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Significance and components of the orienting response: effects of signal value versus vigilance
International Elsevier
Journal of Psychophysiology,
343
6 (1988) 343-346
PSP 00209
Significance and components of the orienting response: effects of signal value versus vigilance Robert J. Barry School of Education,
University of New South Wales, Kensington (Accepted
Key words: Preliminary
process
theory;
Orienting
response;
31 March
(Australia)
1988)
Significance;
Vigilance;
Signal value; GSR; Heart rate response
Bernstein et al. (1985) presented the results of an extensive study of the effects of stimulus significance upon electrodennal and heart rate responses. This report examines some of these data from the perspective of preliminary process theory (Barry, 1984b). The categorisation of significance manipulations into prestimulus vigilance and poststimulus signal value outcomes is supported by differential responding in the electrodermal and cardiac measures, as predicted by preliminary process theory.
A recent paper by Bernstein et al. (1985) reported the results of a major study which examined the effects of stimulus significance on a number of physiological indices traditionally associated with the orienting response (OR). Some of the experimental manipulations underlying the extensive data reported there appeared to be relevant to recent theoretical and empirical work carried out in this laboratory on the separation of different aspects of stimulus significance. The present brief report presents a simple analysis of that portion of Bernstein et al.‘s data. The theoretical context for this analysis was provided by two aspects of a recent alternative to Sokolovian unitary OR theory. Preliminary process theory (Barry, 1982, 1984b) accommodates the commonly observed fractionation of physiological responses in the OR context by associating them with a number of sequential preliminary processes which culminate in OR production. The first of these, stimulus registration, involving the
Correspondence: R.J. Barry, School of Education, New South Wales, Kensington 2033, Australia. 0167-8760/88/$03.50
University
0 1988 Elsevier Science Publishers
of
coding of an event’s occurrence, is indexed by a rapid heart rate (HR) deceleration. This is followed by the parallel (but separate) processing of stimulus magnitude and novelty, the outcome of which generates the OR in a mechanistic fashion (Groves and Thompson, 1970). The only clear-cut OR index recognised by preliminary process theory to date is the electrodermal response or GSR. This entire OR production sequence is modulated by stimulus significance, which is treated in the theory as an expression of Maltzman’s (1979) ‘cortical set’ concept. Since preliminary process theory posits a sequential processing of the stimulus, leading finally to the OR, it is apparent that stimulus significance may have differential impact throughout the processing sequence, depending upon the relative timing of its impact. As an example of such timing effects, Barry (1981) drew a distinction between manipulations of prestimulus ‘ vigilance’ and poststimulus ‘signal value’. The former was described as “primarily a function of the prestimulus activity of the subject as he readies himself in anticipation of the stimulus” (Barry, 1981, p. 146), and the latter in terms of “what the subject does after presentation of the stimulus:
B.V. (Biomedical
Division)
344
He emits an RT response, counts the stimulus occurrence, memorizes its elements, etc.” (ibid). The enhancement of signal processing associated with increased significance, together with the sequential nature of OR elicitation, implies that these two aspects of the significance of a particular stimulus will differentially affect HR deceleration and the GSR produced by that stimulus. Experimental manipulations of prestimulus vigilance are predicted to appear in both response indices, and in indices of other preliminary or contingent processes (Barry, 1984b), while manipulations of signal value should change GSR magnitude alone. Supportive data from my laboratory have appeared in Barry (1981, 1982) (signal value manipulation: no effect on HR deceleration) and in Barry and Mitchell (1986) (vigilance manipulation: effect on HR deceleration). Lacey (1967) provides an epitome of the early work relating stimulus significance manipulations to physiological responding. Although this work was performed outside the OR context, it provides a wealth of data which should be accommodated by any OR theory. Two outcomes of this work impinge directly on the present exercise. The first of these concerns the accelerative component of the HR response which immediately follows the initial deceleration discussed above. Studies in my laboratory (Barry 1984a, 1984c, 1986; Barry and Tremayne, 1987) have investigated a number of aspects of this contingent response component, and concluded that the most satisfactory theoretical conception of it is provided by Lacey’s stimulus rejection hypothesis: that the demands of cognitive processing following stimulus onset, established by the situational requirements, are reflected in this component. The second aspect concerns the second deceleration which may then follow the accelerative response component. This was identified by Lacey as associated with preparation for further stimulus intake. Such a preparatory response interleaves with the concept of vigilance discussed above, and should be directly apparent in enhanced cardiac responses to the subsequent stimulus. Bernstein et al. (1985) presented four groups of subjects with 16 trials, each of which consisted of a 21-s 1000 Hz tone at 55 dB, presented to one
