Effects of extraneous stimuli on social cue perception in schizophrenia

ELSEVIER Psychiatry Research 56 ( 1995) Ill- 120

PSYCHIATRY

RESEARCH

Effects of extraneous stimuli on social cue perception in schizophrenia

Patrick W. Corrigan*, Ilana B. Addis

University of Chicago, Center for Psychiatric Rehabilitation, 7230 Arbor Dr., Tinley Park, IL 60477, USA

Received 10 February 1994; revision received 22 July 1994; accepted 25 October 1994

Competing hypotheses that explain the effects of emotionally arousing, extraneous auditory stimuli on the social cue perception of schizophrenic patients were examined in this study: (1) extraneous arousing stimuli enhance patients’ cue perception; (2) extraneous stimuli distract patients, and cue perception is diminished. Twenty-five patients with DSM-III-R diagnoses of schizophrenia completed a cue-perception task in which half of the videotaped vignettes included in the task were presented with simultaneous extraneous stimuli and half were not. Item difficulty and consistency across extraneous stimuli conditions were matched on standardization and cross-validation samples. Results showed that schizophrenic subjects were significantly more sensitive to cues when exposed to extraneous stimuli, thereby supporting the first hypothesis. This effect was also observed in a subgroup of schizophrenic subjects who demonstrated a distraction decrement on another test of short-term recall. The presence of extraneous stimuli in- teracted with perception of abstract cues; that is, schizophrenic subjects were particularly better at perceiving abstract cues when extraneous stimuli were presented simultaneously. Future research needs to determine characteristics of extraneous stimuli that enhance cue perception.

Keywords: Attention; Intelligence; Information processing

1. lntrodwtion

Several studies have examined schizophrenic patients’ sensitivity to interpersonal stimuli to better understand the social dysfunctions that covary with the deficit syndrome and to design social rehabilitation programs. Specifically, research has shown that schizophrenic subjects are less sensitive

* Corresponding author, Tel: +I 708 614 4770; Fax: +I 708 614 4780.

than comparison groups to facial affect (Morrison et al., 1988), nonverbal body cues (Rosenthal et al., 1979; Monti and Fingeret, 1987), and situational stimuli (Corrigan et al., 1990; Mueser et al., 1993). Perception of the stimuli that describe interpersonal situations has been of particular interest to clinical investigators because of their relevance for understanding social skills (Forgas, 1983). Research into situational stimuli has examined the recognition by patients of the concrete cues (e.g., specific percepts corresponding with

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112 P. W. Corrigan. I. B. Addis / Psychiatry Research 56 (1995) 1 I1 -120

what actors said and did) and abstract cues (in- ferences from these basic percepts about the rules and goals guiding the actors’ behavior) that define an interpersonal situation. Results showed schizophrenic subjects to be significantly less able to recognize the abstract cues, rather than the concrete cues, of videotaped social situations (Corrigan and Green, 1993).

Abstract and concrete cue recognition has been shown to interact with the psychophysiological arousal engendered by the interpersonal situation. Earlier research demonstrated that psychophysiological arousal in schizophrenic subjects can be manipulated by showing patients vignettes that vary in emotional intensity (Corrigan et al., 1989); cardiovascular indices increased significantly after viewing of vignettes that schizophrenic subjects rated as more emotionally arousing. A subsequent study showed that abstract cue recognition improved significantly when schizophrenic patients viewed moderately arousing situations (e.g., a hus- band and wife arguing) compared with low arousing vignettes (e.g., three friends playing cards) (Corrigan and Green, 1993). No such changes were observed in concrete cue recognition.

