Are faces special for sheep? Evidence from facial and object discrimination learning tests showing effects of inversion and social familiarity

Configurational coding, familiarity and the right hemisphere advantage for face recognition in sheep

“…The ®nd-ings may explain Kendrick et al's [18] ®nding that the inversion e ect of sheep face recognition is greater with familiar faces. It also supports the suggestion of others [31,32] that inversion e ects are the result of con®gurational or global coding methods used extensively in the recognition of faces.…”

“…Sheep have been shown to use visual cues to discriminate between the species or breed of faces presented in a Y-maze [4] as well as identifying faces of individual sheep [18]. In both studies signi®cant classic inversion e ects were found for the faces of a familiar breed, and especially for socially familiar individuals [18].…”

“…In both studies signi®cant classic inversion e ects were found for the faces of a familiar breed, and especially for socially familiar individuals [18]. In sheep, neither electrophysiological nor behavioural studies have previously attempted to identify any asymmetry, although recent data from in-situ hybridisation of c-fos has shown stronger right hemisphere activation during a face recognition task [19].…”

Behavioural and neurophysiological evidence for face identity and face emotion processing in animals

“…Sheep also show classical inversion effects with faces but not objects and can use configural cues from the internal features of faces in the same way as we do (Kendrick et al 1996;Peirce et al 2000). They learn to discriminate between the faces of socially familiar individuals to obtain a reward more quickly than with unfamiliar ones (Kendrick et al 1996) and can remember faces of conspecifics for a period of up to 2 years (Kendrick et al 2001c). They can also recognize different human faces and show inversion effects, although they take longer to learn to discriminate between them (Kendrick et al 1996).…”

“…They learn to discriminate between the faces of socially familiar individuals to obtain a reward more quickly than with unfamiliar ones (Kendrick et al 1996) and can remember faces of conspecifics for a period of up to 2 years (Kendrick et al 2001c). They can also recognize different human faces and show inversion effects, although they take longer to learn to discriminate between them (Kendrick et al 1996). Under freeviewing conditions, Peirce et al (2000) found evidence for a left visual-field bias (right-hemisphere advantage) for familiar, but not unfamiliar, sheep faces using a series of experiments using chimeric face composites, an effect also found in human face processing.…”