Having advanced the case for an incentive motivation model of sex, it is necessary to fit this idea to the notion of levels of organization, exemplified by automatic and controlled processing (Chapter 2).

Evidence points to behaviour being determined by at least two levels of control in the brain (Carver et al., 2009; LeDoux, 1999; Toates, 1998, 2006):

• an evolutionarily old low-level system, which is (‘automatically’) reactive to specific events in the world. It can sometimes operate at an unconscious level;

• an evolutionarily new high-level (‘controlled’) system that operates at a conscious level and seeks long-term rational goals (e.g. to maintain marital harmony, resist temptation).

The levels of organization can act in the same direction (e.g. both tending to trigger behaviour) or in opposition (e.g. low level excites behaviour, while high level tends to restrain).

Sexual desire probably does not usually exist in isolation, though for some people it might best be understood in these simplified terms. As a more general principle, sexual desire locks into interaction with other processes and only by looking at its interactions can it be understood. This chapter describes three such interactions.

Attachment, care-giving, love and romance

Sexual desire interacts with a motivation that is variously described as seeking ‘companionship’, ‘love’, ‘attachment’ or ‘romance’. Attachment is essential for some to express sexual desire, in which case sexual desire needs to be understood in terms of its links with this primary motivation. This is illustrated by a number of personal accounts, such as the following: The pop singer Madonna wrote (Madonna, 1992, p. 3): ‘Sex is not love. Love is not sex. But the best of both worlds is created when they come together.’ Meston and Buss (2009, p. 30) give the witness of a 25-year-old woman: ‘We were both sixteen-year-old virgins and had been dating for three months. I pushed for us to have sex because I wanted to show him that I loved him. I wanted to give him something that no one else could have.…I probably lost my virginity out of a need to be loved’, and ‘Sex to express love is about being able to put feelings into actions. With different kinds of love there are different ways to express that love through action. When I physically and/or mentally desire someone I may choose to show that desire through sexual actions.’

Is sexual desire part of a regulator?

Sexual desire and behaviour appear superficially to exhibit some features of regulation. However, as Chapter 3 indicated, there is little evidence to support any of the actual regulatory processes that have been postulated over the centuries and considerable evidence against them.

With little controversy, deprivation of sexual opportunity can be felt by some as aversive, while sexual outlet is felt as pleasurable and restorative. This much is in common with feeding and drinking, systems unambiguously concerned with regulation. Or, to take another analogy, there is at least something in common with a full bladder and the urge to urination. However, while acknowledging some level of similarity, one needs to look closer and ask – where lies the source of distress that comes from not being able to express sexual desire? Considering the similarities and differences with feeding and drinking can give useful pointers to the design of sexual desire (Singer and Toates, 1987).

Basic principles

As a general principle applicable across various sexual and non-sexual situations, a wide range of species, for example rats, monkeys and humans, show a preference for some novelty (Bardo et al., 1996). That is to say, the brain is particularly sensitive to change in what arrives at the sense organs relative to an unchanging pattern of stimulation. In experiments, animals work to achieve change in their physical environment, for example by pressing a lever to alter the illumination or gaining access to a visual image.

In various species, humans included, novelty can be a powerful stimulus to sexual desire and points to the role of the external incentive. Desire can be re-ignited in a so-called ‘sexually satiated’ animal, human or non-human, when a new partner appears (Schein and Hale, 1965). Arousal by novelty suggests that motivation arises from an interaction between an internal factor, now re-sensitized, and the incentive.

The phenomena to be explained

If psychotherapists and gossip columnists had been plying their trades at the time of St Augustine, some would surely have diagnosed ‘sexual addiction’. These days, when news breaks on a sex scandal involving a public figure, pundits are sought in an attempt to answer the question: ‘Why on earth take the risk, since surely he must have known of the potentially disastrous consequences?’ The cases of Bill Clinton and Tiger Woods come to mind. Television journalists, psychiatrists and psychologists argue for and against the validity of the term ‘sexual addiction’.

Alas, such discussions are likely to descend into semantic hair-splitting. Those interviewed often cannot even agree that sexual addiction exists as a useful diagnostic category, let alone whether a particular individual qualifies for the label. (For a criticism of the notion of ‘sexual addiction’, see Ley, 2012.)