverted country and can be used as a
tool of statecraft. Foreign volunteers from another country are not
enough to qualify for external subversion.
The reason for this is that the individuals may legitimately share the
cause of the internal subversive dissidents and have legitimately
volunteered. Only when the government itself furnishes a nation with
money, arms, supplies, or other help to dissidents can it be called
external subversion.
Generating civil unrest through demonstrations, strikes, and boycotts.
Other factors, while not specifically falling into these categories,
may also be useful to subversive dissidents. Additionally, many tools
may overlap into other groups of tools as well. As an example,
subversives may infiltrate an organization for cultural subversion more
so than for control. Civil unrest may be used to provoke the government
into a violent response.
Infiltration and establishing front groups
In
order for a group to be successful in subverting a government, the
group itself and its ideas must be seen as an acceptable alternative to
the status quo. However, groups that work toward subverting a
government, in many cases, follow ideas and promote goals that on their
surface would not receive the support of the population. Therefore, "to
gain public credibility, attract new supporters, generate revenue, and
acquire other resources, groups need to undertake political activities
that are entirely separate, or appear separate, from the overtly violent
activities of those groups. Sometimes this is achieved by infiltrating
political parties, labor unions, community groups, and charitable organizations."
Infiltrating organizations is an important tool because these
institutions are already seen as legitimate in the eyes of the people
and provide a platform to express their ideas. When infiltrating, the
dissident identifies needs of the organization and then links those
needs to solutions that his ideology can provide. This was a technique
that the Communist Party USA employed. Once the organization has been co-opted, the dissident can then move on to establishing ties with other groups.
Furthermore, in addition to gaining possible legitimacy for its ideas
the infiltration of these groups can "bolster political allies, attack
government policies, and attract international support."
If some organizations are too difficult to infiltrate, it may be
necessary to create new organizations that appear to be independent but
are actually under the direction of the subversive group.
The infiltration of state organizations can provide subversive
groups the opportunity to do many things to achieve their goals. The
infiltration of security forces can provide information about the
government's capabilities and how they plan to address the group's
activities. Infiltration also provides the opportunity to plant false
information, lead the government to misallocate resources, to steal
funds, weapons, equipment, and other resources, and ultimately aid in
weakening and delegitimizing the government.
The targets of infiltration are not limited to the groups and
institutions mentioned above. Economic industries and universities have
also been the target for infiltration. In the case of universities, the liberal arts departments are more prone to subversion than the hard sciences.
Russian and French methods
Dominique Poirier, former employee and specialist in communication warfare in the French intelligence service, DGSE, describes extensively subversion in a book on the practices and methods of this agency published in 2019,[25]
yet he rarely uses the noun "subversion", remarkably. While presenting
and describing extensively the Russian and French methods of subversion
and counter-subversion, he explains that the French intelligence
community in particular uses the term guerre de l’information,
or "information warfare". Then information warfare subsumes a number of
other nouns, sometimes of Russian origin, each denoting a specific
action that may actually describe an action of subversion or
counter-subversion. Coming to add to the latter difference in perception
of the action of subversion, he further says that information warfare
in the French intelligence community is ruled itself by active measures
that the DGSE, acting as leading intelligence agency in France, adopted
as an "all-encompassing" doctrine. Indeed, active measures in France
would regulate not only all intelligence and counterintelligence
activities, but also foreign affairs and diplomacy, domestic politics,
and even the activities of the major industrial and business companies
and groups in this country, since a period he locates between 1980 and
1982. For all the latter would be logically called to partake in a
common and coherent effort in intelligence, counterintelligence,
influence, and counterinfluence on the French soil as abroad. Actually,
the French intelligence community, and the DGSE in particular, always
use the nouns "interference" (French: ingérence) and "counterinterference" (contre-ingérence)
to name "subversion" and "counter-subversion" respectively.
The DGSE and one other intelligence agency of this country at least are
particularly active in subversive activities abroad, often in a joint
effort with the Russian foreign intelligence service, SVR RF,
with a focus on the United States, Dominique Poirier specifies from
firsthand knowledge and experience spanning the years 1980 to c. 2001.
In the latter context, the main methods of subversion he presents as
"actions of influence" and their expected results are the followings.
Most French and Russian actions of subversion, and of domestic influence alike, actually are governed by the notion of minority influence as initially defined by social psychologist Serge Moscovici. However, the DGSE in particular designs all such actions in accordance with fundamentals of a scientific approach akin to behaviorism, called "behavioral biology" (French: biologie comportementale) initially established in the early 1980s by French military scientist Henri Laborit.
Additionally, the narrative, or "formal aims" of the action of
subversion — when there is one, as behavioral biology focuses on acting
on the unconscious, or id, locating in the reptilian brain as defined by
Paul D. MacLean — is defined in accordance with fundamentals in epistemology, another Russian import in French information warfare and active measures.
The expression "awareness raising" "was a Soviet import that
occurred in France during the preparatory stage of the riots and general
strikes of May 1968. It happened in the early months of the latter
year, first as a sophisticated technique in agitprop known in the Soviet KGB under the name сенсибилизация (siencibilizatz’iya),
otherwise used in the other field of epistemology in Soviet Union. In
France, the latter Russian word was given definitively the translation
'sensibilisation' (without equivalent in English) circa March 1968, as
this word, sounding similar, already existed with other meanings in this
country. The latter facts explain why sensibilisation / 'awareness
raising' is the same in its principle as the other method of 'minority
influence' in agitprop." "An action of awareness raising
in active measures may aim to influence the opinion of the public in
one's own country or that of a foreign country or both, and its goal is
to make masses of people receptive to a concern that may be either true
and founded, or false and ill-founded in reality, or neither entirely
true and founded nor entirely false and ill-founded but "somewhere
between these two absolutes." The latter hypothesis, which often is
expected in active measures, is explained and ruled by the disciplines
of fuzzy logic and chaos theory, and generally aims to breed doubt, confusion, or inhibition, and then angst, discontent, or fear in the minds of people.
