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How Sexual Desire Works- The Enigmatic Urge

Page 5

by Frederick Toates


  Taking care with dichotomies

  A dichotomy pervades public discourse on minds, brains and behaviour. It is expressed in different but related ways, usually as ‘mind versus body’ or ‘psychology versus biology’ and has echoes of that between biology and social factors (Chapter 1). The dichotomy is exemplified by such claims as – ‘the problem is purely psychological’ or ‘could there be a biological reason for this?’ Such logic is fraught with hazards, leading to much confusion.

  Suppose that, as a treatment for cancer, a woman’s ovaries or adrenal glands are removed. This would cut off the supply of hormone secreted by the gland. Similarly, a man with prostate cancer might take medicine to lower the level of the hormone testosterone. Following these interventions, suppose that sexual desire falls. It would be correct to describe this as a biological cause of the loss of desire. However, to the individual concerned, sexual desire and its loss represent psychological phenomena. So, even though the initial cause can be described as ‘biological’, the effect of the hormonal change is experienced as psychological. So, how can a biological change have a psychological effect?

  According to the perspective advanced here, any psychological changes correspond to changes in the brain. Sex hormones are released into the blood by glands and travel to the brain, where they sensitize particular regions, making them more responsive to sexual stimuli and thoughts. Therefore, following a loss of hormones (a biological event), the activity of particular parts of the brain changes. This is simultaneously experienced as the psychological state of loss of desire. Restoration of the lost hormones would re-sensitize the brain regions and might well be experienced as a recovery of sexual desire.

  Reciprocally, events described as ‘psychological’ can have effects throughout the body. For example, a change of sexual partner can increase sexual motivation, with effects on the hormones of the body (Woodson, 2002). Anticipating a sexual encounter can increase levels of the hormone testosterone (Zillmann, 1984). Consider erectile dysfunction as a result of blockage of the blood vessels of the penis by fatty deposits, so blood cannot get in sufficient quantities into the penis. This is a biological change. Yet, suppose that it sets up a vicious circle with anxiety, which makes the problem still worse, a psychological change (Bancroft, 2009). Contrast this with a situation where there is an initial psychological cause of sexual dysfunction. Suppose that a man becomes unemployed and falls into depression, a psychological cause for a loss of desire. Yet this change in the man’s mind is accompanied by corresponding changes in his brain, biological changes. As a result of the lowered activity in particular brain regions, the secretion of testosterone lowers, which in turn sets up a vicious circle by lowering sexual desire still more.

  So, one can describe initial psychological or biological changes that trigger a sequence of events. However, events in the brain/mind are simultaneously biological and psychological. This has a powerful implication, described next.

  Responsibility and blame

  Attempts to explain an individual’s desire can trigger soul-searching moral issues. Sexual transgression, like little else, evokes blame and strong social disapproval. Even violence, as depicted in TV and movies, is not censored to the same extent. I have not heard of anyone being dismissed from work or getting a divorce on the grounds of surreptitious viewing of even extreme violence, and yet social and employment rules are often draconian where it concerns pornography.

  Belief in human rationality, where people freely and inscrutably decide their own actions and destiny, leads to the notion of personal responsibility and accountability (Bolles, 1975). The torments of hell were said to await the sinner who voluntarily opted for the wrong choices. Unsurprisingly, transgressors usually search for an escape clause. For example, the theologian Paul Tillich1 had a history of extramarital affairs (C. Wilson, 1988), his widow providing evidence (Tillich, 1973). C. Wilson (1988, p. 215) suggested:

  Is it not, for example, inevitable that a man who cannot keep his hands off his female students will emphasize human helplessness and man’s inability to resist sin?

  Understanding sexual desires and actions in terms of brains, their evolution and development might afford a mitigating circumstance, particularly since some behaviour that deviates from norms can be associated with particular unusual brain function (Raine, 2013). So, if it can be argued that deviant behaviour has a biological basis, people and indeed courts of law are more inclined to take a sympathetic view. Examples include unexpected desires that occasionally arise from brain damage, as in traumatic accidents or from Parkinson’s disease.

  Space precludes a discussion of these issues here. Suffice to note that authors on the topic of sexual violence frequently caution that to explain is not to excuse.

  Some basic psychology

  Principles of organization

  Throughout the brain/mind, some fundamental principles of organization can be identified; that is, the same basic ‘design’ is repeated.2 Our perception of the world, mental life and behaviour, sexual and non-sexual, are organized and controlled by some similar types of processes. Understanding their properties gives insight into how sexual desire, arousal and behaviour are organized.

  Consider the simplest case, a reflex, exemplified by the pupil of the eye widening on going into the dark and constricting in the light. This happens quickly and automatically, involving no intention or conscious awareness. A stimulus, a change in illumination, triggers it; the reflex is ‘stimulus-bound’. Similarly, the digestion of food and the beating of the heart are organized automatically; you do not decide consciously when to start or stop them. It is just as well; chaos would ensue if we had much voluntary control over the insides of our bodies.

