Motivation and emotion/Book/2016/Sexual motivation and hormones

Overview
For all animals, excluding human and dolphins sex is exclusively about reproduction and survival. For humans however, studies have shown that men and women are now investing the time and emotions to dissociate sexual behaviour from just reproduction (Zetterberg, 1969). The Swedish study states that there is one fertilisation per 1100 copulations, illustrating that our attempt to do more than reproduce is quite successful. Sex is a part of being human, but what motivates us to partake or not partake.

Is it a basic instinct driven by hormones and our need to survive? Obviously the answer is no, so if there’s more to it. What are our motivations to have sex?

''Ever wonder what drives people to have sex?  Is it emotional or just physical? ''

''Is motivation for sex different for men and women? ''

''What role do hormones play in motivating us to have sex? ''

These are just some of the questions that will be answered in this chapter.

By studying the relationship between sexual motivation and hormones we can help distinguish what makes humans different from other organisms, sexually.

Definitions
Sex: the most general definition for sex is, however, not limited to penile-vaginal intercourse. Other forms of intimacy considered to be sex are anal and oral sex (Peterson & Muehlenhard, 2007)

Hormones: are special chemicals created by the endocrine glands that control bodily functions (Hormone Health, 2016)

Sexual motivation: Motivations can be defined as being an increased state of interest in a particular goal. In regards to sexual motivation, the goal is to experience the physical and emotional satisfaction associated with sexual behaviours (Hill & Prestion, 1996).

Sexual desire: Is a subjective feeling, caused by internal and external factors. This may or may not result in overt sexual behaviours (Beck et al., 1991)

Testosterone


In males, gonadal steroids are bound to specific receptors in several areas of the brain, including the preoptic area (MPOA). When gonadal steroids are implanted in the MPOA of male rats, sexual behaviour is activated. Moreover, when lesions are made in MPOA it has been found to eliminate sexual behaviour in the male rat (Agmo, 1999). This suggests that hormones interact with the brain to produce a desire for sex.

Testosterone is one the most important androgens (male sex hormone) that is responsible for male development throughout puberty, without it they would never develop into sexually mature adults who can reproduce. It is responsible for physical growth, such as the development of the penis and testes, however, can also act on cells in the testes to make sperm. Testosterone is predominantly made in the testes; however, a small amount also forms in the adrenal glands. The pituitary gland and the hypothalamus control the production of androgens and sperm (Andrology Australia, 2016).

Gerianne, Packard & Hines (1994) found that testosterone (TST) enhances some aspects of sexual motivation. They hypothesised that there is an increase in plasma TST, this occurs by facilitating expression of learned associations between environmental stimuli and sexual activity. However, because males have higher levels of TST, then their theory only applies to males. To put in simpler term, when males are in an environment where they have previously engaged in sexual activity before (i.e., the bedroom) a rise in plasma TST results which in turn, increases sexual motivation. Udry, Billy, Morris, Groff & Raj (1985), study on adolescent male, investigated what was more influential on sexual motivation – they compared social factors and hormones, more specifically TST. They found that TST on its own was a strong motivator for sex, however social settings and social growth also had an impact on sexual motivation.

It is obvious for TST to have an effect on male sexual motivation, but what about female sexual motivation? Sherwin, Gelfand & Brender (1985) plasma TST had a clear effect and enhanced intensity of sexual motivation. Increased arousal and frequency of sexual fantasies were observed in the subject group. Moreover, it was found that TST did not affect the physiological response once sexual activity was obtained. Suggesting that the impact of TST in women was only on sexual motivation and not sexual activity. (Rako, 1999) showed a relationship between increased testosterone in women and increase risk taking behaviour. To extent, the research could predict that a correlation between increased risk taking behaviour and increased sexual activity.

Oestrogen (Oestradiol)


Oestrogen is the major sex hormone in the female body, Oestradiol is one of the three oestrogens. Oestradiol is the primarily the strongest of all three in the reproductive system. Its main function is to mature and maintain the female reproductive system. During menstruation, it is the increase in oestradiol level that is responsible for the maturation and release of the egg; moreover, the thickening of the uterus lining which allows the egg once fertilized to implant and begin to grow (Hormone Health, 2016). Grammer, Renninger and Fischer (2004) believe that female sexual motivation is at its highest around the time of ovulation. Due to the fact that oestradiol is responsible for ovulation and relationship can be noted between the two. It makes sense evolutionally that females are motivated to have sex around this time because there is more chance to get pregnant. However, too much oestradiol in women has been linked with low sex drive, young girls may see delayed puberty with low levels of oestradiol which can affect sexual motivation (Hormone Health, 2016).

