Date of Award


Degree Name

Master of Arts



Access Setting

Masters Thesis-Open Access


Rats were trained on an unsignalled shock procedure, using a two lever apparatus. Responses on one lever postponed the onset of electric shock for a specified time period, the Avoidance-Shock interval. A response on the second lever terminated shock and delayed the onset of the next shock eight seconds, the Escape-Shock interval. Shock was continuous until the subject depressed the second lever. Changes in response rate on both levers were recorded as a function of manipulations of the duration of the Avoidance-Shock interval.

If responses on both bars are summed, data obtained are comparable with findings obtained from the manipulation of R-S intervals in a traditional free operant avoidance procedure. When response rates obtained from each lever are considered separately this similarity is less evident.