Effects of arousal on attention to central and peripheral visual stimuli

Acta Psychologica North-Holland

157

66 (1987). 157-172

EFFECTS OF AROUSAL ON ATTENTION AND PERIPHERAL VISUAL STIMULI * Kimron

L. SHAPIRO

Unrvers~t_vof Caigaar?;. Calgay;, Accepted

and Thomas

TO CENTRAL

L. JOHNSON

Canada

July 1987

Human attention research has demonstrated that vision dominates attention when vision is competing against audition under normal conditions, but that audition dominates attention under conditions of arousal set by electric shock. Two experiments were conducted to determine whether an attentional switching mechanism exists between the central and peripheral visual systems similar to that which exists between the visual and auditory modalities. In experiment 1, increasing subject’s level of arousal by administering brief electric shocks resulted in attenuated central visual dominance of attention with a predictably located central stimulus and a randomly located peripheral stimulus. In experiment 2, where locations of both peripheral and central stimuli were unpredictable, peripheral visual dominance was observed in the aroused subjects. Non-aroused control groups in both experiments demonstrated central visual dominance. The results are discussed in terms of the adaptive significance of attentional switching mechanisms.

The human visual system repeatedly has been shown to dominate attention when this system competes for attention with audition (Colavita 1974; Colavita and Weisburg 1979: Egeth and Sager 1977) with proprioception (Pick et al. 1969), and with taction (Gibson 1933; Rock and Victor 1964). Various investigators have been largely unsuccessful in finding a means by which to attenuate visual dominance (e.g., Colavita and Weisburg 1979; Egeth and Sager 1977). Recently Shapiro et al. (1984) demonstrated that, while attention normally may be directed to the visual modality, attention can be shifted to the auditory modality under conditions of aversive arousal established by delivering mild, unpredictable electric shocks to a subject’s finger. This finding * The authors wish to thank Dr. Raymond Klein for his insightful comments during the preparation of this manuscript, as well as Dr. Jane Raymond for her valuable advice concerning the vision theory underlying these experiments. Geoff Smith and Derek Lin are thanked for their considerable efforts in programming the experiments reported here. Requests for reprints should be sent to K.L. Shapiro, Dept. of Psychology, University of Calgary, 2500 University Drive N.W., Calgary, Alberta, Canada T2N 1N4.

OOOl-6918/87/$3.50

0 1987, Elsevier Science Publishers

B.V. (North-Holland)

158

K. L. Shapiro, T. L. Johnson / Effects of urousul on attentmn

has been useful in linking human to animal research, since similar results have been found with both classical and operant conditioning paradigms involving animals as subjects (e.g., Foree and LoLordo 1973; Randich et al. 1978; Shapiro et al. 1980). The results of these experiments suggest that attention is directed under conditions of normal arousal to visual stimuli but under conditions of heightened arousal to auditory stimuli. On the basis of similar findings in a series of experiments investigating associative constraints in animal learning, Shapiro et al. (1980) suggested that many species may be visually ‘dominant’ under normal (non-arousal) conditions, since much biologically important information (e.g., for food localization) is received via the visual modality. On the other hand, the same species may ‘switch’ to attend auditory stimulation when in an aroused state in order to detect potential threats (e.g., predators) rapidly. Such auditory dominance may serve the function of enhancing the detection of threats as a result of the auditory system’s 360” detection capability relative to the visual system’s more restricted, line-of-sight detection properties. Consistent with the notion of attentional switching is the theory advanced by Posner et al. (1976). These investigators suggested a non-sensory (attentional) account of visual dominance based on the idea that vision has a poor alerting capability relative to audition. According to this account, an attention bias to vision results from an effort to compensate for such a visual deficit (see also Klein 1977). Since Posner et al. examined attention in the normal (non-aroused) state, their results may be compared with those of the non-arousal group in Shapiro et al. (1984). Such interpretations of attention suggest that attention may change from one sensory modality to another, depending on which modality best serves an organism’s needs at a given time. Similarly, one might reasonably expect to see shifts of attention between two different functional systems within a particular sensory modality as motivational state is changed. The present series of experiments was designed to examine this possibility within the visual modality.