While in men, it has no link to sex drive but helps with bone maintenance, nitric oxide production and brain function (Hormone Health, 2016).

Progesterone & Oxytocin


Progesterone is the hormone in women that is responsible for regulating important functions, playing a major role in maintaining pregnancy, preparing the body for conception and regulating the females monthly menstrual cycle. Progesterone is usually produced in the ovaries and by the adrenal glands, moreover, when a woman is pregnant it is also produced in the placenta (National Women's Health Resource Center, 2016).



For women, oxytocin is one of the most important hormones during pregnancy and more specifically birth. It controls signalling for contractions to begin and continue in the womb during labour. After birth oxytocin promotes lactation by moving the milk to breast (National Women's Health Resource Center, 2016). A study by Carter (1992) showed a linked between the release of oxytocin and behavioural effects during sexual motivation, orgasm, sexual satiety and other sociosexual interactions.

For men, oxytocin is less important. It has a role on moving of sperm and can also affect the production of TST in the testes. For both men and women, however, it has been found to play a role in recognition, sexual motivation, trust and anxiety (National Women's Health Resource Center, 2016). In regards to sexual motivation, increased oxytocin will often lead to heightened sexual motivation.

Although maintaining the body through pregnancy, these oestrogen, progesterone and oxytocin also play an important role in motivating women to get pregnant. Ovarian hormones have been found to have an influence on sexual desire, however, it is widely accepted that sexual behaviours are engaged in by females by perceived pregnancy risk (what are the chances that the female will end up pregnant if participating in sexual behaviours) (Wallen, 2001). Wallen (2001) believes, however, that female sexual motivation stems more from the cognitive stimulation than the hormones, unlike men.

Theories of Sexual Motivation
Sexual Response Cycle

Traditional (Triphasic)

The sexual response (pleasure) cycle was developed in later 1950s – early 1960s by William Masters and Virginia Johnson. The cycle describes men’s sexual motivation well, the model states that sexual desire is a result of arousal. (Masters & Johnson, 1966). The cycle defines the core components of sexual behaviour, and is not only applicable for humans but other species. It consists of 4 phases:



1.	Initial excitement: can be triggered by either biological or psychological cue which usually leads to stimulation of the genitalia area and the consummation of the sexual need

2.	Plateau phase: excitement and higher arousal, arousal may plateau during this phase but is usually relatively high

3.	Orgasm: climaxing with either ejaculation and/or orgasm. It should be noted that this stage is not always met.

4.	Resolution phase: breathing and heart rate return to resting rates. Males will experience a phase of satiety or transient sexual quiescence before sexual responsivity is regained. Also known as the refractory period. Women do not experience this phase.

(Georgiadis & Kringelbach, 2012)

Although the model is a coherent representation of sexual behaviour, it may not capture the variety of sexual response’s that occur during sex, especially during the orgasm phase and for women. In men, the correlation between the physiological and psychological arousal is high. Meaning that men sexual motivation is derived from physiological and psychological arousal, for example, sexual thoughts, fantasies, or genitalia stimulation. The model is a simple representation of the sexual behaviour, which aims to generalise the cycle of sex. But of course, sex is different for everyone so this needs to be taken into account. (Reeve, 2009)

In order to explain female sexual motivation, an alternative sexual response cycle was developed.

Alternative

The alternative sexual response cycle was developed to show that sexual motivation is not only a result of increase arousal but also an increase of willingness to receive or provide further intimate stimulation (Reeve, 2009). For women the correlation between physiological and psychological motivation is low. Unlike men, women’s sexual desire is usually not hormonal or arousal focused. Women’s sexual desire is focused around relationship factors, such as sharing emotional intimacy (text book). For women, emotional intimacy can be the difference of reaching the orgasm phase of the model or remaining in the arousal phase. It is not until the 3rd phase that physiological and psychological influences sexual motivation.

The model consists of 6 phases, but unlike the traditional model, it is a continuous cycle.



The phases are:

1.	Emotional intimacy 2.	Sexual neutrality 3.	Sexual stimuli 4.	Sexual arousal 5.	Sexual desire & arousal

Sexual motivation is increased as it also facilitates mental processing of additional stimuli towards further arousal. Sexual activities that women would not usually partake in, can be acceptable and highly arousing once emotional intimacy has been established. The model suggests that women become most sexually motivated when a highly emotional relationship is formed and begins in a non-sexual state of mind.

