The orienting response as novelty and significance detector: reply to O'Gorman.

O'Goiman's (1979) criticisms of the orienting response (OR) significance hypothesis are not well-founded. The hypothesis is not based solely on electrodermal data—studies reporting significance effects for heart rate and pupillary OR are cited. The hypothesis does not discard novelty but suggests that an interaction between uncertainty and significance triggers OR. Differential reactivity across OR components reflects stimulus- and individual-response factors, and does not require separate “significance registers.” Since the hypothesis specifically maintains that appraisals of stimulus significance affect the OR, not the mere fact of cognitive appraisal per se, no general “cognitive appraisal effect” was ever expected. O'Gorman confuses the difficulty of estimating the subject's spontaneous judgments of significance with the relative ease of manipulating significance in the laboratory. He considers classic OR theory more “objective” only because he fails to look closely enough at the complex judgmental processes involved in stimulus intake, model building, and matching functions. O'Gorman's contentions of different initial- and test-ORs, and of a simple additive relationship between significance and OR, lack supportive data and are challenged by available evidence. Literature is cited suggesting that: a) scanning is continuously biased toward the detection of significant stimuli; b) detection of a sgnificant stimulus feature triggers increased information scanning, increasing the possibility that previously unrecognized uncertainty will be detected, and c) lowers the criterion level of the OR “threshold,” increasing the likelihood of OR if uncertainty is detected. Evidence is cited suggesting that the significance-OR, and perhaps attention in general, is mediated by neocortical-limbic interaction, the limbic' “motivational” evaluator of stimulus input steering and switching neocortical “intellectual” analyzers of stimulus pattern.