ear or the other in an irregular order, followed 9 s later by a visual stimulus (25 mm diameter, 0.4 ft.cd light) of l-s duration. On some trials, a faint click was presented during the 6th or 15th s of the tone. Group ‘BE click’ had to press a pedal immediately after each click, for tones presented to both ears, while group ‘NE’ were not required to respond to any clicks. Two groups, ‘OE click’ and ‘OE delay’, were required to respond to clicks in tones presented to one particular ear (balanced within groups); these groups differed in whether responding was required immediately or at light onset. For the two OE groups, tones to the target ear were designated as the ‘payoff’ condition, while those to the other ear were termed ‘non-payoff’. Electrodermal activity and heart rate data were obtained at l-s intervals throughout each trial, relative to levels immediately before each tone onset. Eyeblink activity was similarly measured in 3-s epochs, but is not considered here. The results of these manipulations may be considered in terms of my vigilance/signal value dichotomy presented above. Tones presented to the target/non-target ears of the OE groups differ in signal value, since evaluation of which ear is stimulated gives information about the necessity for subsequent vigilance regarding occurrence of the target clicks. Prior to stimulus onset, since tones were presented randomly to the two ears, the vigilance level of the subjects relative to the payoff/non-payoff conditions would be expected to be identical. Under such conditions, my theory predicts that significance effects will be apparent in the GSR, but not in the early HR response. GSR and HR responses for the first 5 s of tone presentation are shown in Fig. 1 from the payoff (high signal value) and non-payoff (low signal value) conditions of the two OE groups. Since the latency of the GSR response is about 2 s, the enhanced payoff response was tested by a one-tailed t-test of the difference between corresponding pairs of data points occurring after 2 s. The difference was significant, t = 3.58, df = 2 (P -c 0.05 was adopted as the significance level throughout this report). The HR responses, as expected, consisted of a brief deceleration followed by a brief acceleration; this response form was then followed by the be-
345
b
-2.
5 TIME
L TIME
Csec)
5 “set)
Fig. 1. The effect of signal value on the GSR and HR responses. A: electrodermal data relative to the prestimulus high (HIS) and low (LOS) signal value conditions. B: the corresponding cardiac data.
ginning of a second deceleration. The early onset of this response, and its biphasic nature, required a different test. The hypothesis that significance produces a larger response of the same shape requires that every deviation of the smaller response should be exceeded by the deviation, in the same direction, of the other response. Thus a one-tailed f-test of these signed differences (i.e. taking response direction into account) over 4 data pairs (i.e. excluding the second deceleration) was carried out. This failed to reach statistical significance (t = 1.48, df = 3). Thus, although the GSR reflects signal value, the HR response fails to do so. These data support the prediction derived from preliminary process theory. It is worth noting that, following the initial biphasic HR response, there appears to be a difference in the developing second HR deceleration (reflecting dif-
1.5
A c-l
A
r
I
0
2
1 TIME
Fig. 2. Vigilance
ferent levels of preparation for click occurrence), consonant with the Lacey stimulus intake/ vigilance interpretation offered above. My theory also predicts that manipulations of prestimulus vigilance will be apparent in both indices considered here. The BE and NE groups in the Bernstein et al. study are expected to differ in prestimulus vigilance: BE awaits payoff tones, while NE has no task requirement imposed. Fig. 2 shows data from these groups. Note that both GSRs and HR responses are generally smaller than those shown in Fig. 1, a point which will be returned to later. Tests corresponding to those used above indicated significant differences in both response measures (GSR: t = 4.34, df = 2; HR: t = 3.22, df = 3). Thus, as predicted, the vigilance manipulation is apparent in the initial biphasic HR response, as well as in the GSR. A difference
HiU
1
1
level (0 s) for the
3
4
Hi U
+ 5
TIME
tsec)
effects on the electrodermal and cardiac responses. A: GSR relative to the prestimulus low (LoV) vigilance conditions. B: the corresponding HR data.