These findings suggest that arousing situational stimuli might be enlisted to improve the perception of abstract cues. Perhaps, patients viewing a test situation will better recognize cues in that situation when concomitant, emotionally arousing stimuli are presented. For example, patients may better identify cues that correspond to a vignette in which two friends are assembling a puzzle if presentation of the vignette is accompanied by inspirational music. This hypothesis, however, seems to contradict well-documented findings about the effects of distraction on short-term recall memory in schizophrenic patients. In prototypical studies of this type, patients are asked to recall short lists of numbers read to them by a female voice while ignoring a distractor list simultaneously read by a male voice (Oltmanns and Neale, 1975; Oltmanns, 1978; Oltmanns et al., 1978; Finkelstein, 1983; Rund, 1983; Corrigan and Green, 1991). Findings have, for the most part, shown that schizophrenic patients recalled significantly fewer numbers when items were read in the presence of a distractor. Oltmanns and Neale (1975) concluded that

schizophrenic patients are especially sensitive to the deleterious effects of distraction.

These disparate research programs lead to competing hypotheses about the effects of external auditory stimuli on the social cue perception of schizophrenic patients. We hypothesize that schizophrenic subjects will better recognize social cues when concomitant emotionally arousing stimuli are presented if a stimulus enhancement effect is valid. Alternatively, schizophrenic subjects will be significantly less sensitive to social cues with concomitant stimuli if a distraction effect is operative.

2. Methods

2.1. Standardization of stimulation task To assess sensitivity to interpersonal cues, sub-

jects in a standardization sample were administered the Social Cue Recognition Test @CRT) in which they were instructed to watch eight videotaped vignettes and then answer true-false questions about the concrete and abstract cues viewed in the interaction (Corrigan et al., 1990; Corrigan and Green, 1993). Extraneous auditory stimuli were presented during half of the vignettes, a segment from a professionally prepared audiotape of a Star Trek episode. The Star Trek episode included theme music and a brief, dramatically read narrative of the episode. It was reliably selected (KR-20 = 0.77) during a pilot study (n = 13) as the most “arousing” and least “dreary” of a set of five audiotaped segments (P.W. Corrigan and I.B. Addis, unpublished raw data, 1993). No other extraneous stimuli were presented with the remaining four vignettes. Vignettes alternated in the presence or absence of extraneous stimuli.

SCRT vignettes were presented on a 204nch color television placed at eye level 6 feet in front of the subject. Star Trek sounds were produced from a speaker placed at ear level 3 feet to the subject’s left. Dialogue and background sounds in the SCRT vignettes varied between 60 and 70 dB, while stimuli in the Star Trek episode varied between 55 and 63 dB.

Forty-eight true-false items were written to assess cue recognition for each of the eight vi-

P. W. Corrigan, I. B. Addis /Psychiatry Research 56 (1995) I I I - I20 113

gnettes. Of these 48 items, 22 represented targets Or cues that actually occurred in the vignette (and so were correctly answered “True”) and 26 represented nontargets (correctly answered “False”). Of the 22 targets, 1 I represented concrete cues (cues that could be seen or heard directly; e.g., “Harry is wearing a bright red undershirt”) and 11 represented abstract cues (about the underlying affect and goals; e.g., “Doris’s goal in this situation is to get to sit in Harry’s chair”). Similarly, of the nontargets, 13 represented concrete cues and 13 represented abstract cues. Three independent judges rated each item on whether it was representative of the concrete or abstract domain and on whether it could be accurately answered given the information provided in the tape. Only 17 of the 384 items needed to be modified after this evaluation.

Several precautions must be taken to assess differential responding across stimulus/no-stimulus conditions. Chapman and Chapman (1973, 1978) warned that the magnitude of psychiatric patients’ performance decrements between any two tasks may be a function of differences in the discriminating power of the component tests. In cases in which the difference in discriminating power between tests is large, differential deficit attributed to patient groups may arise from psychometric con- found rather than a true difference. Differences in discriminating power across SCRT conditions can be lessened by matching items in the component tests for difficulty and reliability on a standardization group of normal control subjects (Chapman and Chapman, 1973, 1978). To match for item difficulty, the eight vignettes and 384 SCRT true- false items were administered to 67 subjects in five small groups of about 10 to 15 subjects; data from 11 of the 67 subjects were omitted because of un- corrected vision (n = 4), hearing problems (n = 3), or previous history of psychiatric hospitalization (n = 4).

