No abstract

Sixty-six mice of 11 genetic stocks (the Bailey recombinant inbred strains CXBD, CXBE, CXBG, CXBH, CXBI, CXBJ, CXBK; their progenitor strains, BALB/cBy and C57BL/6By: and the reciprocal hybrids, B6CF and CB6F) were tested in a two-compartment apparatus and in a shuttlebox, with five measures taken relating to activity and to approaches to novel and complex stimuli. A factor analysis of these measures revealed two factors, the first involving behavior relating to novel stimuli and the second relating to locomotor activity. In a second experiment, 132 mice of the same strains were tested on four of the measures used previously. On the two measures which had high loadings on the first factor and very low loadings on the second, it was possible to determine a strain distribution pattern (SDP), with the same SDP being found for both measures. When confirmed by testing mice from two congenic histocompatibility strains H(w54) and H(w80), we were able to determine that avoidance of novel/complex stimuli (neophobia) is controlled by a gene or genes at chromosomal segments H-24c and H-1b. It was also found that a polygenic model is consistent with behavior measured by the second (activity) factor.

Age and sex effects on stimulus exploration and locomotor activity were investigated in three genetic stocks of mice. Three measures of exploratory behavior and one measure of locomotor activity were recorded in an arena testing situation. The results showed that measures requiring locomotor activity are more affected by differences in age and sex than measures of stimulus exploration. The results are discussed in terms of the previously established genetic models of stimulus exploration and activity.

No abstract

Various studies have shown that fear, once acquired, can elicit avoidance behavior over relatively long periods of time, and that both these fears and the avoidance behaviors are unaffected by usual laboratory extinction procedures (Moyer, 1958; Solomon, Kamin, & Wynne, 1952).Mowrer (1951) has suggested that there are two distinct learning processes-the classical conditioning of fear and the instrumental conditioning of the avoidance response-occurring in the acquisition of an avoidance habit. Solomon & Wynne (1954), following Mowrer's paradigm, proposed the anxiety conservation hypothesis to explain the relatively greater perSistence of habits acquired under aversive stimulation. The present study was based upon two predictions derived from these theories: (1) If there are two distinctlearningprocesses in avoidance learning, then one should be able to extinguish one process (fear) separately, and by doing so facilitate extinction of the other (hurdle-jumping); (2) If the anxiety conservation hypothesiS is correct, then blocking the animal in the presence of fear-provoking situations should allow for the full fear reaction to occur and consequently result in its extinction. Further, the extinction of fear should facilitate extinction of the instrumental avoidance response. MethodThe experiment was divided into three phases: (1) A training phase, in which rats were conditioned to avoid a light; (2) a treatment phase, consisting of blocking animals in the presence of light; and (3) a normal extinction procedure. There were two replications of the study with 16 Sa serving in each. During the training phase, all Sa received 50 training trials in a shuttlebox, divided at the center by a 5 in.hurdle. A light preceded shock by 3 sec and both light and shock terminated when the animal crossed the hurdle. Following training, for the treatment phase, Sa were divided into four groups of four rats in each group. Groups were matched on sex and the number of avoidance responses given on