level for the high (HiV) and
346
in the second deceleration of the HR response, associated with differential anticipatory preparation for click occurrence, is again apparent in these responses. Although not specifically predicted, the differences is response size evident between Figs. 1 and 2 appear to be compatible with the present theoretical formulation. Because of the greater prestimulus uncertainty associated with the occurrence of target stimuli, the OE groups of Fig. 1 could be expected to be more vigilant than the BE/NE groups of Fig. 2. Analysis of response means of the OE groups versus BE/NE groups (similar to those carried out above) indicated that the HR response difference was significant (t = 2.67, df = 3), while the GSR difference failed to reach significance (t = 2.06, df = 2). However, because these differences were not predicted, the use of the a priori t-test is not strictly applicable, and no great reliance should be placed upon this finding. Differences in the cardiac effects produced by different aspects of stimulus significance, in a context of similar GSR effects, have been demonstrated here. These reflect two aspects of preliminary process theory outlined above: response fractionation, and the distinction between two dimensions of stimulus significance. Although such differences were not examined in the report by Bernstein et al. (1985) it is encouraging that such predicted effects may be found in data collected independently in another laboratory. There is no doubt that significance is a potent variable in the OR context, as has long been claimed by Bernstein. However, this brief report indicates that the concept of stimulus significance needs to be refined beyond the casual level of usage often employed in OR studies. Further, the implicit use of a unitary OR concept, in the face of established response fractionation, may serve to obscure important points in the data. In contrast, preliminary process theory offers a coherent account of response fractionation and a variety of
significance effects, leading to unique predictions of the sort explored here. As this theory also integrates with John Lacey’s work on the fractionation of tonic response measures, and the stimulus intake/rejection hypothesis, it encourages a more detailed exploration of phasic and tonic aspects of the OR. My thanks are due to Alvin S. Bernstein for supplying the group mean data used to generate the figures included here, and to Eugene Galvin for assistance with data analysis and figure preparation. Barry, R.J. (1981) Signal value and preliminary processes in OR elicitation. Paolou. J. Bid. Sci., 16: 144-150. Barry, R.J. (1982) Novelty and significance effects in the fractionation of phasic OR measures: a synthesis with traditional OR theory. Psychophysiology, 19: 28-35. Barry, R.J. (1984a) The evoked cardiac response under processing load. Physiol. Psychol., 12: 35-40. Barry, R.J. (1984b) Preliminary processes in OR elicitation. Acta Psychol., 55: 109-142. Barry, R.J. (1984c) Trials effects in the evoked cardiac response under processing load. Physiol. Psychol., 12: 315-318. Barry, R.J. (1986) Heart rate deceleration to innocuous stimuli: an index of the orienting response or stimulus registration? Physiol. Psychol., 14: 42-48. Barry, R.J. and Mitchell, F.H. (1986) The effect of vigilance upon the evoked cardiac response to simple stimuli. Physiol. Psychol., 14: 141-145. Barry, R.J. and Tremayne, P. (1987) Separation of components in the evoked cardiac response under processing load. J. Psychophysiol, 1: 259-264. Bernstein, AS., Taylor, K.W., Weinstein, E. and Riedel. J. (1985) The effect of stimulus significance on relatively sustained (tonic-like) and relatively transient (phasic-like) aspects of electrodermal, heart rate, and eyeblink response. Biol. Psychol., 21: 183-228. Groves, P.M. and Thompson, R.F. (1970) Habituation: a dual process theory. Psychol. Reu., 77: 419-450. Lacey, J.I. (1967) Somatic response patterning and stress: some revisions of activation theory. In M.H. Appley and R. Trumbull (Eds.), Psychological Stress: Issues in Research, Appleton-Century-Crofts, New York. Maltzman, I. (1979) Orienting reflexes and significance: a reply to O’Gorman. Psychophysiology, 16: 274-282.
