Detecting reliable nonverbal and paralinguistic signals of cooperativeness in strangers

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• William Brown (Brunel University, London)
• Wednesday 29 October 2008, 12:30-13:30
• Library, Sub-Department of Animal Behaviour.

If you have a question about this talk, please contact Diane Pearce.

Altruist detection is a critical component of adaptive cooperation: if genuinely altruistic individuals are detectable, then defectors can be avoided and cooperation can more easily evolve. This study investigated whether genuine altruistic dispositions are detectable solely from biological motion and vocal signals. Thirty males, who were pre-assessed using implicit and explicit measures of altruistic disposition, moved boxes in two conditions: for personal benefit (earning £1 per box moved), and for a stranger’s benefit (who received £1 per box moved). The payoff structure was designed to encourage selfish and unselfish behaviour in the respective conditions. In order to isolate biological motion signals from other signaller characteristics (e.g. attractiveness, identity etc.) motion-capture technology was utilised: seven motion capture cameras recorded three-dimensional movement of 40 reflective markers placed on the box mover’s head and body. Caloric expenditure during box lifting was measured using an energy expenditure monitor. Evaluators, blind to cooperative disposition of signaller, rated gait motions of more genuinely altruistic individuals as more “unselfish”. In a second study the voices of males and females pre-screened for level of altruism were recorded and band-pass filtered to test if altruist-detection from voice was possible. Evaluators were accurate at detecting altruism level from signallers’ vocalisations. More altruistic females had higher pitched voices than less altruistic females. The reverse was marginally the case for males. These results are the first unequivocal demonstration that genuine altruism is detectable solely from nonverbal and paralinguistic signals.

This talk is part of the Madingley Lunchtime Seminars series.

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• Library, Sub-Department of Animal Behaviour

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