Experiment

1

The first experiment examined central vs. peripheral visual dominance where the central visual stimulus appeared at the fixation point, whereas

in a situation the peripheral

K. L. Shapiro, T.L. Johnson / Effects of arousal on attention

159

visual stimulus appeared at random locations in the periphery of the visual field. The basic methodology employed by Shapiro et al. (1984) was followed. Method Subjects The subjects were 30 right-handed undergraduate students between the ages of 18 and 22 who were recruited from an introductory Psychology class. No subject had a known visual or hearing impairment which was uncorrected. The subjects were randomly assigned either to the Arousal or Non-Arousal treatment groups. Apparatus An Apple IIe microcomputer was used to control stimulus presentation and record response choice and RT (to the nearest millisecond) on each trial. An Apple III green phosphor monitor with a diffraction filter placed over the screen was used to present the visual stimuli. Both the central and peripheral visual stimuli were green circular fields, subtending a visual angle of l.l” with a luminance of 27.2 cd/m*. A small, dim fixation spot appeared in the center of the screen and remained on throughout the experiment. The central visual stimulus appeared superimposed over the fixation spot in the center of the visual field. The peripheral visual stimulus could appear in any location on the circumference of an imaginary circle with a radius of 7.1 cm (11.5 o ) centered on the fixation point. Electric shocks were delivered by a Grason-Stadler shock generator to the left index finger via two small silver electrodes held in place with an elastic band. Shock duration was programmed at 0.5 set, with shock intensity set individually by each subject. The subject’s head rested on a chin rest 35 cm from the monitor screen and directly in front of and level with the position of the central visual stimulus. The subject responded to either the central or peripheral visual stimulus by depressing one of two respectively, which were mounted on a buttons marked ‘central’ and ‘peripheral’, wooden response panel. The response buttons were accessed by the subject using the index and middle fingers of the right hand. Since the peripheral stimulus could appear in any location around the central stimulus as described above, no attempt was made to counterbalance subjects with regard to the placement of the response buttons. The stimulus terminated as soon as any response was made. If no response occurred within 1000 msec, the stimulus was terminated automatically.

Procedure Subjects were assigned either to the Arousal (shock) or Non-Arousal (control) treatment group. Before the experiment began, each subject in the Arousal group set the shock level according to the instruction that the shock be ‘aversive, but not painful’. The experimenter began by delivering the lowest intensity shock to the subject and proceeded to higher intensities until the subject agreed that the suggested criterion had been reached.

160

K. L. Shaprro, T L. Johnson

/ Effects

of arousalon attention

Subjects in both groups were presented with a series of 100 RT trials and were instructed to maintain their gaze on the fixation spot at all times. On 80 of these trials, either the central or the peripheral visual stimulus alone was presented in a randomly predetermined sequence (single-stimulus trials). The remaining 20 trials were combined central-peripheral trials in which the two stimuli were presented simultaneously (dual trials). Dual trials were randomly interspersed throughout the test sequence with the restriction that no dual trials occur in succession. The subjects were instructed to respond to the appearance of the central or peripheral stimulus on each trial by pressing the appropriate response key as quickly as possible without making mistakes. They were instructed to respond on the key corresponding to the stimulus they detected first on dual trials. Subjects in the Arousal group received instructions identical to those just described and were also informed that they would receive an electric shock immediately after responding on an infrequent number of trials. No other explanation for the shocks was offered. These subjects received a shock immediately following their response on a randomly predetermined 20% of the 80 single-stimulus trials. Subjects were never shocked on dual trials and were shocked on an equal number of central and peripheral single-stimulus trials. All shocks occurred in the identical sequence for all subjects in the Arousal group. Results