Further Theories
Beach (1956), was one of the first behaviourist to systematically analyse sexual motivation. His study aimed to make a basic distinction between sex and other spontaneous behaviours, such as eating and drinking. It becomes life threatening if we are without food or water a prolonged time, whereas there are no detrimental or life threatening effects if we are without sex. Moreover, deprivation can be easily expressed for food or water (e.g. numbers of hours since our last meal or drink), whereas deprivation of sex is subjective to the individual. In short, sex is not a physiological need unlike food or water – contrary to what many think. In aim to describe the underlying activation or motivation of sexual behaviour, Beach came up with the idea of ‘the sexual arousal mechanism’ (SAM), where its function is to increase male’s sexual arousal to a point where copulatory threshold is attained. He also described the underlying motivators of copulatory acts ‘the intromission and ejaculatory mechanism’ (IEM) – which will eventually bring the male to the ejaculatory threshold.

Hardy (1964) also made an attempt to describe sexual motivation. Hardy linked sexual motivation with incentive motivation. According to Hardy’s theory, mild local stimulation of the genitals as well as the orgasm are significantly pleasurable. The positive feelings that are associated with these events will promote sexual motivation in the future. The process was perceived to be independent from physiological factors including hormones such as androgens, progesterone and estrogen. The study added onto Beach’s previous research.

Sex as an Incentive



Hill and Preston (1996) propose that sexual motivation primarily involves the interest of attaining a general class of incentives, which provide a general type of satisfaction. This class is made up of a number of separate, but related incentives. Furthermore, their research suggest that our level of satisfaction is determined by our level on focus on the activity.

Proposed by Agmo (1999), sexual motivation is activated by stimuli, which can be divided into two classes, hedonically potent and hedonically neutral. The first class has two levels, hedonically positive or negative with hedonically positive stimuli more commonly known as positive incentives. Furthermore, a motivation aroused by this type of stimuli is named incentive motivation.

According to Agmo (1999) when a mate is perceived, for example, it acts as a stimulus and it’s supposed to active approach behaviour, which in turn acts an incentive. For this to be true however, the stimuli with sexual meaning has to be able to activate approach behaviour.

One of the first studies to identify sex as an incentive was conducted by Moss. He showed that males rates were willing to cross an electrified grid in order to engage in copulation with a female rat. The female rat functioned as an incentive, producing the powerful approach behaviour by the male rat. (Agmo, 1999). According to the model, sexual motivation is activated by incentive stimuli, usually in a particular order. Approach to an incentive (an environment where sexual activity has previously occurred, e.g. the bedroom), the appearance and reciprocal approach by another incentive (e.g. the female) until copulatory reflexes take over (Agmo, 1999).

Sexual Motivation for People in Relationships

Contingencies of Self-Worth Theory suggest that our motives are shaped by domains on which self-esteem are based, rather than the level of self-esteem (Crocker & Park, 2004). Relationship contingent self-worth base their self-esteem on their ability to maintain their romantic relationships (Knee, Canevello & Bush, 2008; Sanches & Kwang, 2007).

Relationship contingent self-worth is suggested to lead to greater sexual motivation aimed to maintain or enhance the relationship with their partners (relational sex motives). Sanchez, Moss-Racusin, Phelan & Crocker (2011) suggest that sexual motivations that focus on just maintaining a relationship may result in divergent sexual satisfaction. If the desire stems from the need for our partner’s approval or whether it’s from a desire to enhance intimacy motivation to engage will be affected. Sanchez, Moss-Racusin, Phelan & Crocker (2011) study focused on two theories of sexual motivation, they believe that our behaviours are driven by the pursuit of pleasurable outcomes (appetitive behaviours) or the avoidance of negative outcome (aversively motivated behaviours). In relation to relationship contingent self-worth, relational motives could potentially involve the desire to create positive outcome within the relationship, for example intimacy and closeness. Alternatively, we have a desire to avoid negative outcomes, such as disapproval from one’s partner. In short, people who base their self-worth on their intimate relationships, are more likely to be motivated to create positive relationships and avoid negative relationships to improve their self-worth.

However, the consequence of relational sex motives may result in a positive or negative experience for the person, depending on whether they are doing it to increase intimacy or avoid negative outcomes.

People who are motivated to engage in sexual activity with their partner just to seek their partner’s approval are likely to feel less sexually autonomous. This often leads to unwanted sexual behaviours, lower psychological well-being and decreased relationship satisfaction over time (Cooper, Shapiro & Powers, 1998; Impett, Gable & Peplau, (2005). In contrast, when a woman seeks sexual behaviour with her partner to enhance intimacy will often experience more satisfaction. Internal desires for closeness, connection and relatedness are the main drivers for sexual behaviour for people with intimacy motives (Cooper et al., 1998). Therefore, intimacy motives have a positive effect on daily psychological well-being and leads to greater relationship satisfaction.

