2.4 Explain, using examples, the function of two hormones on human behaviour

2.4 Explain, using examples, the function of two hormones on human behaviour

Cortisol and memory

Cortisol is a hormone produced by the adrenal cortex in response to stress and to restore homeostasis. Chronic stress may result in prolonged cortisol secretion and this can lead to physiological changes such as damaged immune system and impairment of learning and memory. This is because high amounts of cortisol results in atrophy of the hippocampus (Sapolsky, 1996).

Newcomer et al. (1999)

Aim: To investigate whether high levels of the stress hormone cortisol interfere with verbal declarative memory.

Method: It was a laboratory experiment. A self-selected sample (recruited through advertisement) of 51 normal and healthy people aged  18-30 was used. It was a randomized, controlled, double-blind experiment running for four days. All participants gave informed consent. Participants were split into three groups.

Group 1 (high dose cortisol) had tablets containing 160 mg of cortisol for four days.

Group 2 (low dose cortisol) had tablets with 40 mg of cortisol for four days.

Group 3 (control) had placebo tablets.

Participants listened to a prose paragraph and had to recall it as a test of verbal declarative memory.

Results: The results showed that group 1 performed the worst on the memory test compared to group 2 and group 3. The low-level groups showed no memory decrease.

Evaluation: The experiment shows that an increase in cortisol over a period has a negative effect on memory. This was a controlled, randomized experiment so it was possible to establish a cause-effect relationship between levels of cortisol and scores on a verbal declarative memory test. Ethical issues were observed with informed consent. The negative effect of taking high dosages of cortisol was reversible so no harm was done.

Oxytocin and trust

The hormone oxytocin is secreted by the hypothalamus and released into the bloodstream via the pituitary gland or into the brain and spinal cord where it binds to oxytocin receptors. Oxytocin acts primarily as a neurotransmitter in the brain. Oxytocin has been linked to trusting other people. Experimental manipulation of oxytocin levels has shown increase in trust. According to evolutionary psychologists, trust is an important social tool in the relationship between humans. Trust is an adaptive mechanism as it helps humans to form meaningful relationships at a personal and professional level. Betrayal disrupts bonds of trust and may result in avoidance of the person who has betrayed you. Oxytocin could play a role in reducing fear reactions via the amygdala that may arise as a consequence of betrayal.

Baumgartner et al. (2008)

Aim: To investigate the role of oxytocin after breaches of trust in a trust game.

Procedure: The participants played a trust game used by economists and neuroscientists to study social interaction. The ‘investor’ (player 1) receives a sum of money and must decide whether to keep it or share it with a ‘trustee’ (player 2). If the sum is shared, the sum is tripled. Then player 2 must decide if this sum should be shared (trust) or kept (violation of trust). fMRI scans were carried out on 49 participants. They received either oxytocin or placebo via a nasal spray. Participants played against different trustees in the trust game and against a computer in a risk game. In 50% of the games the trust was broken. They received feedback on this from the experimenters during the games.

Results: Participants in the placebo group were likely to show less trust after feedback on betrayal. They invested less. Participants in the oxytocin group continued to invest at similar rates after receiving feedback on a breach of trust. The fMRI scans showed decreases in responses in the amygdala and the caudate nucleus. The amygdala is involved in emotional processing and has many oxytocin receptors. The caudate nucleus is associated with learning and memory and plays a role in reward-related responses and learning to trust.

Evaluation: Oxytocin could explain why people are able to restore trust and forgive in long-term relationships. Scanner research is merely mapping brain activity but nothing definitive can be said about what it really means at this point in science. Giving oxytocin like this in an experiment may not reflect natural physiological processes. The function of oxytocin is very complex and it is too simplistic to say that it is ‘the trust hormone’.