Remarkably, French experts in domestic influence and subversion use colloquially the noun "sleepwalkers" (French: somnanbules)
to call "all ordinary people composing the masses. The reason
justifying the choice of this noun, pejorative in a sense, is that an
overwhelming majority of ʻordinary peopleʼ are unable to tell the
difference between neutral, objective information (news) and propaganda
intended to influence. As seen from the viewpoint of specialists, the
whole population behaves as millions of 'sleepwalkers' ready to believe
anything the media, authors, and agents of influence tell and write,
indifferently. The reason explaining the naïveté is that people tend to
believe at its face value everything is formally published and
broadcast, by wrongly attributing some official and unanimously approved
virtue to media such as print and audiovisual periodical publications,
books, and similar. Then the greater the number of people truly or
apparently involved in the publishing / broadcasting of a fact or
fallacy is, the truer it seems to be in the understanding of the masses.
Additionally, the greater the known number of people who watched,
listened, or read the fact or fallacy is, the greater the probability is
that ʻit is true indeed,ʼ still in the understanding of the masses. ...
Moreover, in France, specialists in influence and counter-influence are
tasked to prevent the masses of people / 'sleepwalkers' from "waking
up" and understanding that they actually are thus fooled permanently,
and by which methods and tricks they are so, since their own country
fabricates and spreads fallacies for them either. In other words, about
the latter explanation, teaching the masses on methods and techniques in
foreign influence would be effective and salutary, doubtless, but at
the same time it would reveal to them the influence and propaganda that
their own government tailors and spreads for them. ... In the DGSE, a
rule alluding colloquially to this particular definition of sleepwalker
says, Ils dorment ; ne les réveillez pas ('They [the masses] sleep, don't wake them up'). Edgar Morin,
French communist philosopher, sociologist, intelligence officer, and
founder of modern methods and techniques of mass influence and
manipulation is at the origin of this particular use of the word
sleepwalker. Morin often said, "Eveillés, ils dorment" ('Awaken, they sleep'), quoting his own way Greek philosopher Heraclitus.
Thus, Morin implied that, as taken collectively, ordinary people who
constitute the masses are too stupid to make the difference between the
truth, influence, propaganda, and disinformation. For the record, the
exact and complete English translation of Morin's quote above is, "All
men do walk in sleep, and all have faith in that they dream: for all
things are as they seem to all, and all things flow like a stream."
Economics
Economics
can be both a tool of the internal and external subversive. For the
external subversive simply cutting off credit can cause severe economic
problems for a country. An example of this is the United States'
relations with Chile in the early 1970s. In an attempt to get Salvador Allende
removed from office, the United States tried to weaken the Chilean
economy. Chile received little foreign investments and the loss of
credit prevented Chile from purchasing vital imports.
An economic pressure of this kind prevents an economy from functioning
and reduces a country's standard of living. If the reduction is too
great, the people may become willing to support a change in the
government's leadership. The main objective of economic pressures is to
make it difficult for the country to fulfill its basic obligations to
the citizenry either by cutting off trade or by depriving it of
resources.
The internal subversive can also use economics to put pressure on
the government through use of the strike. An example of this is the
Chilean Truckers' Strike during the 1970s. The strike prevented the
transport of food staples and forced nearly 50% of the national economy
to cease production.
Activities of these kinds create human, economic, and political
problems that, if not addressed, can challenge the competency of the
government.
Agitation and civil unrest
As defined by Laurence Beilenson, agitation is "subversive propaganda
by action such as mass demonstrations or the political strike, that is,
a strike not intended to benefit the union or workers in the ordinary
sense, but intended instead against the government."
Furthermore, propaganda and agitation, even when they are legal forms
of freedom of speech, press, and assembly can still be classified as
subversive activity. These tools further demonstrate the need to
determine intent of those taking action to identify subversive
activities.
Civil unrest creates many of the problems that an insurgency
campaign does. First of all it is an affront to government authority,
and if the government is unable to quell the unrest it leads to an
erosion of state power. This loss of power stems from the people's lack
of trust in the government to maintain law and order. In turn, the
people begin to question whether or not new leadership is needed.
Discrediting, disarming, and demoralizing the government is the goal of these activities and the cause of the government's loss of power.
Civil unrest depletes resources as the government is forced to spend
more money on additional police. Additionally, civil unrest may be used
to provoke a response from the government. In the 1940s, during strikes
against the Marshall Plan,
communists in France would "deliberately provoke the police and
gendarmerie into acts of repressive violence in order to exploit the
resulting 'martyrs to the cause' for propaganda purposes." These martyrs
and subsequent propaganda can be useful in turning political and social
groups against each other. The less violent forms of unrest, "such as
worker absenteeism, passive resistance, boycotts, and deliberate
attempts to cripple government agencies by 'overloading the system' with
false reports, can have powerfully disruptive effects, both
economically and politically."
Offensive terror
Offensive
terror can be defined as the killing of people, destruction of
property, kidnapping, etc. It is usually a minor part of subversion and
"is used not to exert force in the transfer of state power, but is meant
to cower the people or ruler." Force used in this manner is meant to reinforce other forms or persuasion in addition to cowering the people or leaders.