The remaining sample was 45.4% male and had an average age of 35.5 years (SD = 7.7). Subjects had completed 15.1 years of education on average (SD = 1.5) and were 61.1% white, 29.6% African American, 7.4% Hispanic, and 1.9% Asian. The standardization sample had a mean IQ on the Shipley Hartford of 103.1 (SD = 9.2).

To diminish differences in the discriminating power of the four tasks, item difficulties were determined for target and nontarget items; items were then omitted so that mean item-difficulty levels representing targets and nontargets across conditions were optimal (Lord, 1952). As can be seen in Table 1, the means and standard deviations of item difficulties for targets and nontargets were similar (F = 0.10 and 0.52, respectively; df = 3, 162; P’s > 0.50). Item consistencies (KR-20) were a little more variable, however, but they exceeded suitable values reported in similar studies (Kerr and Neale, 1993).

Standard indices of performance on cue- perception tasks like the SCRT include correct- identification rate (percentage of true items reported as true) and false-positive rate (percentage of false items reported as true). However, these indices are biased by the perceived payoffs for correct identifications and incorrect attribu- tions (Davies and Parasuraman, 1982); for example, one subject who believes that there is no harm in mistaken cue perception may say all items are true, while another subject who believes false- positive responses are a grave error is likely to answer true infrequently. To obviate this problem, a cue-sensitivity index (A ‘) derived from signal- detection theory is reported here. A’ is free of payoff biases and is derived from correct- identification rates (Cl) and false-positive rates (FP), as shown in the equation below:

A’=$+ (Cl- FP) (1 + CI- FP)

4CZ(l - FP)

Signal-detection principles are not typically applied to tasks that load heavily on memory func- tions. Several assumptions about the distribution of signal and noise may be violated in short-term recall tasks like the SCRT (Davies and Parasur- aman, 1982). However, although signal-detection parameters representing short-term recall need to be evaluated cautiously, this perspective has been used in other research to improve interpretation of performance on recognition-memory tasks (Banks, 1970; Lockhart and Murdock, 1970; Cor- rigan and Green, 1991, 1993). Moreover, the num-

114 P. W. Corrigan, LB. A&is/ Psychiatry Rrseorch 56 (1995) III-120

Table 1 Difficulty and consistency (AR-20) of target and nontarget items on the four conditions for the standardization and cross-validation samples

Item difficulties

Target items Nontarget items A’

Task Mean SD KR-20 Mean SD KR-20 Mean SD

Stanabrdizotion sample Concrete cues

Extraneous stimulation 82.1% 9.4% 0.66 6.5% 2.3% 0.69 0.93 0.03 Neutral condition 82.6 16.9 0.81 5.3 1.9 0.72 0.94 0.03

Abstract cues Extraneous stimulation 82.6 16.6 0.77 6.3 2.6 0.78 0.93 0.03 Neutral condition 82.6 17.4 0.93 6.4 2.5 0.82 0.93 0.03

Cross-validation sample Concrete cues

Extraneous stimulation 86.2% 10.3% 0.69 6.3% 8.2% 0.73 0.94 0.07 Neutral condition 84.9 7.5 0.78 5.6 15.2 0.76 0.94 0.04

Abstract cues Extraneous stimulation 86.4 4.1 0.14 8.8 17.9 0.73 0.94 0.04 Neutral condition 86.3 7.8 0.85 11.7 21.5 0.78 0.93 0.06

Note. A’, a cue-sensitivity index derived from signal-detection theory (see text).

ber of targets and nontargets included in a standard signal-detection paradigm far exceeds the number of items in the SCRT. Still, the number of SCRT items is sufficient to describe a signal-noise distribution and derive appropriate signal- detection parameters (Davies and Parasuraman, 1982).

