Although E bias has been experimentally induced and its effects discussed, few attempts have been made to explain it or to study it when E simultaneously runs all experimental conditions. In this study 27 naive Es conditioned fictitiously typed “bright” and “dull” rats for bar-pressing. Six Es ran only “bright” Ss, 6 Es ran only “dull” Ss, and 15 Es ran both types. The mean differences among groups were not significant, although there was evidence that Es were biased and those who ran both conditions showed attenuated differences. The negative results were attributed to a long pretraining period for Es, and the bias present was explained as an initial and not continuing response to conformity stimuli in an ambiguous situation.
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