Additionally, much like civil unrest and agitation, it raises the
question of whether or not the state can provide security for the
population. Terror also provides a practical motivation of physically
removing political opponents. The assassination of an organization's
leader may open the door to a successor that is more friendly to the
subversives position or possibly someone that has successfully
infiltrated the organization and is in fact one of the subversives.
Bribery
Bribery is one of the most common tools of subversion. Most societies see bribery as a form of corruption, and it used as a subversive tool because it "implies the undermining of existing rules of political or moral conduct."
It can also be one of the less reliable tools as well. Bribed officials
are only useful if they take action. However, actions taken over a
period of time draw suspicion from the public. The official must be able
to carefully conceal their actions or perform only key functions and
action. For these reasons, bribed officials are most effective when they
are asked to take immediate action. In the case of external subversion,
bribery is usually used for influence rather than for actions.
Theodor Adorno argued that the culture industry
and its shallow entertainment was a system by which society was
controlled through a top-down creation of standardized culture that
intensified the commodification of artistic expression; in 1938, he said
that capitalism has colonized every aspect of life so much that "every
pleasure which emancipates itself from the exchange-value takes on
subversive features."
Using culture to bring about change to a political system through integration of political warfare and political action and the targeting of cultural vehicles and institutions is another tool of subversion.
The use of the arts or more broadly culture is primarily a tool for
external subversives, as internal subversives are generally citizens of
the country and share the same culture. It is a tool that takes a longer
period of time to implement and its effects are revealed over time, as
opposed to those of a terrorist attack or civil unrest. Therefore, one
could classify this tool as an element of strategic subversion. The
targets of cultural subversive activities are traditionally film,
literature, popular music, educational institutions, mass media,
religious organizations, charitable organizations, and other forms of
art. The intended results of these activities are to persuade or co-opt
publics, discredit the ideas of enemies and splitting factions within
the enemy's camp.
The state is charged with the protection of the civilizational
values of society (liberty, equality, comradeship, compassion,
democracy, education, the family, religion, rule of law, human and civil
rights, etc.), "including the cultural/aesthetic values that enhance
the quality of life and maintain its legitimacy."
In situations where the government is not being a good steward in
protecting these values, the use of tools like literature, film, music
can be used as a reminder of these values, as well as a forum to protest
and question the government's legitimacy. Additionally, art and culture
allow people to connect on an emotional level that could soften
negative perceptions one may be believed to have. Once the stigma has
been removed, the target may be more receptive to other messages
conveyed. This individual or group would no longer be seen as being
completely different from them. Another example of how culture can be
subversive is seen in Iran. Western culture, media, art, etc. is popular
among the country's youth, but certain elements are banned or
curtailed. As the exportation of Western culture continues, conflict
between the state and its citizens is created. The government is then
seen as unresponsive or out of touch with its people.
Laws
Subversive activity
Subversive activity
is the lending of aid, comfort, and moral support to individuals,
groups, or organizations that advocate the overthrow of incumbent
governments by force and violence. All willful acts that are intended to
be detrimental to the best interests of the government and that do not
fall into the categories of treason, sedition, diversion, sabotage, or espionage are placed in the category of subversive activity.
Subversion (Chinese: 颠覆; pinyin: Diānfù) is a crime in Mainland China. The Government of the People's Republic of China prosecutes subversives under Articles 102 through 112 of the state criminal law. These articles specify the types of behavior that constitute a threat to national security and China has prosecuted many dissidents including Nobel Peace Prize laureate Liu Xiaobo using these laws. Of these, Articles 105 and 111 are the ones most commonly employed to silence political dissent.
Article 105 criminalizes organizing, plotting, or carrying out
subversion of the national order, or using rumor mongering or defamation
or other means to incite subversion of the national order or the
overthrow of the socialist system. Article 111 prohibits stealing, secretly collecting, purchasing, or illegally providing state secrets or intelligence to an organization, institution, or personnel outside the country.
There is no crime defined as "subversion" (as opposed to treason) in British constitutional law. Attempts have been made to introduce definitions but there is no general consensus among political and legal theorists.
Historically MI5 were entrusted with the legal investigative powers for concerns of threats to national security by subversion, but in the Security Service Act 1989,
subversion was not mentioned, and according to the official MI5
website, subversion is no longer investigated, due to a reduced threat
as a result of the end of the Cold War and of associated political situations since the 1980s.
United States
In federal law, 18 U.S.C.ch. 115 covers "Treason, Sedition, and Subversive Activities."
As related above, members of the Communist Party were supposed by legislators to be subversives, especially after the Russian Revolution. The House Un-American Activities Committee
was formed in 1938 in order to investigate alleged disloyalty and
subversive activities on the part of private citizens, public employees,
and those organizations suspected of having Communist ties. Senator Joseph McCarthy
became the most visible public face of a period in which Cold War
tensions fueled fears of widespread Communist subversion. The term "McCarthyism,"
coined in 1950 in reference to McCarthy's practices, including public
attacks on the character or patriotism of political opponents, was soon
applied to similar anti-communist activities. Senator Pat McCarran sponsored the McCarran Internal Security Act of 1950 and the Immigration and Nationality Act of 1952, both of which were hotly contested in the law courts, and by Harry Truman, who went so far as to veto the former; however, the veto was overridden in the Senate by a margin of 57 to 10.
Elfbrandt v. Russell involved questions concerning the constitutionality of an Arizona Act requiring an oath from state employees. William O. Douglas
wrote in 1966 for a strongly divided court the majority opinion that
the State could not require the oath and accompanying statutory gloss.