  In evolution, relatively simple processes that are self-regulating have been selected where the solution can be built in and there is a regular trigger to a straightforward action. For example, there would be nothing to gain and much to lose by a facility for conscious intervention in the pupil light reflex. It would waste valuable brain capacity in solving a problem for which the solution can be built in. Similarly, the system that causes the withdrawal of a hand from a hot object is best done by an automatic and non-conscious reflex. In protecting the body, speed is of the essence and the stimulus of heat triggers action very rapidly. Imagine that you had to decide consciously and form an intention to pull the hand away. This would waste valuable time and risk serious injury.

  For many other tasks, it is impossible to produce a brain with the requisite solutions preformed and ready to go. So, what factors underlie whether automatic and non-conscious reflexes or full conscious control are responsible for a given bit of behaviour?

  Contrast such automatic reactions with those that require full conscious awareness. For example, imagine that you are lost in a strange environment. Full conscious awareness is brought to bear on trying to navigate your way. There is no stimulus to trigger automatic behaviour. Novel problems, such as this or how to negotiate a deal with a stranger, demand novel solutions and they cannot be built into the brain in advance. They involve assimilating information from past experiences, searching memory for relevant information and exploiting this information on the particular and often unique features of the current situation. They involve complex intentions, like what you hope to get out of any social negotiation.

  Involuntary unconscious processes exist alongside conscious processes that bring flexibility and creativity. Speech exemplifies this. Our utterances are novel in terms of the intentions underlying them and the meaning that we wish to convey. We often operate in full conscious control as we speak, responding flexibly moment by moment to the changing circumstances triggered by the interaction with our interlocutor. Nonetheless at another level speech depends upon being able to call upon a bank of preformed expressions, some clichés, which run off in a more automatic mode, triggered by appropriate turns of the conversation. The two types of process integrate their control and often a given instance of behaviour is based upon
a combination of them.

  Some behaviour can be done either with full conscious awareness or automatically. For example, many people brush their teeth while on ‘autopilot’, by repeating the same sequence of movements every day. Yet this task can be done with full conscious awareness directed to it, as recommended by dentists and mindfulness meditation gurus alike.

  Reflecting these considerations, a fundamental distinction in the way that behaviour is organized by the brain, including sexuality, is between what are termed automatic and controlled processing.

  Automatic and controlled processing

  Imagine walking down a sloping pavement, while your conscious mind is fully engaged in conversation. You pay no attention to what your legs are doing, even though walking is a skilled activity involving complex calculations by the brain. The walking part of your behaviour is on ‘automatic’ control, acting in a non-conscious mode. This frees those parts of your brain that are running in the conscious or ‘controlled’ mode to deal with the conversation, to interpret the meaning of the words that you are hearing and articulate your reply.

  Now imagine the same situation but this time there is ice under foot and you start to slip. You would instantly stop the conversation and bring full controlled conscious processing to bear on the task of staying upright. Your conscious controls would be engaged with looking for possible supports such as a handrail and selecting parts of the path that appear to be ice-free. In other words, according to circumstances, responsibility for a given task can move between automatic and controlled modes.

  Learning

  Learning plays a central role in sexual desire and behaviour. There are a few terms associated with learning that require some explanation.

  The expression ‘habituation’ refers to a decline in the intensity of a reaction after repeated exposure to a particular stimulus when there is no important consequence. An example is our tendency to ignore the harmless ticking of a clock after repeated exposure.

  The term ‘reward’ refers to those things with which an animal, human or otherwise, strives to maintain contact and which are assumed to have a pleasant effect. Food, water and sexual contact are described as ‘rewards’. The expression ‘incentive’ has some similarities in meaning but with an emphasis upon the reward’s power to attract the animal towards it. For example, a location in the past associated with mating to which an animal is drawn would be described as an ‘incentive’.

  There are different types of learning, some common across species and some that appear to be particularly human. In the first category, classical and instrumental conditioning are found.

  Classical conditioning is exemplified by Pavlov’s experiment on salivation in dogs, triggered by food (Figure 2.1a). A tone with no capacity to trigger salivation was sounded immediately prior to giving food. After a few joint presentations of tone and food, the tone acquired the capacity to trigger salivation. The tone became a ‘conditional stimulus’ to salivation. The term ‘conditional’ is used, since the condition for the tone to have such a capacity is its pairing with food. This much is common across species, but in humans conscious awareness of the link between the two events can play a role in forming an association between them.

