1981 Volume 30 Issue 2 Pages 115-126
WEISS et al. (13) showed that administration of tail shock to two animals in the same apparatus so that they would fight in response to shock caused these animals to develop less severe gastric lesions than animals which received the same shocks while alone.Why did fighting behavior reduce the magnitude of gastric lesions? The most obvious possibility is that fighting behavior functioned as a coping response.The present experiment sought to extend the generality of these phenomenon by examining the effect of the psychological variable of being able to express aggression in response to an electric shock on subsequent Y-maze avoidance and/or escape learning - learned helplessness paradigm - (6) in the rat.The following prediction was tested : the subjects that fought with each other in response to electric shock were faster to aquire in a Y-maze brightness discrimination task to avoid and/or escape electric grid shock when compared with subjects that received the same shock alone so that fighting behavior did not occur.
The preshock conditions are shown schematically in Fig.1.Two subjects together in preshock chamber received shock through their safety pin electrodes, which were wired in series (Fight group, N=12).A subject of Alone group (N=12) in preshock chamber received shock through his safety pin electrode.The sequence of events in the preshock procedure began with presentation of a 2000 Hz, 80db tone.After 5 sec of tone alone, an electric shock was delivered and the tone continued.Shock was 1 mA and lasted for 5 sec.The intertrial interval was a variable interval 60 sec with a range 15-105 sec (64 trials).A subject of Restraint group (N=12) in preshock chamber received no shock but simply remained his chamber for about 70 min.At the end of the 24 hrs homecage resting period, all animals were tested in a discriminated Y-maze avoidance and/or escape task.Trials in the automated Y-maze were programmed on a variable interval 60 sec intertrial interval and consisted of switching the light cue in a random order to one of the previously dark arms.Entry into the lighted arm within 5 sec successfully avoided shock.Failuure to avoid within 5 sec resulted in shock onset after which only escape responses were possible (Fig.2).The following response measures were recorded during Y-maze test : correct avoidance and escape, incorrect avoidance and escape, and failure to escape.
The Alone group escaped as well as Fight group.The Fight group did not differ significantly from the Alone group on number of failures to escape (Table 1).Restraint group had marginally less escape failures, but was significantly faster in latency than its shocked groups-Fight and Alone groups (Fig.3).Mean number trials of correct avoidance and escape, incorrect avoidance and escape, and failures to escape are shown in Fig.4.Pattern of response topography in the discriminated Y-maze avoidance and/or escape test situation was significantly different between the Fight and Alone groups.Mean number of correct escape trials was significantly greater for Fight rats when compared to Alone rats during the 30 test trials.
Since no difference was obtained between the Fight group and Alone group in the mean response latency in the Y-maze, the difference in the number of correct escape can not be interpreted as reflecting differential inescapable shock-induced activity changes (1).Thus discrimination from the present study clearly showed that animals shocked together so that they fought with one another in response to shock did not show interference with discrimination learning in a Y-maze task than did animals shocked alone.