The Warren court ruled by 5–4 majority in Keyishian v. Board of Regents (of SUNY) to strike down New York
State law that prohibited membership by professors in any organization
that advocated the overthrow of the US government or any organization
that was held by the Regents to be "treasonous" or "seditious." The
Regents also required teachers and employees to sign an oath that they
were not members of the Communist Party.
Iran
Subversion (Persian: براندازی, romanized: barandāzi) is a crime in Iran. The government of Islamic Republic of Iran prosecutes subversives under Articles 498 through 500, 507 and 508 of Iran's criminal laws.
Constructive neutral evolution(CNE) is a theory that seeks to explain how complex systems can evolve through neutral transitions and spread through a population by chance fixation (genetic drift). Constructive neutral evolution is a competitor for both adaptationist
explanations for the emergence of complex traits and hypotheses
positing that a complex trait emerged as a response to a deleterious
development in an organism. Constructive neutral evolution often leads to irreversible or "irremediable" complexity
and produces systems which, instead of being finely adapted for
performing a task, represent an excess complexity that has been
described with terms such as "runaway bureaucracy" or even a "Rube Goldberg machine".
The groundworks for the concept of CNE were laid by two papers in
the 1990s, although first explicitly proposed by Arlin Stoltzfus in
1999. The first proposals for the role CNE was in the evolutionary origins of complex macromolecular machines such as the spliceosome, RNA editing machinery, supernumerary ribosomal proteins, chaperones, and more. Since then and as an emerging trend of studies in molecular evolution, CNE has been applied to broader features of biology and evolutionary history including some models of eukaryogenesis, the emergence of complex interdependence in microbial communities, and de novo formation of functional elements from non-functional transcripts of junk DNA. Several approaches propose a combination of neutral and adaptive contributions in the evolutionary origins of various traits.
Many evolutionary biologists posit that CNE must be the null hypothesis
when explaining the emergence of complex systems to avoid assuming that
a trait arose for an adaptive benefit. A trait may have arisen
neutrally, even if later co-opted
for another function. This approach stresses the need for rigorous
demonstrations of adaptive explanations when describing the emergence of
traits. This avoids the "adaptationist fallacy" which assumes that all
traits emerge because they are adaptively favoured by natural selection.
Principles
Excess capacity, presuppression, and ratcheting
Conceptually,
there are two components A and B (e.g. two proteins) that interact with
each other. A, which performs a function for the system, does not
depend on its interaction with B for its functionality, and the
interaction itself may have randomly arisen in an individual with the
ability to disappear without an effect on the fitness of A. This present
yet currently unnecessary interaction is therefore called an "excess
capacity" of the system. A mutation may then occur which compromises the
ability of A to perform its function independently. However, the A:B
interaction that has already emerged sustains the capacity of A to
perform its initial function. Therefore, the emergence of the A:B
interaction "presuppresses" the deleterious nature of the mutation,
making it a neutral change in the genome that is capable of spreading
through the population via random genetic drift. Hence, A has gained a
dependency on its interaction with B.
In this case, the loss of B or the A:B interaction would have a
negative effect on fitness and so purifying selection would eliminate
individuals where this occurs. While each of these steps are
individually reversible (for example, A may regain the capacity to
function independently or the A:B interaction may be lost), a random
sequence of mutations tends to further reduce the capacity of A to
function independently and a random walk through the dependency space
may very well result in a configuration in which a return to functional
independence of A is far too unlikely to occur, making CNE a
one-directional or "ratchet-like" process.
Biases on the production of variation
CNE
models of systematic complexification may rely crucially on some
systematic bias in the generation of variation. This is explained
relative to the original set of CNE models as follows:
In the gene-scrambling and RNA pan-editing cases, and in
the fragmentation of introns, the initial state of the system
(unscrambled, unedited, unfragmented) is unique or rare with regard to
some extensive set of combinatorial possibilities (scrambled, edited,
fragmented) that may be reached by mutation and (possibly neutral)
fixation. The resulting systemic bias drives a departure from the
improbable initial state to one of many alternative states. In the
editing model, a deletion:insertion mutational bias plays a subsidiary
role. In the gene duplication model, as well as in the explanation for
loss of self-splicing and for the origin of protein dependencies in
splicing, it is assumed that mutations that reduce activity or affinity
or stability are much more common than those with the opposite effect.
The resulting directionality consists in duplicate genes undergoing
reductions in activity, and introns losing self-splicing ability,
becoming dependent on available proteins as well as trans-acting intron
fragments.
That is, some of the models have a component of long-term
directionality that reflects biases in variation. A population-genetic
effect of bias in the introduction process, which appeared as a verbal
theory in the original CNE proposal, was later articulated and demonstrated formally (see Bias in the introduction of variation). This kind of effect does not require neutral evolution, lending credence to the suggestion
that the components of CNE models may be considered in a general theory
of complexification not specifically linked to neutrality.
Subfunctionalization
A case of CNE is subfunctionalization. The concept of subfunctionalization is that one original (ancestral) gene gives rise to two paralogous
copies of that gene, where each copy can only carry out part of the
function (or subfunction) of the original gene. First, a gene undergoes a
gene duplication
event. This event produces a new copy of the same gene known as a
paralog. After the duplication, deleterious mutations are accrued in
both copies of the gene. These mutations may compromise the capacity of
the gene to produce a product that can complete the desired function, or
it may result in the product fully losing one of its functions. In the
first scenario, the desired function may still be carried out because
the two copies of the gene together (as opposed to having only one) can
still produce sufficient product for the job. The organism is now
dependent on having two copies of this gene which are both slightly
degenerated versions of their ancestor. In the second scenario, the
genes may undergo mutations where they lose complementary functions.