A ’ for the standardization group was determined for each condition from the mean item diffkulties of targets (also equal to the mean correct-identification rate for the sample) and the mean item difficulties of nontargets (equal to the mean false-positive rate); A ’ for each condition is included in the right-hand column of Table 1. Note that the means and standard deviations of A ’

were similar across conditions (F = 0.11; df = 3, 162; P > 0.50).

Findings on the standardization sample were cross-validated on a second sample of 15 subjects drawn from the nursing staff at a local state hospital. Subjects in this group were screened with a lifetime version of the expanded Present State Examination (Wing et al., 1974); clinicians con- ducting the interviews were trained to a minimum

agreement of 85% for the presence of symptoms according to criterion ratings of our laboratory. Cross-validation subjects who reported a history of psychotic disorder, personality disorder, organicity, or substance dependence were ruled out. Moreover, potential subjects in this sample who had first-degree family members with severe mental illness were excluded. The average age of subjects in the cross-validation sample was 41.7 years (SD = 7.5), and they had completed 14.5 years of education on average (SD = 3.2). The cross-validation sample was 80% female, 73.3% African American, and 26.7% white. Marital status was as follows: 20.0% were single, and 80.0% were married or divorced. The revised version of the SCRT was individually administered to members of the cross-validation group.

Table 1 presents the means and standard deviations of item diffkulties for targets and nontargets in the standardization and cross-validation samples. Note that although target-item difficulties were similar across conditions within the cross- validation sample (F = 0.14; df = 3,42; P > 0.50), item difficulties of targets were significantly higher

P. W. Corrigan. I.B. Addis / Psychiatry Research 56 (1995) III-120 115

for cross-validation compared with standardization subjects (F = 4.32; df = 1, 60; P < 0.05); this may have occurred because cross-validation subjects were administered the SCRT individually, whereas standardization subjects were administered the test in small groups. Moreover, item difficulties for nontargets were not similar across the four conditions within the cross-validation sample (F = 5.37; df = 3,42;, P > 0.01). However, A ‘, the variable of central interest in this study, was similar across conditions within the cross- validation sample (F = 0.81; df= 3, 42; P > 0.50) and similar to A ’ across the four conditions of the standardization sample (F = 0.33; df = 1, 58; P > 0.50). Item consistencies across conditions for the cross-validation sample were suitable. We concluded, therefore, that differences in discriminating power of A ’ across the four SCRT conditions had been minimized; patient differences across these conditions were not likely to represent psychometric confounds.

2.2. Extraneous stimuli and cue perception in schizophrenic patients

Subjects with DSMZZZ-R diagnoses (American Psychiatric Association, 1987) of schizophrenia were recruited for the study. All diagnoses were based on an expanded version of the Present State Examination conducted by the same reliable raters who made assessments in the cross-validation sample.

Schizophrenic subjects with histories of drug or alcohol abuse during the past year or who met DSM-III-R criteria for withdrawal or dependence during their lifetimes were excluded. Moreover, subjects with chart histories of organic mental disorder, head trauma, or mental retardation were excluded. The schizophrenic subjects also demonstrated at least a fourth grade reading level as measured by the Wide Range Achievement Test- Revised (Jastak and Wilkinson, 1984) and had corrected vision of at least 20130 as measured on the Snellen eye chart. Subjects were administered the Acoustic Recognition Test (ART; Merrick, 1992) to exclude individuals with primary auditory deficits. The ART is a 30-item task in which subjects are instructed to point to the one of four pic- tures that best represents a common household

sound played over an audiotape. Subjects scoring below the 85th percentile on the ART were excluded.

Twenty-five schizophrenic subjects completed the protocol; they had a mean age of 34.1 years (SD = 8.7) and mean years of education of 12.4 (SD = 2.3). The schizophrenic sample was 52.0% female; they were also 64.0% African American and 36.0% white. A’ from the SCRT for the four conditions was not found to differ significantly across gender or ethnic groups. Marital status was as follows: 76.0% were single, and 24.0% were married or divorced. Marital status is thought to be an approximate measure of social role adjustment (Weissman, 1975). In support of this assump- tion, SCRT variables indicating cue perception were significantly larger (P < 0.01) for the married/divorced schizophrenic subjects.