Choice responses on dual trials and RTs on both single-stimulus and dual trials for both the Non-Arousal and Arousal groups constituted the variables of interest. Group mean response percentages to both central and peripheral stimuli on dual trials were calculated. Additionally, for each group, mean RTs for central and peripheral responses on both single and dual trials were computed. The intensities of the shock set by all subjects in the Arousal group were so highly similar as to not warrant any statistical consideration. Mean percent responses to the central stimulus in the Non-Arousal condition (M = 71.5%) were significantly different than mean percent responses to the same stimulus in the Arousal group (M = 53.1%; t(28) = 2.93, p -C 0.01). Group mean percent responses on dual trials to central and peripheral stimuli for both the NonArousal and Arousal groups are shown in fig. 1. A t-test revealed that the Non-Arousal group responded to the central stimulus at a level significantly greater than that predicted by chance alone (M = 71.5%; t(28) = 6.05, p < 0.01). suggesting a dominance of central over peripheral responses. The Arousal group, on the other hand, responded to the central stimulus at a level not significantly different than chance, (M = 53.1%, p > 0.05). suggesting no dominance in responses of one stimulus over the other. In the Non-Arousal group, 11 of the 15 subjects responded to the central stimulus on between 65% and 100% of the dual trials, indicating a strong central visual dominance. The remaining four subjects responded to the central stimulus on between 36% and 64% of the dual trials, indicating no strong preference for either the central or peripheral stimulus. No subject in the Non-Arousal group showed a clear preference for the peripheral stimulus.

K. L. Shapiro, T. L. Johnson / Effects of arousal on attention

Non-Arousal

161

Arousal

Group Fig. 1. Percent responding to the central and peripheral stimuli on dual trials in experiment

1.

In contrast to the Non-Arousal group, only five of the 15 subjects in the Arousal group responded to the central stimulus on between 65% and 100% of the dual trials, indicating that fewer subjects had a strong central dominance. Of the remaining subjects, eight responded to the central stimulus on between 36% and 64% of dual trials (indicating no strong central or peripheral preference), while two responded to the central stimulus on between 0% and 35% of the dual trials, indicating a strong peripheral visual dominance. An ANOVA of mean RT for Groups (Non-Arousal vs. Arousal), Trial Type (Single vs. Dual), and Location of the stimulus to which the subject responded (Central vs. Peripheral) was computed. Turning first to the main effects, there was a significant main effect found for Trial Type, F(1,28) = 78.77, p < 0.01. Moreover, there was significant Trial Type by Location interaction, F&28) = 13.42, p < 0.01. Finally, a Groups by Trial Type by Location interaction was found, F&28) = 7.89, p < 0.01. Mean RTs for each of these groups according to Trial Type and Location can be seen in fig. 2. A series of post-hoc tests (Duncan’s method) were performed on the mean RT data. Only those RT patterns which bear on certain theoretical models discussed later (see General discussion) are presented. Turning first to the single-stimulus trials, mean RT to the central stimulus in the Non-Arousal group was faster than mean RT to the peripheral stimulus in the same group, though non-significantly. The same comparison in the Arousal group reveals a significant difference (t(28) = 4.25, p < 0.05) in the direction of a faster mean RT to the central stimulus. Turning now to the dual trials, mean RT to the central stimulus in the Non-Arousal group was faster (though non-significantly) than to the corresponding peripheral stimulus. In the Arousal group, mean RT to the peripheral stimulus was significantly faster than to the central stimulus in the same group (t(28) = 4.92, p < 0.05). Finally, there is a pronounced dual-stimulus interference (32-155 msec) for both central and peripheral stimuli in both the Non-Arousal and Arousal groups as revealed in RTs on dual- as compared to single-stimulus trials. That is, mean RTs on dual trials

162

K. L. Shapiro, T. L. Johnson / Effects of arousal on atlention

c

P Single

c P Dual

Non-Arousal

c

P Single

c P Dual

Arousal

Fig. 2. Mean RTs according to Trial Type, Location and Group in experiment 1

for a chosen stimulus were slower than mean RTs to the corresponding stimulus on single-stimulus trials (p < 0.05). The one exception to this is the comparison between mean RT on single- and dual-stimulus trials to the peripheral stimulus in the Arousal group for which there was no significant difference.

Discussion

In the choice response data of this experiment, there was a clear dominance of central vision over peripheral vision in the Non-Arousal condition. Moreover, there was a lack of significant central dominance in the Arousal group. Although there was no significant peripheral dominance revealed in the Arousal condition, an attenuation of dominance relative to the Non-Arousal group is important in demonstrating that the arousal manipulation exerted a significant effect in directing attention away from the central stimulus. The pattern of results in experiment 1 is similar to that obtained in previous cross-modality experiments (Shapiro et al. 1984: experiment 2) and is consistent with the view that distribution of attention within the visual modality is determined partly by the motivational state of the organism. RT data from dual-stimulus trials in experiment 1 tends to corroborate the choice data just described. Mean RT to the central stimulus when it was chosen on dual trials was faster than mean RT to the peripheral stimulus in the Non-Arousal group, but slower than mean responses to the peripheral stimulus in the group receiving the arousal manipulation. The dual-trial interference noted above also seems to corroborate the hypothesis concerning the effect of shock arousal on attention. Whereas the Non-Arousal group reacted 126 msec later to the peripheral stimulus in dual- as opposed to single-stimulus trials, subjects in the Arousal group exhibited a difference of only 32 msec between these same two conditions. RT data from single-stimulus trials are dealt with in the General discussion since they bear on larger theoretical issues.

