One perspective regarding sexual desire and arousal states that any psychological changes correspond to changes in the brain. The sex hormones are released into the blood by glands and travel to the brain. Here, they sensitize particular regions. This makes these regions more responsive to sexual stimuli and thoughts. This implies that a biological event (e.g. loss of hormones) changes the activity of parts of the brain which is only experienced psychologically (e.g. loss of desire).

Psychological events can have effects throughout the body (e.g. anticipating a sexual encounter can increase levels of the hormone testosterone). A psychological change can precede biological changes. Events in the brain and mind are simultaneously biological and psychological.

Sexual transgression is often strongly socially disapproved and evokes blame. However, there may be a clear biological basis for this which needs to be taken into account without approving sexual transgression. Understanding the properties of the processes that help a person’s sense-making can give insight into how sexual desire, arousal and behaviour are organized.

Simple, self-regulation processes are built-in through evolution when there is a regular trigger to a straightforward action (e.g. reflex). This is because some reflexes may be inefficient if there was conscious control. However, novel problems require conscious processing and cannot be solved through reflexes.

Involuntary, unconscious processes exist alongside conscious processes that bring flexibility and creativity. These two types of processes integrate their control and behaviour is often based on a combination of them. There is behaviour that can be done automatically but also with full conscious control (e.g. brushing teeth0. The responsibility for a given task can move between automatic and controlled modes, depending on the circumstances.

In sexual desire and behaviour, learning plays a central role. Both classical and operant conditioning can play a role in learning of sexual desire and behaviour. A person’s awareness of the link between two events can influence the formation of an association between them (e.g. strengthening). Cues that have been paired with sexual activity acquire potency (incentive value) to trigger directed activity and searching (i.e. sexual arousal). For example, a person’s smell can be linked to attractiveness.

Dopamine systems are central to desires. There can be a strong craving and pleasure associated with its satiety in desires. Sex shares common features with feeding and drug/taking that the presence of the triggering stimulus causes the future to be devalued (e.g. hungry people prefer an immediate reward rather than a delayed bigger reward).

There are several commonalities between feeding and sex:

• It is both associated with pleasure.
• It is both influenced by variety.
• It is both influenced by labelling (e.g. salmon ice cream is not seen as positive whereas salmon fillet is).
• It can both serve goals simultaneously.

There are also several commonalities between drug-taking and sex:

• It both improves mental state (e.g. relief from anxiety).
• It can both be an acquired taste (i.e. initial experience not being great but a dependence upon context).
• A desire for both can be triggered by stress.
• A craving for both is situation-dependent.

Both gambling and sex are associated with uncertainty of outcomes and this is something people appear to like. Uncertainty and curiosity are important in sex and a lot of desires. The similarities in sex and other desires occur because of shared brain processes. The different desires that share commonalities with sex can interact (e.g. taking drugs to enhance sexual desire).

A functional explanation refers to an explanation in terms of how an aspect of behaviour helps an animal transmit its genes. It is not the same as a causal explanation. It is useful to know what something was designed to do. It appears as if sexual desire was designed by evolutionary processes to be part of the means to pass on genes (e.g. trigger mating). Fitness refers to a measure of the success shown in genetic perpetuation (e.g. leaving more offspring indicates a higher fitness). It is not the same as physical fitness.

An indiscriminate mating strategy refers to a desire for sexual variety and casual sex. This is the preferred strategy for men but not for women from an evolutionary perspective. This is not the preferred strategy for women because women have more to lose as a result of reproduction processes.

Evolutionary mismatch refers to the disparity between the current environment and that in which evolution occurred. Sexual desire evolved in a vastly different environment than the modern sexual environment. Attractiveness is artificially enhanced in modern society (e.g. dress; plastic surgery). Stimuli that were present in evolutionary history but are artificially changed to specifically match the evolutionary need in excess are supernormal stimuli (e.g. high fat, high sugary food).

The triggers to desire and the means to translate this into novel sexual behaviour are more accessible to most people than at any time in history before. This wide change in the sexual environment determines that sexual desire is more widely available for everyone.

The brain of animals makes use of a cost-benefit analysis. Today’s diseases were not present during most of human history and are thus not taken into account with evolution. In the context of high desire, a long-term theoretical risk (e.g. disease) may not outweigh short-term benefit (e.g. sex).