That is to say, one protein may lose only one of its two functions
whereas the other protein only loses the other of its two functions. In
this case, the two genes now only carry out the individual subfunctions
of the original gene, and the organism is dependent on having each gene
to carry out each individual subfunction.
Paralogues that functionally interact to maintain the ancestral function can be termed "paralogous heteromers".
One high-throughput study confirmed that the rise of such interactions
between paralogous proteins as one possible long-term fate of paralogues
was frequent in yeast,
and the same study further found that paralogous heteromers accounted
for eukaryotic protein-protein interaction (PPI) networks. One specific
mechanism for the evolution of paralogous heteromers is by the
duplication of an ancestral protein interacting with other copies of
itself (homomers). To inspect the role of this process in the origins of
paralogous heteromers, it was found that ohnologs (paralogues that
arise from whole-genome duplications) that form paralogous heteromers in
Saccharomyces cerevisiae (budding yeast) are more likely to have homomeric orthologues than ohnologs in Schizosaccharomyces pombe. Similar patterns were found in the PPI networks of humans and the model plant Arabidopsis thaliana.
Examples of CNE
Identification and testability
To
positively identify features as having evolved through CNE, several
approaches are possible. The basic notion of CNE is that features which
have evolved through CNE are complex ones but do not provide an
advantage in fitness over their simpler ancestors. That is to say, an
unnecessary complexification has occurred. In some cases, phylogeny
can be used to inspect ancestral versions of systems and to see if
those ancestral versions were simpler and, if they were, if the rise in
complexity came with an advantage in fitness (i.e. acted as an
adaptation). While it is not straight forward to identify how adaptive
the emergence of a complex feature was, some methods are available. If
the more complex system has the same downstream effects in its
biochemical pathway as the ancestral and simpler system, this suggests
that the complexification did not carry with it any increase in fitness.
This approach is simpler when analyzing complex traits of which evolved
more recently and are taxonomically restricted in a few lineages
because "derived features can be more easily compared to their sisters
and inferred ancestors". The 'gold standard' approach for identifying cases of CNE involves direct experimentation, where ancestral versions of genes and systems are reconstructed and their properties directly identified. The first example of this involved analysis of components of a V-ATPase proton pump in fungal lineages.
RNA editing
RNA editing
systems have patchy phylogenetic distributions, indicating that they
are derived traits. RNA editing is required when a genome (most often
that of the mitochondria) needs to have its mRNA edited through various
substitutions, deletions, and insertions prior to translation. Guide RNA
molecules derived from separate semicircular strands of DNA provide the
correct sequence for the RNA editing complex to make the corresponding
edits. The RNA editing complex in Kinetoplastida
can comprise over 70 proteins in some taxonomically restricted
lineages, and mediate thousands of edits. Another taxonomically
restricted case of a different form of RNA editing system is found in
land plants. In kinetoplastids, RNA editing involves the addition of
thousands of nucleotides and deletion of several hundreds. However, the
necessity of this highly complex system is questionable. The large
majority of organisms do not rely on RNA editing systems, and in the
ones that do have it, the need for it is unclear as the optimal solution
would be for the DNA sequence to not contain the wrong (or missing)
nucleotides at several thousand sites to begin with. Furthermore, it is
difficult to argue that the RNA editing system emerged only in response
and to correct a genome faulty to this degree, as such a genome would
have been highly deleterious to the host and eliminated through purifying (negative) selection
to begin with. However, a scenario where a primitive RNA editing system
gratuitously arose prior to the introduction of errors into the genome
is more parsimonious. Once the RNA editing system arose, the original
mitochondrial genome would be able to tolerate previously deleterious
substitutions, deletions, and additions without an effect on fitness.
Once a sufficient number of these deleterious mutations took place, the
organism would by this point have developed a dependency on the RNA
editing system to faithfully correct any inaccurate sequences.
Spliceosomal complex
Few
if any evolutionary biologists believe that the initial spread of
introns through a genome and within the midst of a variety of genes
could have functioned as an evolutionary benefit for the organism in
question. Rather, the spread of an intron into a gene in an organism
without a spliceosome would be deleterious, and purifying selection
would eliminate individuals where this occurs. However, if a primitive
spliceosome emerged prior to the spread of introns into a hosts genome,
the subsequent spread of introns would not be deleterious as the
spliceosome would be capable of splicing out the introns and so allowing
the cell to accurately translate the messenger RNA transcript into a functional protein. The five small nuclear RNAs (snRNAs) that act to splice out introns from genes are thought to originate from group II introns,
and so it may be that these group II introns first spread and
fragmented into "five easy pieces" in a host where they formed small
trans-acting precursors to five modern and main snRNAs used in splicing.
These precursors had the capacity to splice out other introns within a
gene sequence, which then enabled introns to spread into genes without a
deleterious effect.
Microbial communities
Over
the course of evolution, many microbial communities have emerged where
individual species are not self-sufficient and require the mutualist
presence of other microbes to generate crucial nutrients for them. These
dependent microbes have experienced "adaptive gene loss" in the face of
being able to derive specific complex nutrients from their environment
instead of having to synthesize it directly. For this reason, many
microbes have developed complex nutritional requirements that have
prevented their cultivation in laboratory conditions. This highly
dependent state of many microbes on other organisms is similar to how
parasites undergo significant simplification when a large variety of
their nutritional needs are available from their hosts. J. Jeffrey
Morris and coauthors explained this through the "Black Queen
Hypothesis".