K.L. Shapiro, T.L. Johnson / Effecis of arousal on attention

163

It is conceivable that the difference in predictability of the central and peripheral stimuli in experiment 1 may have biased subjects’ attention for the purpose of detection towards one or the other of these two stimulus locations. Accordingly, this might yield only an attenuation of the central dominance effect in the Arousal group, as opposed to a reversal of dominance similar to that seen in the cross-modality experiments of Shapiro et al. (1984: experiment 1). Therefore, a second experiment was conducted in which the locations of both the central and the peripheral stimuli were unpredictable.

Experiment

2

Experiment 2 investigated the notion that predictability of stimulus location is a significant factor in the relationship between arousal and attentional dominance within the visual system. Thus in experiment 2 both the central and peripheral visual stimuli were programmed to appear in unpredictable locations. Method Subjects Subjects were 20 right-handed undergraduates who were naive to the purpose present experiment. They were recruited as in experiment 1.

of the

Apparatus The apparatus, instructions, and procedures were identical to those in experiment 1, except that the central visual stimulus was programmed to appear in any position distributed symmetrically at a distance of 1.7 cm (2.8”) from the fixation point. This ensured that the central stimulus would fall within the parafoveal region of the visual field, as long as gaze remained on the fixation point. ’ The peripheral stimuli also appeared at unpredictable locations, as in experiment 1. All stimulus presentation and response parameters were the same as in experiment 1. Procedure Subjects were randomly assigned to either the Arousal or Non-Arousal treatment group. Subjects in the Arousal group set the shock level according to the same instructions and procedure as in experiment 1. Subjects in both groups were presented with the same series of 100 RT trials, as previously described. The relative composition of single- and dual-stimulus trials 1 The parafoveal visual field, which is similar to the fovea1 visual field in most respects, is bounded by a region of up to approximately 5 o into the visual periphery (Pirenne 1967). Of more importance than the location of the vague boundary between these two areas of the central visual field is our investigation of ‘central’ vs. ‘peripheral’ dominance. Accordingly, it is of lesser importance that precise fovea1 vision is not being examined. In fact, the use of the parafoveal field allows a wider generalization of our results to actual situations where stimuli requiring immediate attention do not necessarily land directly on the fovea.

164

K.L. Shapm,

T.L. Johnson / Effects of arousal on attention

presented to the subject in experiment 2 was the same as in the previous experiment. During this series of trials, subjects were instructed, as before, to respond on the appropriate response key as quickly as possible without making mistakes and to maintain fixation at all times. On dual trials the instructions were again to respond on the key corresponding to the stimulus first detected. Subjects in the Arousal group received identical instructions to those just described and were treated in all respects like Arousal group subjects in experiment 1. These subjects received a shock immediately following their response on a randomly predetermined 20% of the 80 single-stimulus trials. Subjects were never shocked on dual trials and were shocked on an equal number of central and peripheral trials.

Results

As in experiment 1, all RTs and the stimulus (central or peripheral) chosen on dual trials were recorded for subjects in both conditions. Stimulus choice on dual trials and RT to each trial type for both the Non-Arousal and Arousal groups constituted the variables of interest. Group mean central and peripheral RTs on all trials were computed as well as percent responses to both central and peripheral stimuli on dual trials. Mean percent responses to the central stimulus in the Non-Arousal condition (M = 71.4%) were significantly different than mean percent responses to the same stimulus in the Arousal group (M = 39.5%; t(18) = 5.28, p < 0.01). Group mean percent responses on dual trials to central and peripheral stimuli for both the NonArousal and Arousal groups are shown in fig. 3. A r-test revealed that the Non-Arousal group responded to the central stimulus at a level significantly greater than that predicted by chance (M = 71.4%; ~(28) = 5.15, p < 0.01) suggesting a dominance of central over peripheral responses. The Arousal group, on the other hand, responded to the central stimulus at a level significantly less

Non-Arousal

Arousal

Group Fig. 3. Percent responding to the central and peripheral stimuli on dual trials in experiment

2.

