What are hormones?
“Chemical messengers”
Chemicals released into the bloodstream which interact with cells to alter a biological process (or processes)
Released by endocrine glands
(Hence: study of hormones = endocrinology; study of hormone effects on behaviour = behavioural endocrinology).
- Similar to neurotransmitters? (esp. proteins, peptides)
- Communicate information from a cell which releases them to another cell with receptors for them.
What are the two types of hormones?
- Proteins, peptides, modified amino acids
Bind to cell-surface receptors to alter cell function via second messengers - Steroids
Pass across the cell membrane,
bind to structures within the cell
and then to DNA to alter gene
expression.
When do chemicals act as hormones?
– Released at a distance from its target cell
– Carried to the target cell in the blood
When do chemicals act as neurotransmitters?
– It is released by a neuron and acts on an adjacent cell.
– Its action has a clearly defined onset and end.
What is the difference between hormones and neurotransmitters?
Hormone takes longer to cause an effect than a neurotransmitter; its effects usually last longer; it works over a greater distance; and neurotransmitters target neurons.
What is the sex hormones secreted by?
*Secreted by the gonads (ovaries or testes) and by the adrenal glands
*Androgens - have masculinizing effects,
– testosterone
*Estrogens - have feminizing effects
–estradiol
*All types present in each sex
*Drive the development of the fetus
What are organisational effects?
- Hormones act during development to influence physical maturation
- Influence brain and sex organ development
- May occur during critical periods in development when certain hormones are released.
- Effects tend to be enduring, may be permanent.
What are activational effects?
- Occur after the development of sex hormones
- Later in life
- Tend to be temporary
Effects related to changes in levels of hormones at any given time (Effects less likely to be enduring or permanent). - E.g. changing cortisol levels in response to a stressor;
- E.g. seasonal variations in sexual behaviour in many animal species related to seasonal patterns
of hormone release.
BUT (recurring theme): complex interactions between behaviour and hormonal release and influence.
Explain the sexual development in males and females.
- Female XX
- Male XY
- 6 weeks after conception the testes or ovaries develop.
- Later, the internal sex organs develop driven by hormones released from the testes.
What are the different hormones?
Cortisol
Testosterone
What does the cortisol do?
- Facilitates glucose use (energy)
- Facilitates breakdown of fats for energy use
- Stimulates arousal
- May facilitate cognitive functions?
Generally: sensitizes behaviours appropriate to dealing with an acute stressor.
What is testosterone?
Is a hormone belonging to the class of androgens
Present in females as well as males (primarily via adrenal gland)
Effects on development of sexual characteristics
Explain the indirect evidence that androgen plays a role in aggression.
*Levels of aggression typically higher in male animals than females
* Aggression often associated with reproductive activities;
* Aggression elevated from around time of puberty (humans and other animals);
* Seasonal changes in androgen levels correlates with seasonal changes in aggression for some species.
What are the organisational effects of testosterone?
Refer to the long-lasting structural and functional changes in the brain and body that occur during critical periods of development, particularly during prenatal and early postnatal stages.
What are the prenatal testosterone’s organizational effects?
Refer to the influence of testosterone exposure during fetal development on the organisation of brain structure, function, and behavior later in life.
- Leads to male behaviours in later life
e.g. Women with CAH (exposed to excess androgen prenatally) show increased male-typical toy, playmate, and activity preferences (Hines, 2011).
- Affects male-female interactions (Moskowitz et al., 2015)
- Men who experienced higher levels of testosterone exposure before birth tend to favour women in their adult
social interactions.
What are the effects of removing testosterone?
Removing testosterone: castration
- Castration in many animal species can reduce aggression; this can be reinstated by injections of testosterone
- But evidence in humans is not very useful they are either old studies poorly conducted and newer studies of “chemical castration” are inconsistent (perhaps reduces sexual assaults?)
Consequences of adding testosterone: injecting testosterone
* Injections of testosterone increase subjective reports of feeling “hostile” (Dabbs et al., 2002).
Testosterone injections also affect cognitive processing of aggression-related stimuli:
Van Honk et al. (1999)
Testosterone + happy (or neutral) face = no change in heart rate
Testosterone + angry face = increase in heart rate.
Illustrates the sensitizing effect of testosterone.
Explain correlational studies of testosterone’s relationship to aggression.
- Correlate levels of testosterone with levels of aggressive behaviour
- Animals: extensive evidence (e.g. seasonal covariation)
Activational effects of testosterone
Humans: - Significant correlation between testosterone levels and anti-social behaviour …
- … But only for men of low socioeconomic status (Bernhardt, 1997; Dabbs & Morris, 1990)
- Engaging in aggressive behaviours can increase testosterone levels. (Klinesmith, et al., (2006).
Dabbs et al. (1987): Male prisoners - levels of testosterone correlated with rule transgressions, external ratings of toughness, violence of criminal act.
- But looking across studies of prisoners, correlations tend to be rather weak (Archer, 1994).
Give examples of female aggression.
- Territorial defence (less common than males);
- Maternal defence; Status hierarchies.
Explain research on female aggression and correlation with testosterone.
Dabbs et al. (1988):
* Compared female prisoners
categorised by type of crime -
* (a) unprovoked violent (b) defensive violent; testosterone levels higher in (a) or women in (b)?
Dabbs and Hargrove (1997) testosterone related to behaviour in prison (a) aggressive, (b) passive or (c) neutral
* However, testosterone was not related to criminal violence. While aggressive dominance and violent crime did not correlate.
Explain testosterone’s role in competitive behavior
- Levels increase in response to success in competitions compared to losers in males and females (Geniole, et al, 2017)
- Levels can decline after loss of aggressive encounter (Bernstein
et al, 1974) - In a wide variety of sports, winning an athletic competition is associated with an increase in T for both men and women.
- Female football players showed changes in testosterone (Oliveira et al, 2009) similar to males.
- Athletic competition in women is associated with an increase in T and C regardless of whether the contest is won or lost (e.g. Edwards and Kurlander, 2010; Casto et al., 2014;
Casto and Edwards, 2016).
Explain testosterone’s role in dominance.
- Mazur (1985) distinguished dominance and aggression.
- Archer (2006) concluded that the literature indicates an association between testosterone, aggression, dominance and status striving.
- Testosterone effect on dominance dependent on cortisol (Meta & Josephs, 2010).