Conclusion
The psychological theories of sexual motivation have little reference to the effect of hormones on sexual behaviour and motivation to engage. Regardless of this it is clear that hormones do play a role, and in humans in particular the behaviour is driven by more than just instinct.

It is often hard to show the correlation between endogenous hormone rhythms with sexual motivation. While most the disagreement stems from the fact that sexual motivations does not always require hormones to occur. Especially in women, we can engage in sexual activity regardless of hormonal state (Wallen, 2001).

Female hormones (progesterone, estrogen and oxyntic) are important for maintaining the female reproductive organs. If hormones were purely responsible for sexual motivation, we would not see advanced maternal age (AMA). Over the past three decades, there has been an increase of women who are choosing the delay pregnancy due to educational, social and economic reasons (Bayrampour, Heaman, Duncan & Tough, 2012). Women are most fertile and full of sex hormones in their late teens – early 20s, however, due to external reasons they are choosing to have children later. Even when women know the risks of an aging reproductive system there is a large group of women who are choosing to have children after 35 years or older (Bayrampour et al., 2012).

Central motive state does not activate sexual motivation by itself, an incentive stimulus is also required. (Agmo, 1999). This suggest that gonadal hormones and other physiological events are technically necessary for sexual motivation but aren’t the only contributing factors to sexual motivation. They facilitate the activation of the central motive state, but they aren’t the only thing to assist in activation (Agmo, 1999). Hormones also have an effect on the incentive stimuli. There is evidence showing that gonadal hormones alter the sensitivity of the sensory systems, enhancing the sexual incentive stimuli, therefore sexual motivation. Moreover, they may determine the impact of sensory stimulation has on the brain (Agmo, 1999).

Dopamine is one neurotransmitter system that may be upregulated by hormones that are associated with copulation. Dopamine agonists have been associated with increase sexual motivation and/or sexual potency of males (Hull, DU, Lorrain & Matuszewich, 1995). Futhermore, injections of dopamine agonist into the major regulatory site for male sexual behaviour, the MPOA, has produced effects that facilitated increased copulation. Previous reports suggest that dopamine is realized before and after copulation into the MPOA (Blackburn et al., 1992). Furthermore, a study focusing on the interaction affect between methamphetamine (METH) and dopamine, estradiol and progesterone. It was found that METH facilitated sexual motivation in female rats. It does this by increasing the extracellular concentration of all three hormones, in particular dopamine. The study also revealed that progesterone was necessary for METH facilitation of female sexual motivation and behaviour (Holder & Mong, 2010).

Futhermore, a study by Roney & Simmons (2013) investigated the hormonal signals that predict a variance in sexual motivation among naturally cycling women. They found a positive relationship between oestradiol and negative effects for progesterone on sexual motivation. They hypothesised that oestradiol concentrations from two days earlier will positively affect female sexual motivation on the current day, with testosterone and progesterone having an impact as well. As mentioned before, it was found that when oestradiol levels spiked, sexual motivation two days later was heightened. While as progesterone was found to be a consistent negative predictor across the two-day lag. Testosterone was found to have little to no effect on female sexual motivation in this study.

So what are the main points of this book chapter? To start off, everyone has different sexual motivations as for any behaviour we partake in.

However, hormones do play a role within sexual motivation. In males, increased levels of testosterone facilitate heightened sexual motivation and arousal. While in women, sex hormones, oestrogen, progesterone and oxytocin maintain the reproductive organs and increase sexual motivation around the time when they are most fertile.

Models of sexual motivation seek to explain the extrinsic and intrinsic motivations we have, the traditional sexual response cycle model developed by Masters and Johnson (1966) focuses heavily on physiological stimulation and achievement on orgasm as a motivator for sex. Although an applicable model for men, it lacked the emotional and intimacy motivators that women needed to reach the final phase or to even feel pleasure. The alternative model was a much more detailed cycle that included three stages of emotional value before arousal was obtained. These models were pivotal to begin the research the field of sexual motivation.

Further research, by Beach (1956), Hardy, (1964), Hill & Preston (1996) and other contributing psychologist found that there was much more to sexual motivation than stimulation, arousal and the other stages. They found that sex could be used and viewed as an incentive and that people in relationships used sex as a way in better their relationship or increase their self-esteem.

In conclusion, it is clear that there a more than one aspect which drives us to have sex. The combination of hormones and our search for arousal, pleasure, intimacy and satisfaction is in fact, what affects our sexual motivation.