How Sexual Desire Works- The Enigmatic Urge

by Frederick Toates

  One benefit in investigating, say, feeding or gambling is that they are relatively easy to study under semi-natural (‘ecologically valid’) conditions. The gambler and a casino or the eater and a mini-cafeteria can be brought into the laboratory to study. The person addicted to nicotine or alcohol can be observed as they engage in their behaviour or try to resist it. They can be offered their favourite substance in the laboratory or asked to work to obtain it and the reaction observed. For rather obvious reasons, it is well nigh impossible to follow, say, the lecher on his adventures under anything like ecologically valid conditions or to bring sexual uncertainty and variety into the laboratory and observe their role in triggering desire.

  Sex shares the common feature with feeding and drug-taking that the presence of the triggering stimulus causes the future to be devalued (‘discounted’) (van den Bergh et al., 2008). Hungry people prefer a small immediate food reward rather than a delayed bigger reward. People addicted to heroin or nicotine show a preference for an immediate reward of a small amount of drug, as opposed to a later larger amount of drug. The personal assessed risk of getting a sexually transmitted disease is lowered by showing men sexually attractive images or asking them to do the assessment during masturbation (Ariely and Loewenstein, 2006).

  Comparison with feeding and drinking

  Feeding and drinking maintain chemical and energy levels within the body. Without force-feeding, death will obviously follow loss of desire for food. On some occasions, people do abstain from feeding, as in hunger strikes or anorexia nervosa. The consequences are, of course, ultimately lethal and surely this is not a life-choice willingly and happily sought. In this regard, sex appears very different. However, the fact that the consequences of being without something are different should not detract from some similarities in how sex, feeding and drinking work.

  Like sex, both feeding and drinking are also associated with strong desires, and particularly in the case of feeding with considerable variation between individuals in the intensity with which it is expressed in behaviour. Feeding and drinking are associated with pleasures, sometimes intense, that encourage us to repeat the activities, particularly when in a bodily state of deficiency. Given the opportunity, variety plays a dominant role in the desire for food, as is evident by the marketing strategies of supermarkets or the range of ethnicities of restaurants in any town centre. Who has not found their appetite suddenly revived when a new course is presented? For both feeding and sex, some people are better at restraint in the face of plenty and variety than are others. Stress can trigger ‘comfort eating’, something similar being found for sex. Certain foods appear to lift mood, as is the case for sex (Meston and Buss, 2009).

  As with sex, humans put tastes into a complex context by labelling their meaning, involving the prefrontal cortex (Rolls, 2012). For example, smoked-salmon ice cream has almost no pleasantness rating when it is called ‘ice cream’. However, a label of ‘savoury mousse’ or something quite arbitrary such as ‘food 386’ gives it a strong positive hedonic value (Yeomans et al., 2008). I will leave it to the reader’s imagination to find examples where the way in which something sexual is construed makes all the difference to its hedonic value.

  Feeding, like sex, can serve several goals simultaneously. A person might eat with little thought of anything but correcting hunger. On another occasion, nutrient regulation might play less of a role; eating in a restaurant might involve stimulating conversation, passing time and creating the right impression. More food is eaten by people in company than eating alone (Wansink, 2006).

  Comparison with drug-taking

  Drugs improve mental states, offering temporary relief from anxiety, stress or a depressed mood, as does sex (Meston and Buss, 2009). They are associated with a ‘high’, which has been compared to orgasm, the culmination of first obtaining and then taking them.

  Despite being in an environment where there is peer pressure to take drugs, some people shun them entirely. Some take them in moderation and as part of a healthy life-style without getting addicted. Others get addicted to either drugs or sex or both simultaneously. Following addiction to drugs, people can risk life, limb and liberty to get them. In the absence of their drug, they might feel withdrawal symptoms and crave drugs, a similar experience to some deprived of sex. Craving (intense wanting) seems to be a common feature of desires (Kavanagh et al., 2005). Stress can trigger a desire for drugs as it can for sex (Chapters 15 and 17). A craving for drugs can be situation-dependent; an environment that in the past was associated with taking drugs can trigger craving because of the cues present (Robinson and Berridge, 1993). Similarly, potent cues such as a region of town associated with past sexual encounters or the keyboard on a computer used for viewing pornography can trigger sexual urges.

  Some addicted people can quit even hard drugs for life (Heyman, 2013), as do some people manage to quit sex. Drugs can be something of an acquired taste (Alexander, 2008; Robinson and Berridge, 1993), as can sex (Levin, 2006), with initial experiences not being that great and a dependence upon context.

  Such drugs were surely not an integral part of our evolution and neither are we naturally equipped with brain processes that lead us to seek them out. Rather, they appear to hijack brain processes that evolved to serve such normal desires as for food and sex (Nesse and Berridge, 1997), most clearly those involving dopamine (Figure 2.10). However, a study of this hijacking can in itself reveal much about the particular brain processes that are hijacked and which normally serve conventional activities such as sex and feeding.