The distribution of number of days hospitalized in the past 6 months was bimodal; 29.6% of the sample was drawn from the extended care units of a state hospital and had been hospitalized for all of the preceding 6 months. The remaining 70.4% of the sample was drawn from a partial hospitalization program and had been hospitalized for fewer than 30 days of the preceding 6 months. A ’ values for the four SCRT conditions did not correlate significantly with days of hospitalization. Subjects were administered the expanded 24item version of the Brief Psychiatric Rating Scale (BPRS; Lukoff et al., 1986) to measure current level of psychiatric symptoms. Raters who conducted BPRS interviews had been trained previously to a minimum intraclass correlation (ICC [l,l]; Shrout and Fleiss, 1979) of 0.80 based on consensus ratings at our laboratory. Two sum- mary scores, identified in a factor analysis by Overall et al. (1967), were determined: a Thinking Disturbance factor (equal to the average of con- ceptual disorganization, hallucinations, and un- usual thought content) and a Withdrawal/ Retardation factor (equal to the average of blunted affect, emotional withdrawal, and motor retardation). Factor scores for Thinking Distur- bance (mean = 2.9, SD = 1.2) and Withdrawal/ Retardation (mean = 1.9, SD = 0.2) showed the samples to be mildly symptomatic. A ’ values for the four SCRT conditions were not found to be

116 P. W. Corrigan, I.B. Addis/Psychiatry Research 56 (1995) 111-120

significantly correlated with Thinking Disturbance or Withdrawal/Retardation.

2.4. Procedure

All patients received neuroleptic medications with the average dose equal to 540 chlorpromazine equivalents (SD = 441). All patients also received benztropine for side effects with the average dose equal to 1.0 mg (SD = 1.3). There were no significant correlations between medication levels and A ’ scores on the SCRT.

Subjects were recruited and informed about the purposes of the study. Total testing time for those who agreed to participate required 2 to 3 hours, depending on mental status, and was completed over three sessions within a l-week period. Schizophrenic subjects received candy and soft drinks, regardless of performance, for completing the measures.

2.3. Other measures 3. Results The effects of extraneous stimuli as distracters

have been measured using the Digit Span Distrac- tion Test (DSDT). The DSDT was administered in this study as an independent assessment of the effect of distraction on patients. Two versions of the DSDT were used: a short series comprising seven nondistractor lists of six digits interspersed with seven distractor lists of live digits followed by a long series comprising seven nondistractor lists of seven to eight digits interspersed with seven distractor lists of six digits (Oltmanns and Neale, 1975). An audiotaped female voice read the target numbers, and a male voice read the distractor numbers. After each list, the tape recorder was shut off and subjects were instructed to write down, in order, as many numbers as they could remember. In the procedure followed by Rund (1983), number of individual digits recalled in the correct order was totaled and divided by the number of possible correct answers per condition: short list with distraction, short list without distraction, long list with distraction, and long list without distraction.

Table 2 presents mean sensitivity findings for the extraneous stimuli x abstraction conditions for schizophrenic patients. To determine the effects of cue abstraction and extraneous stimuli on cue sensitivity (A ‘) for the schizophrenic subjects, a 2 x 2 analysis of variance (ANOVA: extraneous stimuli x cue abstraction) was conducted. No significant differences were found in cue sensitivity (A ‘) across abstraction conditions (F = 0.49, df= 1, 24; NS). However, a significant difference was found for presence of extraneous stimuli (F = 4.65; df = 1, 24; P < 0.05), with patients being more sensitive to cues after viewing a vignette with simultaneous extraneous stimuli. Moreover, a significant interaction suggested that differences in abstract and concrete cue identification varied in the presence of extraneous stimuli (F = 4.77; df = 1, 24; P < 0.05).

