The stability and interest consonance of lateral postural--motor biases in rats: results and implications.

Each of six different tests of lateral postural-motor asymmetries was repeatedly administered to 126 rats. Directional reliability was found for rotatory swimming, open-field exploration, and stepping down from a beam. Neonatal posture, turn in an unbaited T maze, and orientation to tail pinch proved not to be reliable across days. The behavioral asymmetries in the open-field and step-down tests were directionally consonant with each other, but neither was related to the asymmetry exhibited in rotatory swimming, implying the existence of at least two independent asymmetrical neural substrates underlying the behaviors. Neither sample-wide directional biases nor major sex differences in bias were found. The sexes were, however, differentially influenced in direction on some tests by the number of males in their natal litters, implying a role for intrauterine exposure to androgens in predisposing rats toward some left- or right-biased behaviors.