  Comparison with shopping

  Some purchases are made impulsively, apparently serving psychological needs of comfort, improving self-image and status, rather than being based on rational and purposive choice (Dittmar and Drury, 2000; Rook, 1987). This can get out of control and lead to a full-blown addiction (O’Guinn and Faber, 1989). The perception of the object itself creates a powerful desire for it, a principle that applies to such things as clothes and jewellery rather than to toilet paper or lettuce. Stress tends to increase the desire for impulsive shopping. Behaviour is not simply a response to being by chance in a shopping situation. Rather, the memories are such as to lead people to make an effort to move towards shops. Shopping stampedes can prove lethal.

  Many left-at-home partners can surely observe with only thinly disguised envy the ability of advertisers to create inordinate levels of wanting. Uncertainty over what might be the next bargain seems inherent to the attraction. However, the large number of household gadgets gathering dust, unworn clothes, unread books and little-played CDs seem to point to a rather lower intensity of liking.

  Comparison with gambling

  Gambling, with its associated risk of addiction, has features in common with what some people find attractive about sex: uncertainty of outcome, high arousal and the potential for big rewards. The gambler never knows what is going to happen next and how big the winnings, if any, will be. The gambler’s heart rate accelerates while engaging in the activity. Anticipation of winning triggers some of the same brain regions as are excited when a drug-user anticipates getting a shot of drug (Breiter et al., 2001). Some people spend enormous amounts of time and money gambling, occasionally losing their last dime, their family and even their lives in suicide as a result. Some are lured to Las Vegas from thousands of miles away, by the promise of uncertain reward, somewhat comparable to the behaviour of sex tourists.

  The casino is rich in stimulation, gaming machines, music and lights, associated with occasional and unpredictable winnings. Internet gambling captures some of this in an even more accessible way. One feature shared between contemporary gambling and the environment in which humans evolved is surely the uncertainty of gain. The individual who persisted in the pursuit of goals, for example food, mates, shelter, in the face of such uncertainty might have been at an advantage in terms of genetic perpetuation. Risk-taking within limits could well have been an adaptive trait in our early evolution, allowing colonization of n
ew habitats and finding new mates and so on.

  Comparison with other recreational activities

  Finally, consider curiosity and exploration of the environment and how this compares with sex. For some, a holiday is a waste of time that would be better spent at work. For others, a regular annual holiday by the seaside with nothing much going on is perfectly adequate to satisfy their limited curiosity about the world. Still others pay large sums and incur enormous inconvenience and danger to visit remote parts of the world. Some travel the world to follow their favourite football team.

  Why do some people opt to cross deserts, explore jungles and climb Everest? Why do others play chess, do crossword puzzles or frighten themselves by watching horror movies? Surely, seeking uncertainty, arousal and novelty and then trying to ‘resolve’ it is a fundamental feature of the human condition. There is satisfaction in, for example, bringing the order of a solution to a crossword puzzle. To Gopnik (1998), the similarities between curiosity and sex are so striking that she entitled an article ‘Explanation as orgasm’. We are moved to understand chosen parts of the world and when we find an explanation, as in the missing answer to a crossword, there is a sudden burst of pleasure that motivates us to repeat the experience.

  There is suspense in the chess game or football match, resolved by the outcome. The tension of a crime novel or horror movie such as Psycho is resolved with the denouement. The exotic island gives up its mystery as it becomes slightly familiar. The uncertainty, suspense and eager anticipation of the football match is relieved by a winning goal and particularly by ending the match with one. A group of England football supporters on their way to an international competition once described to me the similarities with sex, adding that a winning goal was even better than orgasm. This might come as little surprise to some stay-at-home wives. In spite of the similarities, it is probably best not to mention a comparison with watching football, and even more so with horror movies, too soon after the start of a new erotic liaison.

  Think of the angler sitting for hours in all weathers waiting for the perfect catch. This behaviour seems motivated by the uncertainty of when the catch will happen and its form. This is resolved once the line is tugged. To catch a visible fish from a small tank, though more certain, would presumably be less appealing. Is this experience of waiting and suspense not similar to that felt by the voyeur sitting for hours in the bushes waiting for the perfect image of a woman undressing, or the exhibitionist investing hours in finding the optimal location for exposure?

  Advantages of a broad approach

  Quite apart from the relative ease of doing research in areas other than sex, there are good reasons to consider sex in the context of activities such as taking drugs, curiosity, feeding and drinking. First, as just noted, there are similarities between them. Indeed, I will suggest that this arises since they share some common brain processes that involve dopamine and other chemicals. Of course, there are also differences in these activities and investigating these can also enhance our understanding.

  Secondly, these activities can interact (Chapter 15). Often drugs are taken to enhance sexual desire, while the urgings of curiosity are sometimes given as a motivation for sexual exploration. A number of women report that they initiated sex out of the simple curiosity that they ‘wanted to see what all the fuss was about’ (Meston and Buss, 2009). In one sample, curiosity topped the list of reasons for loss of virginity (Shope, 1971). Gambling and sex sometimes go together (Chapter 17).

