Cross-modal recognition of human individuals in domestic horses (Equus caballus).

This research demonstrates that horses can recognize familiar humans using various senses either separately or in combination. The testing suggested that horses respond more intensively when the auditory, visual, or smell cues of a person they recognize are mismatched, indicating the integration of these cues in their brain for human recognition, even when some senses are unavailable.

Methodology

• The research used a cross-modal expectancy violation setup where the horses were exposed to both congruent (matching) and incongruent (mismatching) auditory and visual/olfactory cues from humans.
• The horses were presented with voices of both familiar and unfamiliar humans, sometimes without accompanying visual or olfactory cues. At other times, they were exposed to visual and smell cues of familiar and unfamiliar people without audio cues.

Findings

• Horses could discriminate between the voices of a familiar and an unfamiliar human even without seeing or smelling them. They were also able to tell the difference between the same persons using just visual and olfactory cues, without hearing their voices.
• Horses reacted more quickly, longer, and more frequently in trials where the auditory and visual/olfactory cues did not match. They exhibited a heightened interest in unmatched cues of identity, indicating recognition.

Implications

• The study suggests that a horse’s brain is able to integrate multiple sensory identity cues to form a representation of a familiar human. This means they can still recognize a familiar human even when one or two senses are unavailable.
• The finding of cross-modal recognition in horses asserts their cognitive complexity in terms of person recognition. It provides insights into their behavioral responses and could have important practical applications in horse-human interactions.