To determine under which conditions social cue sensitivity was significantly enhanced, matched pairs r-tests comparing the four sensitivity scores of the patient sample were carried out. Results

Verbal intelligence was measured to determine whether intelligence accounted for the effects of extraneous stimuli on cue perception. IQ was estimated from subjects’ scores on the Vocabulary Subtest of the Wechsler Adult Intelligence Scale- Revised (WAIS-R). The Vocabulary Subtest was selected because it has been shown to correlate highly with overall and verbal intelligence (from 0.74 to 0.84) (Zimmerman and Woo-Sam, 1973; Wechsler, 19gl). The patient sample had an average WAIS-R Vocabulary score of 30.5 (SD = 15.4); this value represents a scale score of 7, which is one standard deviation below the mean of the WAIS-R standardization sample (Wechsler, 1981).

Table 2 A’ for the four test conditions for schizophrenic subjects

Test condition

Concrete cues, extraneous stimulation

Concrete cues, neutral condition Abstract cues, extraneous

stimulation Abstract cues, neutral condition

A’ for schizophrenic subjects

Mean SD

0.88 0.05

0.88 0.05 0.89 0.04

0.85 0.06

P. W. Corrigan. I. 8. Addis/ Psychiatry Research 56 (1995) III-120 117

showed that abstract cue sensitivity was significantly greater when extraneous stimuli were present (t = 2.79, df = 24, P < 0.01). Moreover, nonsignificant trends suggested that concrete cue perception with extraneous stimuli was better than abstract cue perception without extraneous stimuli (t = 1.72, df = 24, P < 0.10).

3.1. Digit Span Distraction Test Table 3 presents mean scores on four conditions

of the DSDT for the schizophrenic sample; only 2 1 subjects completed this measure. Although a significant difference was found in length of digit span (F = 33.62; df= 1,20; P < O.OOOl), no significant differences were demonstrated between distraction and nondistraction conditions (F = 0.03; df = 1, 20; NS) nor was the interaction significant (F = 0.10; df = 1,20; NS). The fact that these findings diverge from earlier reports (cf. Oltmanns and Neale, 1975) suggests that the present sample of patients may differ from those studied by other investigators who have demonstrated the deleterious effects of distraction. The possibility must be considered that the effects of extraneous stimuli and social cue perception found could have been attributable to an unrepresentative sample.

To determine whether SCRT findings were unique to the sample included in this study, patients were divided by DSDT scores according to those who showed a decrement due to distraction and those who did not; one subject showed no dif-

Table 3 Correct identification rates for the Digit Span Distraction Test (DSDT) for the full sample and for the subsample of schizophrenic subjects showing the recall decrement due to

distraction

DSDT condition

Short list With distraction Without distraction

Long list With distraction Without distraction

Full sample (N = 25)

Mean SD

0.62 0.28 0.63 0.25

0.49 0.23 0.49 0.25

Subsample (II = IO)

Mean SD

0.59 0.26 0.67 0.20

0.46 0.20 0.57 0.21

ference across DSDT conditions and therefore was not included in these analyses. The right-hand column of Table 3 summarizes DSDT scores for the 10 patients in the distraction-decrement group. Similar to findings in the study of Oltmanns and Neale (1975), the subgroup showed significant effects for distraction (F = 21.44; df = 1, 9; P = 0.001) and length of list (F = 11.53; df = 1, 9; P = O.OOS), but not the interaction (F = 0.42; df = 1, 9; NS). Interestingly, the distraction decrement group also resembled Oltmanns and Neale’s sample in course of illness; patients showing the distraction decrement had significantly more days of hospitalization during the preceding 6 months compared with the other patients (F= 10.79; df = 1, 18; P = 0.004). The distraction-decrement group did not differ significantly from the remaining patients on demographic variables, medication levels, or psychiatric symptoms as measured on the BPRS.