As a counterpart, W. Ford Doolittle and T. D. P. Brunet proposed the
"Gray Queen Hypothesis" to explain the emergence of these communities
with CNE. Initially, loss of genes required for synthesizing important
nutrients would be detrimental to the organism and so eliminated.
However, in the presence of other species where these nutrients are
freely available, mutations that degenerate the genes responsible for
synthesizing important nutrients are no longer deleterious because these
nutrients can simply be imported from the environment. Therefore, there
is a "presuppression" of the deleterious nature of these mutations.
Because these mutations are no longer deleterious, deleterious mutations
in these genes freely accumulate and render these organisms now
dependent on the presence of complementary microbes for supplying their
nutritional needs. This simplification of individual microbial species
in a community gives rise to a higher community-level complexity and
interdepence.
Null hypothesis
CNE has also been put forwards as the null hypothesis
for explaining complex structures, and thus adaptationist explanations
for the emergence of complexity must be rigorously tested on a
case-by-case basis against this null hypothesis prior to acceptance.
Grounds for invoking CNE as a null include that it does not presume that
changes offered an adaptive benefit to the host or that they were
directionally selected for, while maintaining the importance of more
rigorous demonstrations of adaptation when invoked so as to avoid the
excessive flaws of adaptationism criticized by Gould and Lewontin.
Eugene Koonin has argued that for evolutionary biology to be a
strictly "hard" science with a solid theoretical core, null hypotheses
need to be incorporated and alternatives need to falsify the null model
before being accepted. Otherwise, "just-so" adaptive stories may be
posited for the explanation of any trait or feature. For Koonin and
others, constructive neutral evolution plays the role as this null.
Sexuality in transgender individuals encompasses all the issues of sexuality of other groups, including establishing a sexual identity, learning to deal with one's sexual needs, and finding a partner, but may be complicated by issues of gender dysphoria, side effects of surgery, physiological and emotional effects of hormone replacement therapy, psychological aspects of expressing sexuality after medical transition, or social aspects of expressing their gender.
Sexual orientation
Historically, clinicians labelled trans people as heterosexual or homosexual relative to their sex assigned at birth.
Within the transgender community, sexual orientation terms based on
gender identity are the most common, and these terms include lesbian,
gay, bisexual, asexual, queer, and others.
Sexual orientation distribution
In the United States, transgender respondents to one 2015 survey self-identified as queer (21%), pansexual (18%), gay, lesbian, or same-gender-loving (16%), straight (15%), bisexual (14%), and asexual (10%).
A second study found 23% reported being gay, lesbian, or
same-gender-loving, 25% bisexual, 4% asexual, 23% queer, 23% straight
and 2% something else.
Transgender women
A 2015 survey of roughly 3,000 American trans women showed that at least 60% were attracted to women and 55% were attracted to men.
Of the trans women respondents 27% answered gay, lesbian, or
same-gender-loving, 20% answered bisexual, 19% heterosexual, 16%
pansexual, 6% answered asexual, 6% queer, and 6% did not answer.
Transgender men
Foerster reported a 15-year successful relationship between a woman and a trans man who transitioned in the late 1960s.
In the 20th century, trans men attracted to women struggled to demonstrate the existence and legitimacy of their identity. Many trans men attracted to women, such as jazz musician Billy Tipton, kept their trans status private until their deaths.
Until the mid-2010s, medical textbooks commonly suggested that most transgender men were straight.
However, a 2015 survey of roughly 2000 American trans men showed more
variation in sexual orientation or sexual identity among trans men. 23%
identified as heterosexual or straight. The vast majority (65%)
identified their sexual orientation or sexual identity as queer (24%),
pansexual (17%), bisexual (12%), gay/same-gender loving (12%), asexual
(7%), and 5% did not answer. Author Henry Rubin wrote that "[i]t took the substantial efforts of Lou Sullivan, a gay FTM activist who insisted that female-to-male transgender people could be attracted to men." Matt Kailey, author of Just Add Hormones: An Insider's Guide to the Transsexual Experience, recounts his transition "from 40-something straight woman to the gay man he'd always known himself to be." Researchers eventually acknowledged the existence of this phenomenon, and by the end of the 20th century, psychiatrist Ira Pauly
wrote, "The statement that all female-to-male transgender are
homosexual [Pauly means attracted to women] in their sexual preference
can no longer be made."
Trans gay men have varying levels of acceptance within other communities.
Psychiatrist Richard Green, in an appendix to Harry Benjamin's 1966 The Transsexual Phenomenon, considers people who were assigned male at birth who have adopted a more feminine gender role.
In this broad overview, entitled "Transsexualism: Mythological,
Historical, and Cross-Cultural Aspects", Green argues that the members
of these groups are mentally indistinguishable from modern western transsexual women. They have in common early effeminacy, adulthood femininity, and attraction to masculine males.
The Hijra of the Indian Subcontinent are people who were assigned male at birth but occupy a female sexual and/or gender role, sometimes undergoing castration.
As adults, they occupy a female role, but traditionally Hijra describe
themselves as neither male nor female, preferring Hijra as their gender. They often express their femininity in youth; as adults, they are usually sexually-oriented towards masculine men.
Mukhannathun
were transgender individuals of the Muslim faith and Arab extraction
who were present in Medina and Mecca during and after the time of
Muhammad.
Ibn Abd Al-Barh Al-Tabaeen, a companion of Aisha Umm ul-Mu'min'in who
knew the same mukhannath as Mohammed, stated that "If he is like this,
he would have no desire for women and he would not notice anything about
them. This is one of those who have no interest in women who were
permitted to enter upon women." That said, one of the Mukhannath of Medina during Muhammad's time had married a woman.
