Human facial recognition in fish

C Newport1, G M Wallis2, U E Siebeck1

1School of Biomedical Sciences, The University of Queensland, Australia
2School of Human Movement Studies, The University of Queensland, Australia


There are currently two conflicting theories of how humans recognise faces: (i) recognition processes are innate, relying on specialised cortical circuitry, and (ii) recognition uses the same neural circuitry as other object classes and is simply a learned expertise. One method to determine the underlying mechanisms is to ask whether animals without specialised neural circuitry, or indeed a cortex, can complete this task. We tested fish to determine whether they could learn to discriminate human faces. Using a two-alternative forced-choice test, four archerfish (Toxotes chatareus) were trained to select a rewarded face image. All fish could select the correct face from 45 distractors with an accuracy of over 75% (p<0.05). Humans tested using the same stimuli reached a higher level of performance. However, archerfish performing a much simpler task involving shapes (e.g. cross and square) revealed similar levels of performance, suggesting that fish find human faces just as easy to discriminate as shapes. This study provides the first behavioural evidence that an animal lacking a cortex, and relatively little exposure to human faces, can nonetheless discriminate them to a high degree of accuracy. Our results suggest that a substantial part of the face discrimination task can be learnt.

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