Hormones and Behaviour

Physiology

Testosterone

HPG axis: hypothalamus → pituitary → gonads (where testosterone is produced)

Theories abt testosterone

  • Challenge hypothesis: based on behaviour of birds that mate for life. Testosterone levels fluctuate based on competition levels between other male birds. Test levels decrease when the male bird finds a mate and starts to raise offspring. This is needed for the male to engage in parental care

Testosterone rises when competition is entered and won

Cortisol

HPA axis: hypothalamus → pituitary → adrenal glands

Produced as an EFFECT of stress, does not cause stress

  • Adrenaline response is initiated first after a stressful event

  • Cortisol needs 15 minutes to be produced and be able to affect behaviour

  • Homeostatic function: restores resting state to the brain (allostatic function)

Cortisol can build up if one is in a stressful environment or in people with anxiety disorders

Cortisol and testosterone are mutually inhibitory

C inhibits T production at each stage of the HPG axis, and vice versa

  • However this is not perfect, both can be simultaneously high and low. But a rise in one often causes a decrease in the other

T/C ratio predicts hierarchy

  • Gorillas with high T and low C are higher in the social hierarchy → winning competitions

    • In hierarchies are intimidation based the alpha male has low cortisol

  • Gorillas with high C and low T → losing competitions and experiencing stress

  • Baboons: the alpha male has high cortisol and high testosterone

    • When the hierarchy is established through physical fighting, the highest ranking individual will experience high stress as he has to often fight to keep his position

Human hierarchy: the T/C ratio is hard to use to determine this as our lives have various different hierarchies

Social Hierarchy

Hierarchies evolved as a means to allow individuals who climbed it to gain better access to power, resources, and mates

  • they are also important for the group, as a constant fight for status makes the group stronger

Dynamics

  • Social aggression → intimidation, symbolic ways of fighting

  • Physical violence is risky and thus not used by many species

  • Displays of dominance → physical and cultural, signalling (eg staring contest)

    • Gaze aversion is an example of a subordinate gesture

Adapted stroop tasks

  • Emotional: saying the colours of certain words which carry an emotional weight (eg people with arachnophobia take longer to read the colour of spider-related words)

Pictorial emotional stroop task: colour naming of facial expressions (subliminal or supraliminal)

  • Measuring the interference of expression on RT - does it make a difference if the face is happy, neutral, or angry? Males vs females, measuring testosterone and cortisol

  • The higher the testosterone level in the individual, the more interference was caused by the angry face (RT was slower)

  • Higher cortisol individuals showed anger facilitation → people were faster at naming the colour when the face was angry rather than happy or neutral

  • Theory: high cortisol made people avoid eye contact with an angry face as a signal of submission

  • Social anxiety: people were faster at naming the colour when they were unconciously primed with an angry face

    • T/C ratio: testosterone levels are lower, cortisol levels higher

  • Eye tracking study

    • People with high dominance motivation were slower to avert their gaze from angry faces

    • Testosterone administration vs placebo: people were slower to avert eye contact when given testosterone

    • Social anxiety: faster gaze aversion from angry faces → showing submissive behaviour

    • SA x testosterone: when given testosterone they maintained eye contact longer with angry faces, increased dominance

Neural Circuitry of T/C Aggression

Testosterone

  • Decouples OFC from amygdala → decreases regulation of the reactive threat system, increases reactively dominant/reactive aggression

  • Reactive threat system consists of the brainstem, hypothalamus and central/medial parts of the amygdala, regulated by OFC and amygdala

  • In animals: testosterone biases the threat system to fight over flight by upregulates vasopressin gene expression

Testosterone without social threat

  • OFC decoupling decreases emotional input to the cortex → might make one more rational or strategic

    • Even increases some prosocial behaviours such as cooperation, more fail decisions, more generosity, less lying

    • These decisions might help one to climb the hierarchy and maintain a high position there