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Adult but not juvenile Barbary macaques spontaneously recognize group members from pictures.

Schell A, Rieck K, Schell K, Hammerschmidt K, Fischer J - Anim Cogn (2011)

Bottom Line: This ability appears to develop with age, as juveniles did not discriminate between members of their own group and another group, although they showed generally more interest in the pictures than did adults.Whether the difference in behaviour is based on individual recognition of one's own group members or simply the discrimination based on familiarity remains unresolved.However, both mechanisms would be sufficient for group membership identification.

View Article: PubMed Central - PubMed

Affiliation: Cognitive Ethology Lab, German Primate Center, Göttingen, Germany.

ABSTRACT
For group-living animals, it is crucial to distinguish one's own group members from those of other groups. Studies applying operant conditioning revealed that monkeys living in relatively small groups are able to recognize their own group members when tested with photographs of group members and other conspecifics. Employing a simple looking time paradigm, we here show that Barbary macaques living in two social groups comprising 46 and 57 individuals, respectively, at the enclosure 'La Forêt des Singes' at Rocamadour are able to spontaneously distinguish photographs of members of their own group from those depicting animals that belong to another group. This ability appears to develop with age, as juveniles did not discriminate between members of their own group and another group, although they showed generally more interest in the pictures than did adults. Juveniles frequently displayed picture directed behaviours such as lip-smacking, touching and sniffing in both conditions, indicating that the stimuli were highly salient to them. In conclusion, it appears that at least adult monkeys are able to memorize the faces of a large number of individuals. Whether the difference in behaviour is based on individual recognition of one's own group members or simply the discrimination based on familiarity remains unresolved. However, both mechanisms would be sufficient for group membership identification.

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Example of portrait photographs of the two tested groups used as stimuli (GB Grand Bassin, PB Petit Bassin)
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Fig1: Example of portrait photographs of the two tested groups used as stimuli (GB Grand Bassin, PB Petit Bassin)

Mentions: We took portrait photos for stimuli using a Nikon D90 digital reflex camera (Nikon Corporation, Tokyo, Japan) equipped with a telephoto lens with a focal length of f = 18–200 mm. Two groups (“Grand Bassin”: 46 individuals; “Petit Bassin”: 57 individuals) out of the three served as test groups. Eight portraits of adult animals (i.e. females from the age of five and males from the age of seven) with a neutral facial expression (see Teufel et al. 2010) were chosen from each group, with the same number of males and females (Fig. 1). All faces were cropped using Adobe Photoshop CS3 (Adobe Systems, Incorporation, San Jose, California, USA), so that the facial features were fitted into a circle of a diameter of 17 cm. The luminance did not differ significantly between groups (Mann–Whitney U = 24.5, N1 = N2 = 8, P = 0.43). Photographs were printed on matte photo paper to avoid any reflection during the testing session. This resulted in a set of 16 stimuli that served both as ‘own group’ or ‘other group’ stimuli, depending on the group in which the experiments were conducted. To control for possible effects of the experimental setting, we introduced an additional condition in which a white sheet of paper was shown.Fig. 1


Adult but not juvenile Barbary macaques spontaneously recognize group members from pictures.

Schell A, Rieck K, Schell K, Hammerschmidt K, Fischer J - Anim Cogn (2011)

Example of portrait photographs of the two tested groups used as stimuli (GB Grand Bassin, PB Petit Bassin)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3117280&req=5

Fig1: Example of portrait photographs of the two tested groups used as stimuli (GB Grand Bassin, PB Petit Bassin)
Mentions: We took portrait photos for stimuli using a Nikon D90 digital reflex camera (Nikon Corporation, Tokyo, Japan) equipped with a telephoto lens with a focal length of f = 18–200 mm. Two groups (“Grand Bassin”: 46 individuals; “Petit Bassin”: 57 individuals) out of the three served as test groups. Eight portraits of adult animals (i.e. females from the age of five and males from the age of seven) with a neutral facial expression (see Teufel et al. 2010) were chosen from each group, with the same number of males and females (Fig. 1). All faces were cropped using Adobe Photoshop CS3 (Adobe Systems, Incorporation, San Jose, California, USA), so that the facial features were fitted into a circle of a diameter of 17 cm. The luminance did not differ significantly between groups (Mann–Whitney U = 24.5, N1 = N2 = 8, P = 0.43). Photographs were printed on matte photo paper to avoid any reflection during the testing session. This resulted in a set of 16 stimuli that served both as ‘own group’ or ‘other group’ stimuli, depending on the group in which the experiments were conducted. To control for possible effects of the experimental setting, we introduced an additional condition in which a white sheet of paper was shown.Fig. 1

Bottom Line: This ability appears to develop with age, as juveniles did not discriminate between members of their own group and another group, although they showed generally more interest in the pictures than did adults.Whether the difference in behaviour is based on individual recognition of one's own group members or simply the discrimination based on familiarity remains unresolved.However, both mechanisms would be sufficient for group membership identification.

View Article: PubMed Central - PubMed

Affiliation: Cognitive Ethology Lab, German Primate Center, Göttingen, Germany.

ABSTRACT
For group-living animals, it is crucial to distinguish one's own group members from those of other groups. Studies applying operant conditioning revealed that monkeys living in relatively small groups are able to recognize their own group members when tested with photographs of group members and other conspecifics. Employing a simple looking time paradigm, we here show that Barbary macaques living in two social groups comprising 46 and 57 individuals, respectively, at the enclosure 'La Forêt des Singes' at Rocamadour are able to spontaneously distinguish photographs of members of their own group from those depicting animals that belong to another group. This ability appears to develop with age, as juveniles did not discriminate between members of their own group and another group, although they showed generally more interest in the pictures than did adults. Juveniles frequently displayed picture directed behaviours such as lip-smacking, touching and sniffing in both conditions, indicating that the stimuli were highly salient to them. In conclusion, it appears that at least adult monkeys are able to memorize the faces of a large number of individuals. Whether the difference in behaviour is based on individual recognition of one's own group members or simply the discrimination based on familiarity remains unresolved. However, both mechanisms would be sufficient for group membership identification.

Show MeSH