Arousal and T-maze choice behavior in mice: A convergent paradigm for neophobia constructs and optimal arousal theory

Three experiments investigating the effects of arousal on the T-maze choice behavior of inbred mouse strains are reported. In Experiment 1, CBA and NZB mice were administered unrewarded free choice alternation tests on 10 consecutive days under either No Shock, Shock Start (shocked in the start box), or Shock Choice (shocked at the choice point) treatment conditions. Both strain and treatment effects were observed: In the No-Shock condition, the nonreactive CBA strain alternated, but the reactive NZB strain did not. In the Shock Start condition the CBA strain showed only a suppressed alternation, while the NZB strain administered the same treatment perseverated. Both strains perseverated in the Shock Choice condition. In Experiment 2, NZB mice administered identical shocks in the start box and goal arms on both trials of five consecutive tests conducted once a day perseverated to the same goal arm in which they had been shocked on the first trial. In Experiment 3, NZB mice punished for perseverating (with shock continuation) and simultaneously reinforced for alternating (with shock termination) showed a “punishment paradox”; they perseverated despite the reinforcement contingencies. These results, which are congruent with the optimal arousal theory and several characteristics the theory shares with the emergent neophobia construct, support the contention that arousal mediates a symmetrical relationship between approach and avoidance along a novelty-familiarity continuum.     

Time reallocation in a multiresponse environment: Effects of restricting response classes

Four adult male rats were each placed for three hours daily into an apparatus that provided individual compartments for six separate location-defined responses. The available responses consisted of: (1) the opportunity to turn off room lighting, producing darkness; (2) the opportunity to view a female rat; (3) the opportunity to turn off white noise; (4) the opportunity to drink; (5) the opportunity to eat; and (6) "other," representing time in the hallway between compartments. Each subject underwent a series of conditions characterized as an A-B-A-C-A design. Manipulations consisted of the removal of a low-probability response (darkness) and of a high-probability response (escape from noise) in a counter-balanced manner across subjects. The dependent measure for all subjects was the percentage of total session time spent in each compartment. Four predictive rules concerning the redistribution of behavior after response restriction were tested, including the constant-ratio rule, equal time redistribution, the most probable alternative, and the sequential-dependency rule. The results indicate no support for any of the four predictive rules and suggest that empirical assessment of restriction effects is necessary in reinforcement studies involving temporally extended responses.