ABSTRACT
Photo-, computo-, and videographic pictures have been popular stimuli in experimental studies on the cognitive capacities of pigeons. Most authors have simply considered them as complex stimuli but some authors have talked about them as being natural stimuli. More popular accounts of these studies have mostly assumed that the pigeons were recognising the equivalencies between the pictures presented and the objects or scenes that were represented on them. We argue that this assumption may often not be warranted because picture technology is adjusted to fool human vision but not pigeon vision. Mammalian and avian visual systems have a long divergent evolutionary history. Anatomical, physiological, and behavioural investigations indicate that colour, depth, flicker, movement and other aspects of vision are probably sufficiently different from humans in pigeons and other birds, enough for pictures to appear to them quite different from reality. We review a number of studies in pigeons and chickens that were concerned with the cross-recognition of real objects or scenes and pictures thereof. The conclusion is that these animals are capable of some gross transfer of recognition between pictures and reality and vice-versa but that when the behavioural tasks require more complex or refined discriminations this transfer generally brakes down.
