RAPID ACQUISITION OF DISCRETE‐TRIAL LEVER‐PRESS AVOIDANCE: EFFECTS OF SIGNAL‐SHOCK INTERVAL¹

Abstract

Acquisition of discrete-trial lever-press avoidance learning was studied in three experiments. Experiment I compared a new training procedure, which produces rates of leverpress avoidance learning comparable to those obtained in shuttle boxes, with a "conventional", less efficient training procedure. A factorial design was used to compare continuous versus intermittent shock and a long-variable versus a short-fixed signal-shock interval. Learning was best in the groups trained with the long and variable interval and poorest in those trained with the short and fixed interval. Type of shock had no effect. Experiment II separated the effects of duration from those of variability of the signal-shock interval. Fixed and variable intervals of 10 and 60 sec were tested and duration was the only significant factor. Experiment III addressed the effect of the differential opportunity to avoid provided by long signal-shock intervals by varying this interval from 10 to 60 sec in 10-sec steps.Only the 10-sec group showed slow acquisition relative to the others. Analysis of avoidance response latencies showed that the distributions for all groups were positively skewed and that skewness increased with increasing duration of the signal-shock interval. At intervals longer than 20 sec, the animals made progressively less use of their increased opportunity to respond. The data do not support the opportunity-to-respond interpretation of the effects of duration of signal-shock interval and suggest that some type of inhibitory process may block lever-press avoidance learning at intervals as short as 10 sec. The significance of these findings for species-specific defense reaction and preparedness theories was emphasized.

Acquisition of Active Avoidance Behavior as a Precursor to Changes in General Arousal in an Animal Model of PTSD

“…There are various forms of active avoidance that can be modeled in rats, but the desire to track the development of increased avoidant behavior over time led us to adopt distinct lever-press avoidance as our active avoidance procedure. Lever-press avoidance has been utilized for decades to study learning, but it also has a history as a prominent model of anxiety (Pearl, 1963;D'Amato & Fazzaro, 1966;Hurwitz & Dillow, 1968;Gilbert, 1971;Dillow et al, 1972;Berger & Brush, 1975). Derived initially from the 2-factor theory of threat/fear motivation and learned avoidance (Mowrer, 1939a;Mowrer, 1939b;Mowrer & Lamoreaux, 1942;Mowrer & Lamoreaux, 1946), the general premise of this approach is that a learned fear of signals is sufficient to support avoidant behavior without requiring a continued re-exposure to the actual noxious stimulus or event.…”

Opiate Masking of Stress-Induced Hypervigilance: The Cause of Delayed Symptom Presentation in PTSD

“…Lever-press avoidance has been utilized for decades to study learning, but it also has a history as a prominent model of anxiety (Pearl 1963;D'Amato and Fazzaro 1966;Hurwitz and Dillow 1968;Gilbert 1971;Dillow et al 1972;Berger and Brush 1975). Derived initially from the 2-factor theory of threat/fear motivation and learned avoidance (Mowrer 1939a;Mowrer 1939b;Mowrer and Lamoreaux 1942;Mowrer and Lamoreaux 1946), the general premise of this approach is that a learned fear of signals is sufficient to support avoidant behavior without requiring a continued re-exposure to the actual noxious stimulus or event.…”

Free-operant discriminated avoidance in the rat

“…Although this analy sis is not without controversy (see, e .g. , Berger & Brush , 1975), it seems to be a useful theoretical framework for comparing rats with monkeys. Regarding the monkeys , the case can be made that the monkey is a naturally manipulative animal with a great deal of dexterity , for whom barpressing is a prepared response .…”