Discrimination of familiar and unfamiliar human voices is independent of prolonged human-animal interaction in domestic chicks

Different animal species, both domestic and wild, can discriminate between various human cues, such as voices, and adjust their behavior based on whether they are familiar or unfamiliar with these cues. To investigate whether this ability extends to a domesticated species not specifically bred for human interaction and whether it can manifest at an early age, even under commercial-like conditions with limited human interaction, we conducted human vocal discrimination tests on domestic chicks at two ages (25 and 67 days old). Our findings showed that chicks could discriminate between familiar and unfamiliar voices at both ages, exhibiting increased vigilance when a known sentence was spoken by an unfamiliar voice compared to a familiar voice. We also found that chicks were more vigilant after a familiar voice delivered an unknown sentence, compared to an unfamiliar voice delivered a known sentence. This suggests a violation of expectation when animals are confronted with mixed familiar/unfamiliar heterospecific signals. Our findings support that neither specific selection for interaction with humans, nor an extended history of exposure to humans, is a prerequisite for animals to discriminate heterospecific cues, such as human voices.