The preference-for-signaled-shock phenomenon: Fifty days with scrambled shock in the shuttlebox

Abstract

In humans, recent direct investigations of the preference-for-signaled-shock (PSS) phenomenon in over 500 subjects have failed to confirm the existence of this. phenomenon. In rats, to whom relatively strong sho(~ks (~an he given. the evidence is contradictory. and much of it is methodologically confounded. lIowev(~r. a reeent shuttlehox study which was free of such confoundings ohtained a clear demonstration of PSS in thwe suhjects and suggested that amount of training or experience with the alternatives may he I'ritieal for animal PSS. In the present study. the aim was to increase the amount-of· training variahle extensively and to usc enough suhjects to allow valid statistical assessment of the results. Fourteen rats wer<~ therdore trained for 50 days in a shuttlehox preparation which pitted time spent in a signaled unmodifiahle shoek condition against time spent in unsignaled unmodifiahle shock. No significant group rJr(~feren<~e emerged for the total sample. although individual suhject demonstrations of an orderly prderen<~e for signaled and unsignaled shock were possihle. Accordingly. while amount of training may he important for successful demonstrations of stahle preference for signaled or unsignaled shock. the training variable does not appear to be relevant for determining group PSS. Insofar as group data are concerned, current evidence suggests, then, that, when methodological confoundings are removed, neither humans nor animals should he expected to yield PSS. In fact. new unconfounded evidence in the animal literature. using valid statistical assessment. suggests that under some conditions unsignaled sho(~k is dearly preferred to signaled. inescapable. unmodifiable shock.

Reliability and sources of control of preference for signaled shock

“…Selecting Biederman and Furedy (1976) as representative, we noted that they increased the number of trials in that study from the low values of many of their earlier studies (e.g., Biederman & Furedy, 1973) to a value in excess of that used in most of the reported instances of PSS. Yet a number of potential problems are evident: (1) Their .6-mA, 5.0-sec scrambled footshock [assumed to be unmodifiable based on data of Furedy and Biederman (I 976)] was 10 times the duration and half the intensity used in most of the successful studies [e.g., Badia, Harsh, Coker, and Abbott (I976) used 1.6 mA for .5 sec] .…”

“…These results stand in sharp contrast to Experiment 2, which differed only by not having equal luminosity in the two compartments. Collectively, Experiments 2 and 3 suggest one possible reason for the failure of Biederman and Furedy (1976) to observe a PSS.…”

“…In a more recent critique of the PSS phenomenon, Biederman and Furedy (1976) have questioned the small number of subjects (three) used by Miller et al (1974) while failing to note that each of these subjects met three successive independent criteria. In response to this , criticism concerning group size, we feel that it is appropriate to briefly report arecent study that is a near replication of the experiment of Miller et al (1974).…”

“…The 5-cm-wide opening in the partition between the compartments was without a hurdle so as to avoid providing a shock-free ledge for the animals. Additionally, the previously 6-cm-high black and white strips on the walls of the shuttleboxes were replaced with strips 15 cm in height , the same height as that used by Biederman and Furedy (1976).…”

Does shock modifiability contribute to preference for signaled shock?

“…In spite of these extensive findings, criticism of the fundamental data base has persisted (e.g., Biederman & Furedy, 1973Furedy & Biederman, 1976;Marlin, Berk, & Miller, 1978). A major issue is the degree to which previous findings may be affected by the method used to deliver shock.…”