Complex Visual Concept in the Pigeon

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Science  23 Oct 1964:
Vol. 146, Issue 3643, pp. 549-551
DOI: 10.1126/science.146.3643.549


Pigeons were trained to respond to the presence or absence of human beings in photographs. The precision of their performances and the ease with which the training was accomplished suggest greater powers of conceptualization than are ordinarily attributed to animals.