IB Prosocial Behaviour - Marsh et al (2014)

Marsh et al. research method

Quasi-experiment

Marsh et al. aim

to examine potential biological origins of prosocial behaviour through examining possible differences in the brains of "extraordinary altruists" e.g. larger than average amygdala volume and faster responsiveness to fearful facial expressions.

Psychopath

a person who demonstrates a failure to empathise with others and thus show prosocial behaviour

Adrian Raine findings

reduced amygdala responsiveness to fearful facial expressions, reduced amygdala volume

Marsh et al. sample

19 altruistic kidney donors i.e. they had made a conscious decision to do something that significantly increases the risk to their own health for the sake of a stranger (12 men; 7 women)

How were Marsh's sample recruited?

national mail shot/electronic advertisements via local and national transplant organisations

Marsh control group

20 controls matched for IQ, income, education, psychological history, and medication use. The age range was from 23 to 56 years old.

Marsh procedure - stage 1

emotion recognition task in an fMRI; participants shown 120 images of faces showing one of six basic emotions

How did the images shown vary from each other (three IVs)

the emotion represented: anger, disgust, fear, happiness, sadness or surprise; the intensity of the emotion: high or moderate, the gender of the person: 5 male and 5 female for each emotion (6 expressions × 10 exemplars × 2 intensity levels).

Task when in the fmri scanner - dependent variables

Pps had to press a button to indicate which emotion was shown, time taken to decide was recorded

Marsh procedure stage 2

MRI scan to determine the structure of their brains

Marsh procedure stage 3

participants took tests to measure their level of psychopathy and empathy

Marsh results - amygdala size

extraordinary altruists had a greater average volume in the right amygdala than in the controls (right hemisphere associated with negative emotion, plays role in expression of fear ad processing fear-inducing stimuli )

Marsh results - amygdala responsiveness

faster response time in the right amygdala to fearful facial expression than in the control group. Opposite of what has been shown in research studying psychopaths.

Marsh conclusions

There may be a biological basis for altruistic behaviour