Table 4 summarizes cue sensitivity across the four conditions for the distraction decrement subsample, which showed trends similar to those in the whole sample. Results of a 2 X 2 ANOVA for this group showed that subjects performed better when viewing situations with extraneous stimuli (F = 7.42; df = 1, 9; P = 0.02). Effects for cue abstraction (F = 0.34; df = 1, 9; NS) and the interaction were nonsignificant (F = 0.54; df = 1, 9; NS).

3.2. Verbal intelligence and the effects of extraneous stimuli

The four conditions of the SCRT in this study were matched for item diffkulty and item con-

Table 4 A ’ scores for the four test conditions for the subsample of schizophrenic subjects with a distraction decrement on the Digit Span Distraction Test

Test condition

Concrete cues Extraneous stimulation Neutral condition

Abstract cues Extraneous stimulation Neutral condition

A’

Mean

0.89 0.88

0.90 0.86

SD

0.04 0.06

0.03 0.06

118 P. W. Corrigan. I. B. Addis / Psychiatry Research 56 (1995) Ill-120

sistency on standardization and cross-validation samples to diminish differences in discriminating power across conditions. As a result, differences in effects of extraneous versus neutral stimuli for the schizophrenic subjects are likely not to be attributed to generalized performance deficits. How- ever, the cross-validation and schizophrenic samples differed significantly in levels of verbal intelligence as estimated by the Vocabulary Subtest of the WAIS-R (F= 8.44; df = 1, 37; P < 0.01); one subject in the cross-validation sample did not complete the Vocabulary Subtest. We have argued elsewhere that verbal intelligence is an approximate measure of generalized deficit (Corrigan, 1994). Therefore, we need to determine whether verbal intelligence accounts for the differential deficit in cue recognition due to extraneous stimuli.

Chapman and Chapman (1989) warned that significant correlations between difference scores (e.g., extraneous stimuli cue perception minus neutral stimuli cue perception) and measures of cognitive functioning like intelligence may be spurious because they may instead represent correlations between intelligence and overall sensitivity (i.e., extraneous stimuli cue perception plus neutral stimuli cue perception). These spurious findings can be diminished by using standardized residual scores (z,,d of the form:

ext - eitt zext =

where ext is the observed SCRT sensitivity (A ‘) in the presence of external stimuli, edit is the predicted value based on a regression equation determined from the standardization group (with A ’ during the neutral stimuli as the independent variable),

and SL.ncut is the standard error. No significant Pearson product-moment cor-

relations were found between zeXt and the WAIS- R Vocabulary Subtest for subjects in the schizophrenic sample (r = -0.12) or, for that mat- ter, in the cross-validation group (r = -0.27). However, nonsignificant trends suggested a possible association between overall sensitivity across SCRT conditions and the Vocabulary Subtest score for the schizophrenic patients (r = 0.34, P < 0.10). No sigh&ant association was found be-

tween overall SCRT A ’ and the WAIS-R Vocabu- lary Subtest score for cross-validation subjects (r = -0.13).

4. Discumion

The purpose of this study was to determine the effects of extraneous auditory stimuli on the perception of cues that describe social situations. Re- sults suggested that schizophrenic subjects who observed short vignettes with extraneous stimuli were significantly more sensitive to the social cues within the situation -what we will call a stimulus- enhancement effect. Given that the extraneous stimuli and neutral tasks were matched for item difficulty on standardization and cross-validation groups, this difference is not likely to be attributable to generalized deficits in the patient sample. The fact that differences in cue perception across extraneous and neutral stimuli were also not found to be significantly associated with verbal intelligence provides additional evidence in support of the differential deficit.

