Lateralization of rotational behavior in developing and adult hamsters

Rotational asymmetries were studied in developing and adult hamsters, and compared to verify if early lateralization is a predictor of the animals' later performance. Animals were divided into two groups: group I (GI) was tested from P46 (P1 = day of birth) to P62, and group II (GII) was tested daily from P2 to P60. They were placed in a cylindric arena for 5 min under video recording, and their 90 degree right and left displacements were counted and normalized. Since adult animals of both groups did not differ significantly in the distribution of asymmetries, the data were pooled together: 38.8% were non-lateralized (NL), 39.4% were right-rotators (RR), and 21.8% were left-rotators (LR). No significant difference was discerned between males and females. Distribution of asymmetries in GII animals between P2 and P10 showed a predominance of lateralized (64.7% RR and 21.5% LR) over NL animals (13.8%). The proportion of pups that maintained their classification into adulthood was only 46%, and the kappa coherence coefficient for these data was only 0.09. We conclude that: (1) most adults are lateralized, RR being more frequent; (2) the proportion of lateralized adults is not significantly altered by early testing; (3) there is no significant difference between males and females; (4) most developing hamsters are lateralized, right-rotators being more frequent; and (5) the animals' early classification is not a good predictor of their preference as adults.