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to a picture as they would react, spontaneously or after
some training, to the real object. Of course, such reac-
tions may vary according to the type of presented
pictures: social behaviour with pictures of conspecifics,
fear with threatening stimuli, predator behaviours with
pictures of prey, etc.; spontaneous responses and trans-
fer of various acquired responses (naming, categorisa-
tion, discrimination, cross-modal matching, etc.) in
other cases. The second category encompasses the ex-
periments which could indicate the existence of picture
recognition but are not really demonstrations because
the experimental design is questionable (for example
when only one subject is involved) or the results (sub-
jects’ preferences or time viewing, discrimination of
individuals or species, or various spontaneous be-
haviours) are not necessarily specifically elicited by the
presented stimuli. The third category includes those
experiments which show that animals may have
difficulties with picture recognition.
In addition, two subclasses may be distinguished
among the studies that have used pictures of living or
inanimate objects with animal subjects; the first class
referring to the studies examining learned reactions to
stimuli (as it is often the case when the subjects are
primates or birds), while the second class of studies
measures spontaneous or natural reactions to the stim-
uli (this type of study is frequently seen in experiments
involving lower vertebrates or invertebrates). In this
latter case, a very salient feature of the releasing stimu-
lus can suffice to induce the reaction. For example, a
male redbreast reacts to a lure (e.g. a red tuft of red
feathers) as if it were a real conspecific, even if the lure
does not look like a bird [61]; a colour photograph of a
male conspecific may induce a similar reaction but it is
not certain whether, in such cases, the whole stimulus
has to be processed and recognised. However, when a
subject is trained to respond to real stimuli and then
transfers its response to pictures of those stimuli, or is
able to use video images to acquire some information
about the nature of a real object, this suggests that the
most significant features of the pictured stimuli are
considered and recognised. Therefore, as picture pro-
cessing can differ as a function of the kind of response
(spontaneous or learned), these two classes will be
considered separately.
A third classificatory key concerns the issue of the
stimuli presented, that is, whether the image is static
(photography, slide, digitised picture) or a motion pic-
ture, which of course implies some movement and often
sound and may thus greatly facilitate the subjects’
reaction to the stimuli. For example, movement is well
known as releasing predatory behaviour [11], or may
play an important role in the courtship of many species
(see for example Refs. [35,94]).
2. Studies with humans: cross-cultural and
developmental studies
Even in humans, recognition of photographs or pic-
tures is not as straightforward as it may first appear.
Thus, Miller [70] showed that there are intercultural
differences in picture perception, with humans who
have never seen pictures having difficulty recognising
what is represented in black-and-white photographs;
this author gives an example originally reported by
Herskovits ([41], cited in Miller [70]) who imparts that
a Bush Negro woman was initially unable to recognise
a photograph of her son until details were pointed out
to her. Similarly, Miller cites Kidd [56] who reported
that Bantus expressed difficulties in recognising objects
in photographs until the details of those objects were
highlighted to them and they then perceived them al-
most instantly. Deregowski et al. [29] encountered the
same difficulties with a remote Ethiopian population,
but these authors emphasised that members of this
population were able to gradually recognise drawings
but with considerable effort and seemingly finding the
task stressful.
Kennedy [55] has suggested that the subjects studied
by Deregowski and his colleagues could have initially
recognised details and then progressively built up a
composite structure of the picture. Miller [70] has also
shown that even when people recognise objects as rep-
resented in pictures, they may experience problems
perceiving the third dimension; thus, depth is often not
seen. For example, objects which were represented in
the background appeared to some subjects as being
placed upon objects represented at the forefront of the
picture. Miller concluded that the ‘‘insight that pro-
duces an overcoming of flatness cues may require very
little experience with pictures, but experience in perceiv-
ing objects in the three-dimensional world is not suffi-
cient to perceive those objects in pictorial
representations and that direct experience with pictures
might also be necessary for the perception of depth cues
in pictorial materials’’ ([70], p. 148). Deregowski [28]
also relied on cross-cultural studies to understand the
mechanisms of the perception and representation of
space; coming to the conclusion that even if people
unfamiliar with 2-D representations had more
difficulties with picture recognition, the same kind of
difficulties could occur in pictorial and nonpictorial
cultures.
An interesting experiment has presented results that
contradict the preceding conclusions. Hochberg and
Brooks [44] studied the behaviour of a child brought up
until the age of 19 months without being exposed to
pictures; when tested at the end of this period, this child
was able to recognise and to name various objects from
his familiar environment represented in photographs
and line drawings. However, this child’s environment