A stimulus-enhancement effect is strikingly dif- ferent from the distraction effect found in previous cognitive research on schizophrenia (e.g., Oltmanns and Neale, 1975). We have attributed the stimulus-enhancement effect, at least in this study, to qualities of the extraneous stimuli and not of the social cues. The presentation of emotionally arousing stimuli increases the autonomic arousal of the viewer; Yerkes and Dodson have described the relationship between task performance and psychophysiological arousal as an in- verted U. The emotionally arousing stimuli improve cognitive performance by elevating arousal to optimal moderate levels. Many schizophrenic patients are assumed to be tonically hypoaroused due to antipsychotic medications or negative symptoms (Spohn et al., 1977; Dawson and Nuechterlein, 1984); mildly arousing extraneous stimuli increase the patient’s psychophysiological arousal, and performance is improved. However, hyperaroused patients could con- ceivably demonstrate a recognition decrement after extraneous emotional stimuli. When levels of psychophysiological arousal at the apex of the in- verted U are exceeded significantly, performance

P. W. Corrigan. I. B. Addis /Psychiatry Research 56 ( 1995) I I I-120 119

may diminish. Future research needs to map out the relationship between patients’ baseline arousal and the effects of extraneous stimuli.

The effect of stimulus enhancement seems to interact with the abstraction dimension of cue recognition. Patients in this study were significantly more sensitive to abstract cues when extraneous stimuli were presented during the vignette. This finding is consistent with previous findings that abstract cue recognition increases in situations that are more psychophysiologically arousing (Corrigan and Green, 1993). It is interesting that the effects of extraneous stimuli seem to be specific to abstract cue sensitivity with little influence on the perception of concrete cues. This finding may represent a ceiling effect; given the generalized cognitive deficit of schizophrenic patients, cue sensitivity never exceeds a below normal A ’ of ap- proximately 0.90 (Corrigan and Green, 1993). Concrete cue perception generally occurs at the ceiling. Additional arousal due to extraneous stimuli raises abstract cue perception to the same ceiling.

The DSDT was added to the research protocol as a parallel measure of the distracting effects of extraneous stimuli. However, the complete sample of schizophrenic subjects in this study showed no deficit in digit span recall across conditions, a tind- ing that differs from other reports (Oltmanns and Neale, 1975; Oltmanns, 1978; Oltmanns et al., 1978; Finkelstein, 1983; Rund, 1983; Corrigan and Green, 1991). Subjects in the earlier studies were, for the most part, symptomatic inpatients, while our sample was a mix of inpatients and relatively remitted outpatients. The DSDT distraction effect was seen for a subsample of patients in our study who were primarily inpatients and who had a significantly longer history of recent hospitalization. Analysis of cue-sensitivity data for the distraction-decrement sample showed the same pattern of stimulus enhancement. We conclude, therefore, that findings from this study do not seem to reflect responses of a unique sample of patients unlike those in whom the distraction decrement had been demonstrated.

Stimulus-enhancement effects are likely to vary with characteristics of the stimuli. A Star Trek episode was specifically chosen because of its

familiarity and emotionally stirring quality. Fu- ture research needs to examine which stimulus characteristics are particularly germane to the enhancement effect. Perhaps extraneous stimuli that are less arousing (e.g., a droning voice reading the tax code) will not show the stimulus- enhancement effect and may even yield a distraction decrement. Alternatively, the effects of stimulus enhancement may vary with time on task. The perception task in this study was relatively short. Perhaps the patient wearies more quickly during a longer vigilance task such that cue perception dwindles with stimulus enhancement.

Findings reported in this article have implica- tions for the practical management of patients. In particular, stimulus-enhancement strategies might be enlisted to improve the schizophrenic patients’ participation in social skills training classes. Pa- tients are more likely to attend to, and later recognize, information from these training sessions when classes are moderately arousing. This level of arousal may be fostered by use of inspirational music, interesting videotapes, or high-energy teaching styles. However, there are likely upper limits to the enhancing effects of arousing stimuli. Clinicians should be vigilant not to overarouse patients.

Acknowledgements

This project was made possible by a grant from the Louis Block Foundation. The authors thank Marjorie Jakus and Donna Weinberg for their assistance in data collection and Stanley McCracken and Paul Holmes for their cogent reviews of earlier drafts of the manuscript.

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Effects of extraneous stimuli on social cue perception in schizophrenia