165

K. L. Shapiro, T. L. Johnson / Effects of arousal on attention

than chance (M = 39.5%, t(18) = 2.17, p < 0.05) suggesting a dominance of peripheral over central responses. In the Non-Arousal group, six of the ten subjects responded to the central stimulus on between 65% and 100% of the dual trials, indicating a strong central visual dominance. The four remaining subjects responded to central stimulus on between 36% and 64% of the dual trials, indicating no strong preference for either the central or peripheral stimulus. In contrast to the Non-Arousal group, none of the subjects in the Arousal group responded to the central stimulus on between 65% and 100% of the dual trials, indicating that no subject had a strong central dominance. Five of the ten subjects responded to the central stimulus on between 36% and 64% of dual trials, indicating no strong central or peripheral preference, while the other five subjects responded to the central stimulus on between 0% and 35% of the dual trials, indicating a strong peripherul visual dominance. An ANOVA of mean RT for Groups (Non-Arousal vs. Arousal), Trial Type (Single vs. Dual), and Location of stimulus to which the subject responded (Central vs. Peripheral) was computed. The only significant effects were for Trial Type, F(1,18) = 30.10, p < 0.01 and for the Trial Type by Location interaction, F(1,18) = 4.75, p < 0.05. The significant interaction indicates that responses on dual trials were always slower than responses on single-stimulus trials and that this pattern differs slightly for central as opposed to peripheral stimuli. These results are consistent with the pattern reported for experiment 1. Mean RTs for each of these groups according to Trial-Type and Location can be seen in fig. 4. In order to assess the notion discussed above concerning the interaction between stimulus predictability and arousal, choice responding in the arousal groups in experiments 1 and 2 were statistically compared. (Non-Arousal group means in these same experiments were exactly the same.) Percent responses to the central stimulus in the Arousal condition in experiment 1 (M = 53.1%) was significantly different than re-

600

Ia

400

200

c

P

Single

c Dual

Non-Arousal

P

c

P

Single

c

P

Dual

Arousal

Fig. 4. Mean RTs according to Trial Type, Location and Group

in experiment

2.

166

K.L. Shapiro. T. L. Johnson / Effects

sponses to the same stimulus t(23) = 1.81, p < 0.05).

in the same

ofarousal on attention

condition

in experiment

2 (M = 39.5%:

Discussion In this experiment, strong central visual dominance was again observed in the Non-Arousal condition, but peripheral dominance was exhibited by the Arousal group. This finding is in accord with previous research using human subjects (Shapiro et al. 1984) and animal subjects (Shapiro et al. 1980) where attention to the auditory modality was increased with a similar arousal manipulation. The present results also reinforce the notion that predictability of stimulus location is an important factor in determining the distribution of attention within the visual modality (see General discussion for further consideration of this issue). As in experiment 1, the pattern of RT data from the dual-stimulus condition corroborates the data from the choice dependent variable described above, although statistical considerations preclude the confirmation of such a statement. Furthermore, the pattern of data from the single-stimulus trials (with the single exception of mean RT to the central stimulus in the Arousal group) and the finding of a dual-stimulus interference virtually are identical to those reported for experiment 1.

General

discussion

The results of the present experiments suggest that an attentional mechanism operates within the visual modality which is similar to the mechanism which determines dominance relations in the detection of simultaneously presented auditory and visual stimuli. Moreover, the distribution of attention to the central vs. peripheral visual fields was shown to be a function of the interaction between a characteristic of the stimulus (predictability of location) and a motivational state of the subject (arousal). Before discussing the implications of the choice data, we will first present an interpretation of the RT data. Whether an ‘early selection’ model (e.g., Broadbent 1957) or a ‘late selection’ model of attention (e.g., Deutsch and Deutsch 1963; Norman 1968) receives support must be based on RT data taken from single-stimulus trials. ‘Early selection’ models suggest that stimulus selection occurs early in processing and subsequently determines which stimulus is available for potential response output at some later stage. Such a horse race model predicts that choice on dual trials is determined by the relative arrival times of the central and peripheral stimuli.

