Individual variation in play in young chickens - assessment and connection to affective state and personality.

The extent of individual variation in play frequency, and its association with affective state and personality is unexplored. We evaluated two different methods to study individual variation: video stimulation and individual consistency across different group constellations. In both cases, the birds were moved from the home pen to identical play arenas, and the play sessions were video recorded. Furthermore, a cognitive judgement bias test was performed, and in one group, personality tests were also performed. Large variation in individual play frequency was observed with both methods. Video stimulation did elicit some play behaviour, but the play frequency was lower than expected, and no social play was observed. Individual play frequency was relatively consistent across test days when chicks were allowed to play in different groups, suggesting a possible genetic influence on play motivation. No connection between individual play frequency and affective state was found, suggesting that play is weakly associated with fundamental state of affect in chicks. Furthermore, the results revealed a negative correlation between food exploration and total play in females, and between food exploration and affective state in males. This suggests that food motivation was greater in females who played less and in males exhibiting greater optimism.