Cultural status
Beyond western cultures, sexual behavior and gender roles vary, which affects the place of gender variant people in that culture. Nadleehe of the North American Navajo hold a respected ceremonial position, whereas the Kathoey of Thailand experience more stigma comparatively.
In Iran, while sex change is somewhat accepted, the society is heteronormative.
As homosexuality is punishable by death, it is more common to see a
trans man being in a relationship with a woman and a trans woman in a
relationship with a man.
Mira Bellwether's self-published 2010 'zineFucking Trans Women was a landmark work in its focus on the perspectives and experiences of trans women, and has been described in Sexuality & Culture as "a comprehensive guide to trans women's sexuality". It focuses in particular on sex acts possible with flaccid penises and on the innervation of pre-op and non-op trans women's genital areas.It both named and popularized the act of muffing, or stimulating the inguinal canals through an invaginated scrotum, which can offer those with genital dysphoria a way to be penetrated from the front.
Cultural studies scholar J.R. Latham wrote the first definitive analysis of trans men's sexual practices in the journal Sexualities.
Few documentaries have been produced exploring transgender people's sexual practices.
Since 2013, creator Tobi Hill-Meyer has been working on a series of projects related to transgender peoples sexualities titled Doing it Again.
Research in areas of sexual behavior and experience is ongoing.
One study from 2020 conducted in Spain analyzed the sexual health and
behaviors of 260 participants.
Many transgender individuals choose to not use the language that is
typically used to refer to sexual body parts, instead using less
gendered words. The reason for this practice, is that hearing the
typical names for genitalia and other sexual body parts can cause severe
gender dysphoria for some trans people.
Not all transgender people choose to rename their bodies. Those
that choose not to rename their body, are often less uncomfortable with
their body and/or do not associate their sexual body parts with a gender
that differs from the one that they identify with. Ultimately, the
decision of what language a trans person chooses to use for their body,
and wants others to use, is up to the individual whose body is being
named.
Transgender women
Some trans women choose to refer to their anuses as a vagina, pussy, or cunt. (Cunt may also refer to either inguinal canal.) Terms used for the penis include junk, strapoff, strapless, clit, and hen.
Transgender men
Some trans men refer to their vaginas as their front holes because they find that term less gendered; some use terms like man cave, bonus hole, or boy cunt. Terms used for the clitoris include the dick, cock, dicklet, while the breasts may be called the chesticles.
Effects of transitioning
Effects of feminizing hormone therapy
For transgender women, taking estrogen
stimulates the development of breast tissue, causing them to increase
in both size and sensitivity. This increased sensitivity can be
pleasurable, painful, or both, depending on the person and the type of
stimulation. Furthermore, for those taking estrogen and who have male
genitalia, estrogen can (and often does) shrink the external male
genitalia and decrease the production of semen (at times bringing the
sperm count to zero), and can decrease the ability for the male
genitalia to become erect. In addition to these changes, some
transgender women going through hormone therapy
(HRT) can experience changes in the way their orgasms feel. For
example, some people report the ability to experience multiple orgasms.
HRT can cause decrease in sex drive or a change in the way arousal is experienced by trans women.
A study published in 2014 found that 62.4% of trans women surveyed
reported a decrease in sexual desire after hormone therapy and/or vaginoplasty. A 2008 study reported hypoactive sexual desire disorder
(HSDD) in as many as one in three post-operative trans women on HRT,
while around a quarter of the cisgender female controls were judged to
have the disorder. There was no difference between the two group's
reported sexual desire.
Some trans women and healthcare providers anecdotally report the use of progestogens increasing libido.
A 2009 pilot study tested the effectiveness of two treatments for
HSDD in trans women: transdermal testosterone and oral dydrogesterone
(a progestin).
After six weeks of treatment, the group treated with testosterone
reported improved sexual desire, while the group treated with the
progestin reported no change.
Effects of masculinizing hormone therapy
For transgender men, one of the most notable physical changes that many taking testosterone experience, in terms of sexuality and the sexual body, is the stimulation of clitoral tissue and the enlargement of the clitoris. This increase in size can range anywhere from just a slight increase to quadrupling in size. Other effects can include vaginal atrophy,
where the tissues of the vagina thin and may produce less lubrication.
This can make sex with the female genitalia more painful and can, at
times, result in bleeding. Transgender men taking testosterone are likely at increased risk of developing urinary tract infections, especially if they have receptive vaginal intercourse.
Other effects that testosterone can have on transgender men can
include an increase in their sex drive/libido. At times, this increase
can be very sudden and dramatic. Like transgender women, some
transgender men also experience changes in the way they experience
arousal.
Trans women who have undergone vaginoplasty must dilate in order to properly shape and form the neovagina. After several months, sexual intercourse can replace dilation, but if not sexually active, dilation is required again, for the rest of the patient's life.
Sexual orientation and transitioning
Some trans people maintain a consistent orientation throughout their lives, in some cases remaining with the same partner through transition.
A 2013 study found that 58.2 percent of its 452 transgender and
gender-nonconforming respondents experienced sexual attraction changes
during their lives, with trans masculine people more likely to
experience "sexual fluidity".
For transgender people who socially transitioned (about half of the
total sample), 64.4 percent experienced attraction changes after
transitioning, with trans feminine people more likely to experience
sexual fluidity.
A 2014 study of 70 trans women and 45 trans men had similar results,
with trans women more likely to experience a change in sexual
orientation (32.9 percent experienced changes versus 22.2 percent of
trans men).