K. L. Shapiro, T. L. Johnson / Effects of arousal on attention

161

The most salient aspect of the RT data is that single-stimulus RT is significantly faster than dual-stimulus RT. While it seems natural to suppose that this difference is due to response competition, comparison with our previous work makes this interpretation unlikely. In that study dual auditory and visual trials had the same latencies as single-stimulus trials. Since the response demands in that study were equivalent to those here, it is likely that the single vs. dual difference in the present experiments is due to processes prior to response selection. A prime candidate is reciprocal interference in the encoding of two simultaneous stimuli in the visual modality. Physiological considerations suggest that central and peripheral visual channels may interact in this way, although different modalities like auditory and visual are regarded as much more independent. The finding that the dual-single difference is absent in the arousal condition when peripheral stimuli are chosen may be accounted for by the post-hoc assumption that arousal decreases the central channel’s interference upon the peripheral channel. Further studies would be necessary to support this assumption. In any case our main interest is in what stimuli are selected in the Arousal and Non-Arousal dual trial conditions. In any event, since the choice is not due to arrival times as indicated by the lack of a relationship between single central and peripheral RTs and choice responding, we must look to attentional or ‘late selection’ mechanisms for an appropriate explanation. Comparing the results of the dual-stimulus choice data from experiments 1 and 2 addresses the importance of the predictability of stimulus location on attentional dominance. Between these two experiments, a progressively greater effect of shock arousal was revealed. * In experiment 1, where peripheral stimulus location was unpredictable but the central stimulus remained predictable, central dominance was exhibited in the Non-Arousal group with an attenuation of central dominance in the Arousal group. However, in experiment 2, where locations of both stimuli were unpredictable, the arousal manipulation 2 A potential criticism of the arousal manipulation concerns a lack of convergent evidence that the shock manipulation did indeed create a state of arousal. While it is natural to assume that some form of arousal is likely to result from such a manipulation, the exact nature of that arousal is less important than the general conclusion that the shock manipulation does cause a switch in attention away from normally occurring central visual dominance. Whereas it is important for future studies to determine the exact nature of the arousal produced by infrequent electric shock to a subject’s finger, it is beyond the scope of the present research to do so.

16X

K. L. Shapiro, T. L. Johnson / Effects of arousal on attention

produced an actual reversal of dominance so that the peripheral stimulus dominated choice responding in the Arousal group. We suggest that stimulus predictability may affect detection of visual stimuli by affecting the distribution of attention to regions of the visual field independently of gaze direction. In both experiments 1 and 2 the subjects were required to ‘center’ their field of attention on the designated fixation dot. Under these conditions, the arousal manipulation resulted in an expansion of attention to the peripheral region. That arousal produced peripheral dominance in the second experiment, but only an attenuation of central dominance in experiment 1, may have been due to a bias toward one or the other of the two stimuli in the first experiment. For example, because the central stimulus appeared predictably in the same location as the fixation dot, it may have created a condition whereby this stimulus was difficult to ignore in both the Arousal and Non-Arousal conditions. Thus the arousal manipulation was only partially effective in increasing attention to the periphery in experiment 1. It is important to note a potential criticism which may be leveled at the data from these two experiments, before turning to a discussion of various theoretical models on which these data bear. First, it could be argued that, despite instructions to the subject to foveate the fixation point at all times during the experiment, eye movements stemming from a failure to adhere to this instruction may account for the pattern of data previously discussed. That is, the arousal manipulation may direct eye movements to the periphery which in turn predispose responding to that region of visual space. Such a strategy is unlikely since the location of the peripheral stimulus in both experiments 1 and 2 is unpredictable and subjects would not maximize the likelihood of detection with such a strategy. Moreover, such a strategy would have the effect of making most peripheral locations even more peripheral and thus not likely yield the obtained pattern of results. In order to create an unpredictable central stimulus location in experiment 2 we chose to place the central stimulus approximately 3” into the visual periphery. Although it cannot be disputed that this location removes the stimulus from the precise point of foveation, the difference observed between the two groups does suggest the more important conclusion that attention shifts between visual ‘center’ and visual ‘periphery’ as a function of the arousal manipulation. The effects of arousal on allocation of attention to different sense