  The brains that we study in the here and now are the product of evolution and individual development, and considering these aspects reveals much about sexual desire, to which the discussion turns next.

  Evolutionary perspectives

  Basics

  It is widely agreed that humans are the product of a process of evolution taking place over millions of years. In sexual reproduction as exemplified by humans, genes from male and female are combined at the time of fertilization. The combination of genes, termed the ‘genotype’, is then locked into dynamic interaction with, first, the environment of the fertilized cell, the womb and then the external environment, with its physical and social aspects. The animal is placed in a competition for survival and reproduction. Some animals are more successful than others and thereby their genes tend to get transmitted to future generations. Over many generations, evolution occurs such that the animal is said to be adapted to its environment.

  There is some new terminology to introduce in the context of evolution. A ‘functional explanation’ is one in terms of how an aspect of behaviour helps an animal to transmit its genes. It asks what is the function of any instance of behaviour and stands in distinction to the ‘causal explanation’, discussed earlier. Causal and functional can ideally be fitted to give a more comprehensive understanding. For example, consider that an animal can often be sexually re-aroused by a change of partner (Chapter 11). A causal explanation for this would be in terms of events within its brain, specifically activity in pathways using dopamine. A functional explanation would be in terms of spreading the animal’s genes more widely. Of course, no one is suggesting that the animal has any conscious intention to spread its genes. It is simply assumed that those animals showing this effect left more descendants than those not showing it and hence the genes having such an effect have been more successful in propagation. Another term employed here is ‘fitness’. This is a measure of the success shown in genetic perpetuation. Animal A shows greater fitness than B if A leaves more viable offspring than B. Fitness used in this sense is not to be confused with the narrow sense of physical fitness, though doubtless physical fitness contributes to fitness used in the broader sense.

  Considerations of function lead to the notion of ‘parental investment’ (Trivers, 1972). This term refers to the cost in evolutionary terms of producing offspring. For a woman, the cost is much greater than for a man, since her reproductive system is out of action for more than nine months. She needs to supply nutrients to the growing foetus as well as incur an increase in weight. The cost is measured against what she might be doing if not producing this offspring (Gangestad and Simpson, 2000). By contrast, the investment of the male might be as little as the time spent in mating. From these considerations it is argued that women should be relatively more cautious and discriminating about engaging in sex.

  Evolutionary psychology is the study of psychology from the perspective of evolution and adaptation. It asks how the characteristics that are evident today served an adaptive function in our early evolution. Evolutionary psychology has had much to say about human sexuality (Workman and Reader, 2014), an approach that has yielded some profound insights.

  Evolutionary psychology and the notion of ‘design’

  One way of asking ‘how does sexual desire work?’ is to pose a closely related question – ‘how was it “designed”?’ I put ‘designed’ in inverted commas to indicate the sense of metaphor as it is employed by evolutionary psychologists. That is to say, brains that form the basis of sexual desire have presumably been ‘designed’ by evolutionary processes, since such desire was part of the means for passing on genes. Evolutionary psychologists frequently use ‘design’ by analogy with design in technology. In trying to understand how, say, a television or computer works, it is useful to know something about what it was designed to do. Evolutionary psychologists suggest that it is as if brains were designed and they ask what each feature of brain and behaviour was designed to achieve.

  Evolutionary psychologists describe their endeavour as ‘reverse engineering’. An engineer designs something either from scratch or by modifying an existing design. By contrast, the end product, the human, has already been ‘designed’, so the task is to speculate on what functional considerations were involved in this construction.

  The design was made way back in our evolutionary history and the environment has changed massively since then. The primary concern here will be how does this pre-stone-age design trigger desire in the twenty-first century? W
e ask how the brain that emerges is able to produce behaviour, ranging from sexual disgust and celibacy through blissful fidelity and monogamy to agonizing temptation, death-defying sexual risk-taking, extremes of promiscuity and sexual addiction.

  It is as if desire was ‘designed’ by evolutionary processes to trigger mating and thereby the production of offspring. However, the issue is more subtle and nuanced, since desire fluctuates. It is turned on and off, expressed or inhibited, according to various internal and external conditions. The design metaphor is useful in understanding how and why these conditions exert their effect. This can be interpreted in terms of the role that fluctuations in desire served in maximizing the chances of successful reproduction in our early environment (Workman and Reader, 2014).

  A principal area of interest is differences between the sexes in terms of the desire for sexual variety, casual and indiscriminate sexual behaviour and viewing pornography. In general, women appear less attracted than are men to these aspects of sexuality. Evolutionary psychologists suggest that this difference in sexual strategy reflects a difference in what was optimal for spreading genes. According to this perspective, women have more to lose by an indiscriminate mating strategy, whereas men have relatively little to lose and much to gain.

  Evolutionary accounts also ask the question of when in evolution a particular characteristic appeared, for example, the link between sexual behaviour and forming pair-bonds. Not all species show pair-bonding; some of our close ape relatives do not. So, under what circumstances did pair-bonding appear in evolution and what are the implications for sexual desire?