In both groups of the 2014 study, trans people initially more attracted
to the opposite of the sex they were assigned at birth were
significantly more likely to experience sexual orientation changes (i.e.
trans men initially attracted to men and trans women initially
attracted to women changing their orientations). These sexual orientation changes could occur at any point in the transition process.
Some gynephilic trans women self-report that after transitioning,
they became sexually oriented towards males, and explain this as part
of their emerging female identity. Kurt Freund
hypothesized that such reports might reflect the desire of some trans
women to portray themselves as "typically feminine" or, alternatively,
might reflect their erotic interest in the validation provided by male
partners, rather than representing a genuine change in preference. A 2005 study which relied upon vaginal photoplethysmographies
to measure blood-flow in the genitalia of postoperative trans women
found they had arousal patterns which were category specific (i.e.
androphilic trans women were aroused by males, gynephilic trans women
were aroused by females) in a similar fashion to natal males, and argue
that vaginal photoplethysmographies are a useful technology for
measuring the validity of such reports. The one trans woman in the study
who reported a change in sexual orientation had arousal responses
consistent with her pre-reassignment sexual orientation.
While undergoing hormone therapy, some trans men report experiencing increased sexual attraction to cisgender men. This change can be confusing for those who experience it because it is often not a change that they expect to happen.
However, gender transition does not always mean sexual
orientation changes will happen. A 2021 study of 469 transgender women
and 433 transgender men found that sexual orientation did not change
over time or with hormonal transition.
Transvestic fetishism
The DSM once had a diagnosis of "transvestic fetishism". Some therapists and activists sought to de-pathologize this category in future revisions. DSM 5, which was released in 2013, replaced the transvestic fetishism category with "transvestic disorder".
Following the example of the Benjamin Scale, in 1979 Buhrich and
McConaghy proposed three clinically discrete categories of fetishistic
transvestism: "nuclear" transvestites who were satisfied with cross-dressing,
"marginal" transvestites who also desired feminization by hormones or
surgical intervention, and "fetishistic transsexuals", who had shown
fetishistic arousal but who identified as transsexuals and sought sex
reassignment surgery.
Sex work
In many cultures, transgender people (especially trans women) are frequently involved in sex work such as transgender pornography. This is correlated with employment discrimination.
In the 2011 National Trans Discrimination Survey, 11% of respondents
reported having done sex work for income, compared to 1% of cisgender
women in the US. According to the same survey, 13% of transgender Americans are unemployed, almost double the national average. 26% had lost their jobs due to their gender identity/expression. Transgender sex workers have high rates of HIV. In a review of studies on HIV prevalence in trans women working in the sex industry,
over 27% were HIV positive. However, the review found that trans women
engaged in sex work were not more likely than trans women not engaged in
sex work to be HIV positive.
Studies have found that in the United States HIV is especially prevalent
amongst transgender sex workers of color, particularly black trans
women, a problem that has been identified by academics and members of the transgender community.
The subject of transgender sex workers has attracted attention in the media. Paris Lees,
a British trans woman and journalist, wrote an article in June 2012 for
the Independent defending criticism of Ria, star of Channel 4
documentary Ria: Teen Transsexual, who was seventeen at the time
and depicted as working as a prostitute at a massage parlor, saying
that the choice to engage in sex work is a matter of bodily autonomy and
pointing out reasons that young trans women often turn to sex work such
as low self-esteem and severe employment discrimination.
A review by GLAAD
of its archives of transgender-inclusive television episodes from 2002
to 2012 found that 20% of transgender characters were depicted as sex
workers. A 2020 Netflix documentary, Disclosure, explores this in more depth.
History
Classifying transgender people by sexual orientation
Historically, transgender people were unable to access gender affirming care unless they would be considered heterosexual post surgery. For much of the early 1900s, transgender persons were conflated with being either an invert or homosexual; as such, non-heterosexual sexual orientation data for transgender people is limited. In the 1980s, Lou Sullivan was instrumental in allowing non-heterosexual transgender people access to surgical care and hormones.
Sexologist Magnus Hirschfeld first suggested a distinction based on sexual orientation in 1923.
A number of two-type taxonomies based on sexuality have subsequently
been proposed by clinicians, though some clinicians believe that other
factors are more clinically useful categories, or that two types are
insufficient. Some researchers have distinguished trans men attracted to women and trans men attracted to men.
In 1974, Person and Ovesey proposed dividing transsexual women
into "primary" and "secondary" transsexuals. They defined "primary
transsexuals" as asexual persons with little or no interest in partnered
sexual activity and with no history of sexual arousal to cross-dressing
or "cross-gender fantasy". They defined both homosexual and "transvestic" trans people to be "secondary transsexuals".
Dr Norman Fisk noted those entering his clinic seeking
reassignment surgery comprised a larger group than fit into the
classical transsexual diagnosis. The article notes that effeminate gay
men and heterosexual fetishistic transvestites desire surgery and could
be considered good candidates for it.
In the DSM-II, released in 1968, "transsexualism" was within the "paraphilias" category, and no other information was provided.
In the DSM-III-R,
released in 1987, the category of "gender identity disorder" was
created, and "transsexualism" was divided into "asexual", "homosexual",
"heterosexual" and "unspecified" sub-types.
In the DSM-IV-TR,
released in 2000, "transsexualism" was renamed "gender identity
disorder". Attraction specifications were to male, female, both, or
neither, with specific variations dependent on birth sex.
In the DSM-V,
released in 2013 and currently used in the United States and Canada,
"gender identity disorder" is now "gender dysphoria", and attraction
specifications are either gynephillic or androphillic.
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