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

Area of Science:

• Animal cognition
• Neuroscience
• Behavioral science

Background:

• Sheep possess sophisticated visual recognition abilities.
• Understanding face recognition in non-primate species offers insights into visual processing.
• Lateralization of visual processing is well-documented in primates but less so in other mammals.

Purpose of the Study:

• To investigate visual face recognition in sheep, focusing on familiar vs. unfamiliar individuals.
• To determine the role of visual field lateralization in sheep face recognition.
• To examine the differential use of internal (configurational) and external facial features.

Main Methods:

• A Y-maze discrimination task was used to train sheep to identify target faces.
• Stimuli included 'hemifaces', 'mirrored hemifaces', and 'chimeric' faces to test visual hemifield use.
• Experiments assessed recognition using only external features and only internal features.

Main Results:

• A left visual hemifield (LVF) advantage was observed in identifying hemifaces, mirrored hemifaces, and chimeric faces, particularly for familiar faces.
• Both familiar and unfamiliar faces could be identified using external features alone.
• Only familiar faces were recognizable using internal features alone.

Conclusions:

• Sheep exhibit distinct visual recognition strategies for familiar and unfamiliar faces.
• Familiar face recognition in sheep is associated with internal, configurational cues and a left visual field bias.
• This study provides evidence for visual field bias in face recognition outside of the primate literature.