An experimental analysis of surprise

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Abstract
We investigated the effects of a schema-discrepant event on three characteristics of surprise: delay in the execution of a simple action (measured by reaction times), involuntary focusing of attention toward the surprising stimulus (measured by memory performance), and subjective experience of surprise (measured by the subjects' ratings). The experimental procedure in each of the four experiments reported here was related to a technique introduced by McLeod, Mathews, and Tata (1986). In each trial 2 words were displayed simultaneously, one above the other, on a computer screen (for 3sec). Either together with the onset of the word display or 0.5sec, 1sec, and 2sec later a dot appeared for 0.1sec, either above the upper or below the lower word. Subjects were instructed to respond to the position of the dot by pressing one of two keys. In the experimental groups, in Trials 1–29 both words were presented as black letters on a white ground. This procedure was expected to establish a schema for the mode of presentation of the words. In Trial 30, one of the two words was displayed in an inverted typescript (white letters on black ground). This event was supposed to be schema-discrepant and was expected to elicit surprise. In the control groups, the same event happened. However, in these groups, the event was not schema-discrepant, because in each of the preceding trials one of the two words had been presented in an inverted format. In line with our predictions, the schema-discrepant event led (in the experimental groups) to a delay in the execution of the required action and a subjective experience of surprise. An unexpected memory test, performed immediately after Trial 30, revealed that most of the subjects in the experimental groups recalled the inverted word and the position of the dot in Trial 30, whereas most of the control subjects did not recall the word and the dot's position. These results are discussed in terms of the attentional processes elicited by the schema-discrepant event.