K. L. Shapiro, T.L. Johnson / Effects of arousal on attention

169

modalities, and to different spatial regions within a modality, are perhaps best understood in terms of the functional role each system plays in various environmental circumstances. A number of researchers (e.g., Bahrick et al. 1954; Bursill 1958; Easterbrook 1959; Hockey 1970a,b; and Wachtel 1968) have found evidence of a reduction in peripheral cue utilization rather than an expansion of attention to peripheral stimuli under conditions of arousal as in the present experiments. Cornsweet (1969), on the other hand, reported an increase in attention to peripheral cues in an arousal condition set by electric shock, a result which is consistent with those of the present series of experiments. According to Cornsweet and others (e.g., Hockey 197Oc, 1979), peripheral cue utilization will increase or decrease as a function of (1) the relationship of the peripheral task to the central task, and (2) the nature of the arousing stimulus. Relative to the first point, Cornsweet’s analysis of various research paradigms concluded that a peripheral task which was unrelated to central task performance (e.g., a motor performance central task in conjunction with a visual stimulus rapid-detection peripheral task) caused subjects’ decreased use of peripheral cues. With regard to the second point, Hockey (197Oc, 1979) suggested that certain forms of arousing stimulation, e.g., noise, will interact with primary or secondary cues to either increase or decrease the selectivity of attention. Hockey suggested that noise as an arousing stimulus may increase attention to peripheral cues in a cognitively complex situation but decrease attention to such cues in a less cognitively complex situation. Various other forms of arousal, e.g., sleep loss, may be expected to have similar or different effects on peripheral cue utilization depending on the nature of the particular arousing stimulus under consideration. In the present series of experiments, central and peripheral task requirements are highly related since they both are part of a rapid visual detection task. Thus on the basis of the above rationale one would predict an increase in attention to peripheral cues in the arousal condition. Moreover, the nature of the arousing stimulus also might be expected to increase attention to the periphery as a function of its evolutionary significance. There is evidence of sensory processing differences between the central (fovea1 or parafoveal) and the peripheral visual systems which is consistent with their proposed functional separateness (e.g., Sagi and Julesz 1985). The peripheral visual system may

170

K. L. Shaprro, T. L. Johnson / Effect.7 of arousal on attention

be viewed primarily as a detection, localization, and orientation mechanism which complements the auditory system in these functions. The central visual system, on the other hand, clearly plays the major role in detailed pattern analysis and recognition (Held 1970). Based on these considerations, it seems reasonable that attention should be directed to the central region of the visual field under normal (non-aroused) conditions for the purpose of maximum stimulus recognition. Under conditions of arousal, however, we anticipated a switch in attention to the visual periphery in order to maximize detection of potentially important information. Shapiro et al. (1984) demonstrated that while the visual system dominates attention under normal circumstances (cf. Colavita 1974; Colavita and Weisburg 1979; Egeth and Sager 1977), the auditory system comes to dominate attention under conditions of arousal. Such a reversal of normal sensory dominance was argued to have an evolutionarily adaptive function, i.e., the chosen stimulus is selected in an effort to maximize stimulus detection. In a fear situation (e.g., predator-prey interaction), locating a source of stimulation and responding quickly are probably more imperative than recognizing the source. The auditory system, therefore, would be the more adaptive system to perform this function, given its 360” detection capability. In non-fear situations (e.g., food-getting), recognizing a source of stimulation would likely be more important than merely localizing the same source. In this case, the visual system would be the better system to rely upon, given its limited detection range but superior discrimination ability. Thus, when audition and vision compete for attention under certain conditions of arousal, the auditory system takes precedence simply because it is a better system for that particular function. The above arguments may be extended in light of the experiments reported in the present paper. The results of the two experiments reported here suggest that a similar two-channel switching mechanism exists within the visual modality as exists between the visual and auditory modalities. We suggest that the function of the peripheral visual system is analogous to that of the auditory system. That is, the peripheral visual system is responsible primarily for rapid detection and localization. Moreover, the interactions between the peripheral and the central visual systems under different motivational states appear to be similar to the interactions between the central visual system and the auditory system. Thus attentional dominance within vision is clearly

K. L. Shapiro, T. L. Johnson / Effects

111

ofarousal onattention

not ‘hard-wired’, but changes as a function the organism by the environment.