Journal of Psychophysiology,
343
6 (1988) 343-346
PSP 00209
Significance and components of the orienting response: effects of signal value versus vigilance Robert J. Barry School of Education,
University of New South Wales, Kensington (Accepted
Key words: Preliminary
process
theory;
Orienting
response;
31 March
(Australia)
1988)
Significance;
Vigilance;
Signal value; GSR; Heart rate response
Bernstein et al. (1985) presented the results of an extensive study of the effects of stimulus significance upon electrodennal and heart rate responses. This report examines some of these data from the perspective of preliminary process theory (Barry, 1984b). The categorisation of significance manipulations into prestimulus vigilance and poststimulus signal value outcomes is supported by differential responding in the electrodermal and cardiac measures, as predicted by preliminary process theory.
A recent paper by Bernstein et al. (1985) reported the results of a major study which examined the effects of stimulus significance on a number of physiological indices traditionally associated with the orienting response (OR). Some of the experimental manipulations underlying the extensive data reported there appeared to be relevant to recent theoretical and empirical work carried out in this laboratory on the separation of different aspects of stimulus significance. The present brief report presents a simple analysis of that portion of Bernstein et al.‘s data. The theoretical context for this analysis was provided by two aspects of a recent alternative to Sokolovian unitary OR theory. Preliminary process theory (Barry, 1982, 1984b) accommodates the commonly observed fractionation of physiological responses in the OR context by associating them with a number of sequential preliminary processes which culminate in OR production. The first of these, stimulus registration, involving the
Correspondence: R.J. Barry, School of Education, New South Wales, Kensington 2033, Australia. 0167-8760/88/$03.50
University
0 1988 Elsevier Science Publishers
of
coding of an event’s occurrence, is indexed by a rapid heart rate (HR) deceleration. This is followed by the parallel (but separate) processing of stimulus magnitude and novelty, the outcome of which generates the OR in a mechanistic fashion (Groves and Thompson, 1970). The only clear-cut OR index recognised by preliminary process theory to date is the electrodermal response or GSR. This entire OR production sequence is modulated by stimulus significance, which is treated in the theory as an expression of Maltzman’s (1979) ‘cortical set’ concept. Since preliminary process theory posits a sequential processing of the stimulus, leading finally to the OR, it is apparent that stimulus significance may have differential impact throughout the processing sequence, depending upon the relative timing of its impact. As an example of such timing effects, Barry (1981) drew a distinction between manipulations of prestimulus ‘ vigilance’ and poststimulus ‘signal value’. The former was described as “primarily a function of the prestimulus activity of the subject as he readies himself in anticipation of the stimulus” (Barry, 1981, p. 146), and the latter in terms of “what the subject does after presentation of the stimulus:
B.V. (Biomedical
Division)
344
He emits an RT response, counts the stimulus occurrence, memorizes its elements, etc.” (ibid). The enhancement of signal processing associated with increased significance, together with the sequential nature of OR elicitation, implies that these two aspects of the significance of a particular stimulus will differentially affect HR deceleration and the GSR produced by that stimulus. Experimental manipulations of prestimulus vigilance are predicted to appear in both response indices, and in indices of other preliminary or contingent processes (Barry, 1984b), while manipulations of signal value should change GSR magnitude alone. Supportive data from my laboratory have appeared in Barry (1981, 1982) (signal value manipulation: no effect on HR deceleration) and in Barry and Mitchell (1986) (vigilance manipulation: effect on HR deceleration). Lacey (1967) provides an epitome of the early work relating stimulus significance manipulations to physiological responding. Although this work was performed outside the OR context, it provides a wealth of data which should be accommodated by any OR theory. Two outcomes of this work impinge directly on the present exercise. The first of these concerns the accelerative component of the HR response which immediately follows the initial deceleration discussed above. Studies in my laboratory (Barry 1984a, 1984c, 1986; Barry and Tremayne, 1987) have investigated a number of aspects of this contingent response component, and concluded that the most satisfactory theoretical conception of it is provided by Lacey’s stimulus rejection hypothesis: that the demands of cognitive processing following stimulus onset, established by the situational requirements, are reflected in this component. The second aspect concerns the second deceleration which may then follow the accelerative response component. This was identified by Lacey as associated with preparation for further stimulus intake. Such a preparatory response interleaves with the concept of vigilance discussed above, and should be directly apparent in enhanced cardiac responses to the subsequent stimulus. Bernstein et al. (1985) presented four groups of subjects with 16 trials, each of which consisted of a 21-s 1000 Hz tone at 55 dB, presented to one
