VARIATION IN ACTIVITY SCORES AND SEQUENCES IN 2 INBRED MOUSE STRAINS, THEIR HYBRIDS, AND BACKCROSSES

Nine hundred and twenty-two mice, consisting of DBA-1J, C57BL/6J, their F1, F2, and back-cross generations were tested in a barrier activity cage. The exact sequence of acts of each animal in the cage was recorded during a 5-min test period. Observed were two aspects of grooming behaviour, jumping and peeking over the barrier, and a defecation score. The mean number of motor acts per animal was highest in C57BL, lowest in DBA, intermediate in hybrids. Grooming scores gave some evidence of heterosis. Estimates of degrees of genetic determination varied from zero for peeking to 46 per cent for jumping. Typologies of the trajectory of the animal in time have been worked out by means of a nonmetric computer technique, Multidimensional Scalogram Analysis. Examples are presented of three subsamples of profiles, 150 each, showing well-defined DBA and C57BL regions in a two-dimensional space. The behavioural features distinguishing these regions are evaluated by analyses of certain stages in the behaviour sequences as printed by the computer. There is evidence for considerable dominance of the DBA behaviour pattern, with distribution of F2 profiles indicating genetic segregation. Two specific acts in the sequence, the 7th and 23rd, were found to provide optimal discrimination between the DBA and C57BL animals. © 1969.