of the demands

placed

on

References Bahrick, H.P., P.M. Fitts and R.E. Rankin, 1954. Effects of incentives on reactions to peripheral stimuli. Journal of Experimental Psychology 44, 400-406. Broadbent, D.E., 1957. A mechanical model for human attention and immediate memory. Psychological Review 54, 205-215. Bursill, A.E., 1958. The restriction of peripheral vision during exposure to hot and humid conditions. Quarterly Journal of Experimental Psychology 10, 113-129. Colavita, F.B., 1974. Human sensory dominance. Perception & Psychophysics 16, 409-412. Colavita, F.B. and D. Weisburg, 1979. A further investigation of visual dominance. Perception & Psychophysics 25, 345-347. Comsweet, D.M., 1969. Use of cues in the visual periphery under conditions of arousal. Journal of Experimental Psychology 80, 14-18. Deutsch, J.A. and D. Deutsch, 1963. Attention: some theoretical considerations. Psychological Review 70, 80-90. Easterbrook, J.A., 1959. The effect of emotion on cue utilization and the organization of behavior. Psychological Review 66, 183-201. Egeth, H.E. and L.C. Sager, 1977. On the locus of visual dominance. Perception & Psychophysics 22, 77-86. Foree, D.D., and V.M. LoLordo, 1973. Attention in the pigeon: the differential effects of food-getting vs. shock avoidance procedures. Journal of Comparative and Physiological Psychology 85, 551-558. Gibson, J.J., 1933. Adaptation, after-effect, and contrast in the perception of curved lines. Journal of Experimental Psychology 16, 1-31. Held, R., 1970. ‘Two modes of processing spatially distributed visual stimulation’. In: F.O. Schmidt (ed.), The neurosciences: second study program. New York: Rockefeller University Press. Hockey, G.R.J., 1970a. Effect of loud noise on attentional selectivity. Quarterly Journal of Experimental Psychology 22, 28-36. Hockey, G.R.J., 1970b. Signal probability and spatial location as possible cues for increased selectivity in noise. Quarterly Journal of Experimental Psychology 22, 37-42. Hockey, G.R.J., 1970~. Changes in attention allocation in a multicomponent task under loss of sleep. British Journal of Psychology 61, 473-480. Hockey, G.R.J., 1979. ‘Stress and the cognitive components of skilled performance’. In: V. Hamilton and D.M. Warburton (eds.), Human stress and cognition: an information processing approach. New York: Wiley. Klein, R.M., 1977. Attention and visual dominance: a chronometric analysis, Journal of Experimental Psychology: Human Perception and Performance 3, 365-378. McIlwain, J.T., 1966. Some evidence concerning the physiological basis of the periphery effect in the cat’s retina. Experimental Brain Research 1, 265-271. Norman, D.A., 1968. Toward a theory of memory and attention. Psychological Review 75, 522-536. Pick, H.L., D.H. Warren and J.C. Hay, 1969. Sensory conflict in judgment of spatial direction. Perception & Psychophysics 6, 203-205. Pirenne, M.H., 1967. Vision and the eye, 2nd ed. London: Associated Book Publishers.

172

K. L. Shapiro, T.L. Johnson / Effects

of arousal

on

attention

Posner, MI., M.J. Nissen and R.M. Klein, 1976. Visual dominance: an information-processing account of its origins and significance. Psychological Review 83, 157-171. Randich, A.. R.M. Klein and V.M. LoLordo. 1978. Visual dominance in the pigeon. Journal of the Experimental Analysis of Behavior 30, 129-137. Rock I. and J. Victor, 1964. Vision and touch: an experimentally created conflict between the two senses. Science 143, 594-596. Sagi, D. and B. Julesz. 1985. ‘Where’ and ‘what’ in vision. Science 228, 1217-1219. Shapiro, K.L., B. Egerman and R.M. Klein, 1984. Effects of arousal on human visual dominance. Perception & Psychophysics 35, 547-552. Shapiro, K.L.. W.J. Jacobs and V.M. LoLordo. 1980. Stimulus-reinforcer interactions in the pigeon: implications for selective associations. Animal Learning & Behavior 8. 586-594. Wachtel, P.L., 1968. Anxiety, attention, and coping with threat. Journal of Abnormal Psychology 73. 137-143.