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Abstract

Herrnstein and Loveland (1964) showed that pigeons are capable of people-present/people-absent concept
discrimination. Yamazaki et al. (2007) suggested that the use of concept-based strategy is lateralized in
birds. In their study birds showed categorization superiority with the right eye (left hemisphere). To further
our understanding of the role of each hemisphere in categorization behaviour, we examined concept
discrimination in birds while one hemisphere or the other was deactivated. Pigeons were trained in a go/no-
go procedure to discriminate pictures of humans and to transfer to novel exemplars. To examine which
hemisphere was involved in categorization, an additional transfer test was conducted
while the left or the
right entopallium was blocked with Tetrodotoxin. On the transfer test, the birds were tested with both
previously learned as well as novel people-present/people- absent instances. Discrimination of learned
stimuli was not impaired when either the left or the right hemisphere was blocked. However, concept
discrimination of the novel instances was impaired when the left hemisphere was blocked, although they
still performed the discrimination above chance. This suggests that the left hemisphere was superior in
category-specific processing, whereas the right hemisphere is just capable of discriminating between the
known stimuli, thus relaying on a memorization strategy. Our findings of an asymmetrical cognitive
architecture in birds are largely shared with humans and might have a long phylogenetic history.