ear or the other in an irregular order, followed 9 s later by a visual stimulus (25 mm diameter, 0.4 ft.cd light) of l-s duration. On some trials, a faint click was presented during the 6th or 15th s of the tone. Group ‘BE click’ had to press a pedal immediately after each click, for tones presented to both ears, while group ‘NE’ were not required to respond to any clicks. Two groups, ‘OE click’ and ‘OE delay’, were required to respond to clicks in tones presented to one particular ear (balanced within groups); these groups differed in whether responding was required immediately or at light onset. For the two OE groups, tones to the target ear were designated as the ‘payoff’ condition, while those to the other ear were termed ‘non-payoff’. Electrodermal activity and heart rate data were obtained at l-s intervals throughout each trial, relative to levels immediately before each tone onset. Eyeblink activity was similarly measured in 3-s epochs, but is not considered here. The results of these manipulations may be considered in terms of my vigilance/signal value dichotomy presented above. Tones presented to the target/non-target ears of the OE groups differ in signal value, since evaluation of which ear is stimulated gives information about the necessity for subsequent vigilance regarding occurrence of the target clicks. Prior to stimulus onset, since tones were presented randomly to the two ears, the vigilance level of the subjects relative to the payoff/non-payoff conditions would be expected to be identical. Under such conditions, my theory predicts that significance effects will be apparent in the GSR, but not in the early HR response. GSR and HR responses for the first 5 s of tone presentation are shown in Fig. 1 from the payoff (high signal value) and non-payoff (low signal value) conditions of the two OE groups. Since the latency of the GSR response is about 2 s, the enhanced payoff response was tested by a one-tailed t-test of the difference between corresponding pairs of data points occurring after 2 s. The difference was significant, t = 3.58, df = 2 (P -c 0.05 was adopted as the significance level throughout this report). The HR responses, as expected, consisted of a brief deceleration followed by a brief acceleration; this response form was then followed by the be-
345
b
-2.
5 TIME
L TIME
Csec)
5 “set)
Fig. 1. The effect of signal value on the GSR and HR responses. A: electrodermal data relative to the prestimulus high (HIS) and low (LOS) signal value conditions. B: the corresponding cardiac data.
ginning of a second deceleration. The early onset of this response, and its biphasic nature, required a different test. The hypothesis that significance produces a larger response of the same shape requires that every deviation of the smaller response should be exceeded by the deviation, in the same direction, of the other response. Thus a one-tailed f-test of these signed differences (i.e. taking response direction into account) over 4 data pairs (i.e. excluding the second deceleration) was carried out. This failed to reach statistical significance (t = 1.48, df = 3). Thus, although the GSR reflects signal value, the HR response fails to do so. These data support the prediction derived from preliminary process theory. It is worth noting that, following the initial biphasic HR response, there appears to be a difference in the developing second HR deceleration (reflecting dif-
1.5
A c-l
A
r
I
0
2
1 TIME
Fig. 2. Vigilance
ferent levels of preparation for click occurrence), consonant with the Lacey stimulus intake/ vigilance interpretation offered above. My theory also predicts that manipulations of prestimulus vigilance will be apparent in both indices considered here. The BE and NE groups in the Bernstein et al. study are expected to differ in prestimulus vigilance: BE awaits payoff tones, while NE has no task requirement imposed. Fig. 2 shows data from these groups. Note that both GSRs and HR responses are generally smaller than those shown in Fig. 1, a point which will be returned to later. Tests corresponding to those used above indicated significant differences in both response measures (GSR: t = 4.34, df = 2; HR: t = 3.22, df = 3). Thus, as predicted, the vigilance manipulation is apparent in the initial biphasic HR response, as well as in the GSR. A difference
HiU
1
1
level (0 s) for the
3
4
Hi U
+ 5
TIME
tsec)
effects on the electrodermal and cardiac responses. A: GSR relative to the prestimulus low (LoV) vigilance conditions. B: the corresponding HR data.
