Picture recognition in animals and humans

D. Bo6et, J. Vauclair/Beha6ioural Brain Research 109 (2000) 143-165

Table 1 (Continued)

recognition in animals. Thus, a study by Vandenheede
and Bouissou [101] indicates that sheep recognised a 2-D
stimulus at its first presentation. In this study, the fear
reactions of ewes were tested when the subjects were
separately presented with a full-size slide of a human, a
sheep, or a control stimulus (a traffic cone); the ewes
showed reduced fear reactions in the presence ofa sheep’s
photograph, as with real conspecifics and, moreover,
sniffing was primarily directed towards the anogenital
region and the head, which corresponds to behaviours
directed towards real conspecifics. However, the human
slide failed to induce fear reactions, as they occurred with
a real human or even a human-like model [101], thus
suggesting the possibility that recognition of 2-D stimuli
could be easier when stimuli are conspecifics. A subse-
quent experiment [4] showed that, in ewes, a slide of an
unknown individual of its own breed significantly re-
duced fear reactions compared to a slide of an unknown
individual of a different breed, this latter result suggest-
ing that the ewes can recognise the characteristics of their
breed on the slide.

Finally, Clun Forest and Dalesbred sheep showed an
ability to discriminate black-and-white photographs de-
picting faces of sheep versus human faces when they were
tested with a procedure of spontaneous choice in a
Y-maze [54]. In addition, the same study demonstrated
that Clun ewes could also distinguish between the faces
of male and female breed members and between a trough
with and without food. Moreover, some subjects were
observed displaying overt social reactions toward stimuli,
such as licking the pictures (C. Fabre-Nys, pers. com-
mun., May 1998).

3.1.2. Reactions to motion pictures

Plimpton et al. [77] showed social stimuli (for example
a threatening male stimulus) to juvenile bonnet macaques
via colour videotape recordings and observed these
subjects in the presence of their mother; they exhibited
appropriate responses depending on the nature of the
social display, that is, they behaved submissively toward
the threatening male and searched for contact with their
mother while they approached a passive female. Herzog
and Hopf [42] showed different colour films to wild-born
and laboratory-born squirrel monkeys. While the presen-
tation of predators (cats, snakes or avian predators)
caused specific alarm and flight reactions, the subjects did
not emit any alarm response when nonpredator mam-
mals were shown. Further, they reacted in the same way
as they did in real situations upon seeing preparation of
food or insects walking and also reacted to films of
human beings as to real people. These subjects demon-
strated face recognition; upon seeing in the film a
caretaker who had recently removed a dead neonate, the
squirrel monkeys behaved as if they were facing a real
terrestrial predator. No difference was shown between
wild and laboratory born-subjects.

In studies with birds, the use of predators’ pictures
also yielded positive indications of picture recognition.
For example, in a study by Evans and Marler [34]
which used video images as stimuli, domestic cockerels
were shown to respond with similar alarm calls in
response to an aerial predator model when either videos
of hens or real caged hens were present. The use of
social stimuli, notably in tasks requiring the recognition
of conspecifics, can provide important insight on the
ability of birds to match objects with their pictures.
Shimizu [90] observed that when video images of fe-
males were presented to male pigeons, the duration of
the males’ social display was not significantly different
from that which they performed in front of the live
bird. When video images of another bird (a cockatoo)

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