The human orienting reflex : an investigation of the role of context

Recent theories of habituation can be differentiated by whether or not they include a process allowing a comparison between incoming information and stored representations. Predictions concerned with the effects of stimulus intensity, interstimulus interval, the number of stimulus presentations, and stimulus omission were derived from three representational theories (Óman, 1979; Sokolov, 1960, 1963; Wagner, 1976, 1978,), and one non-representational theory (Groves & Thompson, 1970), and compared with data from previous research. Although this review failed to offer differential support to any one of these theories, it was suggested that results from studies which examined stimulus omission and stimulus predictability supported the associative theories proposed by Wagner (1976, 1978) and Óman (1979). This thesis is therefore concerned with an examination of these two theories. Wagner and Óman accorded contextual cues a crucial role in their information-processing models of habituation. The response to an incoming stimulus was assumed to depend upon the degree to which short-term memory was `primed' with its representation. Priming was said to be triggered by a recent stimulus presentation (lq`self-generated priming'), or by the presentation of contextual cues with which stimulus was associated (lq`retrieval-generated priming'). According to Wagner and Óman, long-term habituation was context-dependant: therefore, various manipulations of the environment should influence observed responding. Six experiments are reported which examine the effects of three different contextual manipulations on long-term habituation of electrodermal orienting response. In Experiments 1-3, various aspects of the experimental context were either changed (experimental group) or held constant (control group) between two series of stimulus presentation trials. Extinction of the relationship between the target stimulus and the environmental context was manipulated in Experiment 4 by either removing the subject from the room during an intersession interval (control group) or leaving him/her in the experimental chamber (experimental group). In Experiments 5 and 6, reliable intra-session cues for the target stimulus were established. The contextual manipulation involved either changing the intra-session cues (experimental group) or holding them constant (control group) between experimental sessions. The data provided consistant evidence of long-term habituation, but there was little evidence to suggest that this was contextually-mediated.The important influence of verbal behavior in both Pavlovian and operant conditioning has been highlighted in a number of recent papers. Thus, in conclusion, it is suggested that further research might employ individual subject protocols in order to examine the relationship between verbal behaviour and physiological responses. (D72457/87)