level for the high (HiV) and
346
in the second deceleration of the HR response, associated with differential anticipatory preparation for click occurrence, is again apparent in these responses. Although not specifically predicted, the differences is response size evident between Figs. 1 and 2 appear to be compatible with the present theoretical formulation. Because of the greater prestimulus uncertainty associated with the occurrence of target stimuli, the OE groups of Fig. 1 could be expected to be more vigilant than the BE/NE groups of Fig. 2. Analysis of response means of the OE groups versus BE/NE groups (similar to those carried out above) indicated that the HR response difference was significant (t = 2.67, df = 3), while the GSR difference failed to reach significance (t = 2.06, df = 2). However, because these differences were not predicted, the use of the a priori t-test is not strictly applicable, and no great reliance should be placed upon this finding. Differences in the cardiac effects produced by different aspects of stimulus significance, in a context of similar GSR effects, have been demonstrated here. These reflect two aspects of preliminary process theory outlined above: response fractionation, and the distinction between two dimensions of stimulus significance. Although such differences were not examined in the report by Bernstein et al. (1985) it is encouraging that such predicted effects may be found in data collected independently in another laboratory. There is no doubt that significance is a potent variable in the OR context, as has long been claimed by Bernstein. However, this brief report indicates that the concept of stimulus significance needs to be refined beyond the casual level of usage often employed in OR studies. Further, the implicit use of a unitary OR concept, in the face of established response fractionation, may serve to obscure important points in the data. In contrast, preliminary process theory offers a coherent account of response fractionation and a variety of
significance effects, leading to unique predictions of the sort explored here. As this theory also integrates with John Lacey’s work on the fractionation of tonic response measures, and the stimulus intake/rejection hypothesis, it encourages a more detailed exploration of phasic and tonic aspects of the OR. My thanks are due to Alvin S. Bernstein for supplying the group mean data used to generate the figures included here, and to Eugene Galvin for assistance with data analysis and figure preparation. Barry, R.J. (1981) Signal value and preliminary processes in OR elicitation. Paolou. J. Bid. Sci., 16: 144-150. Barry, R.J. (1982) Novelty and significance effects in the fractionation of phasic OR measures: a synthesis with traditional OR theory. Psychophysiology, 19: 28-35. Barry, R.J. (1984a) The evoked cardiac response under processing load. Physiol. Psychol., 12: 35-40. Barry, R.J. (1984b) Preliminary processes in OR elicitation. Acta Psychol., 55: 109-142. Barry, R.J. (1984c) Trials effects in the evoked cardiac response under processing load. Physiol. Psychol., 12: 315-318. Barry, R.J. (1986) Heart rate deceleration to innocuous stimuli: an index of the orienting response or stimulus registration? Physiol. Psychol., 14: 42-48. Barry, R.J. and Mitchell, F.H. (1986) The effect of vigilance upon the evoked cardiac response to simple stimuli. Physiol. Psychol., 14: 141-145. Barry, R.J. and Tremayne, P. (1987) Separation of components in the evoked cardiac response under processing load. J. Psychophysiol, 1: 259-264. Bernstein, AS., Taylor, K.W., Weinstein, E. and Riedel. J. (1985) The effect of stimulus significance on relatively sustained (tonic-like) and relatively transient (phasic-like) aspects of electrodermal, heart rate, and eyeblink response. Biol. Psychol., 21: 183-228. Groves, P.M. and Thompson, R.F. (1970) Habituation: a dual process theory. Psychol. Reu., 77: 419-450. Lacey, J.I. (1967) Somatic response patterning and stress: some revisions of activation theory. In M.H. Appley and R. Trumbull (Eds.), Psychological Stress: Issues in Research, Appleton-Century-Crofts, New York. Maltzman, I. (1979) Orienting reflexes and significance: a reply to O’Gorman. Psychophysiology, 16: 274-282.