  Figure 2.1 Classical conditioning: (a) salivation (i) prior to pairing, (ii) pairing and (iii) following pairing; (b) sexual arousal

  Classical conditioning features extensively in discussions of sexuality (Bancroft, 2009; Pfaus et al., 2013). Across species, cues that have been paired with sexual activity acquire potency (‘incentive value’) to trigger directed activity and searching (‘sexual arousal’). The importance of this in nature is easy to appreciate. Suppose a particular odour has been paired with a sexual stimulus. This odour can label a partner or location as sexually desirable, so that in future the animal is motivated to pursue the odour. In humans, a range of different otherwise neutral events can become associated with sexual arousal, for example by chance pairing (Figure 2.1b). This is particularly evident in the case of men and it probably contributes to the surprisingly wide spectrum of desires that they exhibit.

  Instrumental conditioning is where the consequences of behaviour change the future probability of showing that behaviour (Figure 2.2), and is exemplified by the maze. Typically, a hungry rat learns to navigate a maze since it obtains the reward of food at the end. The chances of taking the correct turns increase as a result of the reward. Another form of instrumental conditioning is termed ‘operant conditioning’ and is exemplified by the Skinner box. A hungry rat learns to press the lever in the box since the lever-press is followed by, say, the presentation of food.

  Figure 2.2 Instrumental conditioning

  Food is said to reinforce the behaviour of lever-pressing, meaning that the future behavioural tendency to press is strengthened by the food. Food is an example of positive reinforcement since the reinforcing event is presented as a result of behaviour. There is also ‘negative reinforcement’, where the strengthening occurs as a result of the removal of something as a result of behaviour. This is exemplified by the termination of a loud sound by an action. Orgasm exemplifies positive reinforcement, while an escape from, say, boredom by means of sexual behaviour exemplifies negative reinforcement.

  In addition to such conditioning, people form peculiarly human cognitions about the social world, such as gender identity based upon their observation of gender differences (Bancroft, 2009). Bodily and psychological changes at puberty are assimilated into the growing child’s identity, which leads logically to a consideration of biology.

  Some details of the relevant biology

  The psychological phenomenon of desire, its loss and restraint can be linked to underlying processes in the brain. Parts of the brain that are active at times of sexual desire can be identified by neuroimaging and hence some brain correlates of desire found. Changes in desire and its expression or inhibition following damage to identified brain regions can be studied. Evidence derived from non-human species can be cautiously extrapolated to humans. To do this, the means of communication and control of the body need to be examined.

  Neurons and hormones

  Neurons are a particular class of cell found in the brain and throughout the body (Figure 2.3). The nervous system consists of all the neurons (and some closely associated cells) of the body (Figure 2.4). There are billions of neurons and they transmit and process information. The activity of particular combinations of neurons in the brain is the basis of our thoughts, perceptions and desires. One circuit of interacting neurons would form the basis of, say, sexual desire and a different circuit might underlie orgasm. Investigators try to find the location of such circuits in the brain and define the pathways of neurons that form them.

  Figure 2.3 Neurons: (a) individual neuron; (b) neurons forming systems

  Figure 2.4 The nervous system comprises the central nervous system (CNS) and the peripheral nervous system

  Neurons also transmit information from one bodily region to another. For example, when a region of the body is stimulated by touch, a message is sent to the brain in the form of electrical activity (‘action potentials’) in neurons that form a pathway to the brain. In the brain, the message is interpreted in terms of the touch’s location, intensity and any emotional significance.

  When neurons are electrically active, that is processing information, they require a source of nutrients and oxygen brought by the blood. The more active they are, the greater is the demand for fuels. The technique of functional neuroimaging exploits this fact in order to observe which bits of the brain are most or least active under different conditions, such as viewing erotic pictures as compared to neutral pictures.

  Neurons communicate with each other at junctions, known as synapses (Figure 2.5a). Typically, one neuron (A) contains a chemical substance, known as a neurochemical (in many cases, more specifically a ‘neurotransmitter’), at its terminal. When the electrical signal arrives at the terminal, it causes the release of this neurochemical into the gap an
d the occupation of receptors on neuron B. This then affects the activity of B. The neurochemical can excite further electrical activity in B (Figure 2.5b) or it might inhibit activity in B (Figure 2.5c). A number of such neurochemicals are involved in sexual desire and behaviour. The best known are probably dopamine, serotonin and a class known as opioids.

  Figure 2.5 Synapse between neurons: (a) synapse; (b) one neuron excites another; (c) one neuron inhibits another

  Drugs such as cocaine and heroin powerfully alter the activity of particular classes of synapse in the brain and thereby mimic effects that would under more natural conditions be brought about by, say, sexual events. They target synapses in brain regions normally involved in conventional wanting and liking, and thereby offer powerful interactions with natural activities such as sex.

  Another means of communication is by hormones. These are chemicals that are secreted (often from a gland) into a blood vessel and transported by the blood from a site of release to a site of action (Figure 2.6). The hormones of most interest here are:

  The class termed ‘androgens’, that of prime concern being testosterone. They are secreted from the testes in men, the ovaries in women and the adrenal gland in both sexes.

 

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