Effects of irregular preparatory intervals on reaction time in schizophrenia.

2 experiments attempted to (a) confirm previous observations that the slope of the negative relationship between reaction time (RT) and the length of the preparatory interval (PI) was steeper in schizophrenic than in normal Ss, and (b) investigate the effects of the PI on one trial on RT to the subsequent trial (PPI). The results show that the curves relating the PI with RT are significantly steeper for the patients even when differences in "baseline" RT level are controlled. Also, the detrimental effects of long PPIs are much greater for the schizophrenics. The data suggest that instead of establishing a generalized preparatory set, the schizophrenic Ss simplify the task by basing their pattern of preparation largely on the just preceding trial. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prior experimenter-subject relationships on reinforced reaction time of schizophrenics and normals.

The hypothesis was tested that deficits in schizophrenics' responses to positive social reinforcers would be reduced if reinforcers were delivered by an E who had first related to the Ss in a warm and accepting manner. Reaction times of 39 chronic schizophrenics and 39 normal adults were tested without and with reinforcement after exposure to 1 of 3 conditions of contact with E: (a) no contact, (b) contact with an unresponsive and aloof E, and (c) contact with a warm and accepting E. Schizophrenics had slowest reaction times after c. Normals had slowest reaction times after c until reinforced; on reinforced trials there were no differences between conditions for normal Ss. The results indicate that chronic schizophrenics can be motivated to gain approval but that such motivation in schizophrenics is more dependent upon immediate social circumstances than it is in normal adults. (29 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual perception of sequential numerosity by normals and retardates.

Presented sequences of 2-10 50-msec light flashes at interstimulus intervals (ISIs) of 100, 200, 300, 400, 500, and 600 msec. for multiple- and single-locus conditions to 20 educable retardates and 20 equal MA normals. Numerosity discrimination of the younger, normal children was more accurate at all ISIs (p     

A comparison of mental retardates and normals on kinesthetic figural aftereffects.

The reactivity of normals and retardates was compared on tests of visual and kinesthetic afteraffects. Mental retardates were shown to be characterized by a weaker satiation process than normals of comparable CA. From Psyc Abstracts 36:04:4JI86S. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of mental retardates and normals on the rotating trapezoidal window illusion.

56 high-grade institutionalized adolescent retardates and 56 normals of equated CA were, after training, split into 4 groups: Groups I and II observed a rotating trapezoidal window monocularly and binocularly, respectively; Groups III and IV observed a rotating trapezoidal shape, which had no windows cut out or shadows painted on it, monocularly and binocularly, respectively. Analysis of variance shows that visual conditions and stimuli are significant, but groups are not. The finding that retardates do not differ from normals on a reduced-cue ("experiential") illusion, contrasts with previous findings that they differ on full-cue ("physiological") illusions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size constancy in mental retardates and normals: A signal-detectability analysis.

Investigated size constancy differences among 11 institutionalized retardates, 6 noninstitutionalized retardates, 12 institutionalized normals (prison inmates), and 20 noninstitutionalized normals (college students) by psychometric function, signal detectability, and uncertainty analyses. Both retarded groups were perceptually deficient in making size judgments. This impairment paralleled that found between nonparanoid schizophrenics and normals by R. Price and C. Eriksen (see pa, vol. 40:9050). In addition, institutionalized retardates were less consistent in use of decisional rules than noninstitutionalized retardates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Slowness and the preceding preparatory interval effect in schizophrenia.

Measured the reaction times (RTs) of 25 schizophrenic (SCZ), 69 matched normal, and 14 bipolar Ss to a tone preceded by a preparatory interval (PI) of varying length. RTs increase when the PI for the immediately preceding trial (PPI) is longer than the PI for the current trial. Several studies have shown that this PPI effect is heightened in schizophrenia. The authors replicated this finding. However, they found that the size of the PPI effect within groups increased with overall slowness and that the least squares regression line relating the PPI effect difference score to overall slowness did not differ between groups, nor did SCZ Ss' regression line differ from that of normal Ss. Group differences on the PPI effect were also analyzed by taking residuals for members of all groups from the normal Ss' regression line of the PPI effect difference score on overall slowness. Groups did not differ on these residuals, nor did SCZ Ss differ from normal Ss. The authors conclude that the heightening of the PPI effect in schizophrenia is like that observed in equally slow normal Ss. This finding suggests that the PPI effect does not appear to be a promising marker of a distinctive SCZ pathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proprioception in schizophrenics and normals: Effects of stimulus intensity and interstimulus interval.

Obtained weight discrimination thresholds for 18 schizophrenics and 18 normals at various levels of weight intensity and presentation interval. The discrimination performances of all Ss were evaluated in terms of Weber ratio scores and the number of correct discriminations for each test condition. Differential effects attributable to diagnosis were found, with schizophrenics performing with less accuracy than normals at the lowest level of weight intensity. The different presentation intervals did not yield significant differences in discrimination. It is concluded that there is a proprioceptive deficit in schizophrenia which is due to inadequate sensory input and not to insufficient proprioceptive memory. Signal-detection theory is acknowledged as providing a possible alternative explanation of the results. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of mental retardates and normals on visual figural aftereffects and reversible figures.

"A group of institutionalized high-grade mentally retarded adolescent boys was compared with a group of normal boys, equated for chronological age, on two perceptual tasks." The results indicated that there was a significant difference between the groups in how they perceived visual figure aftereffects and rigidity with regard to the perception of a reversible figure-ground stimulus. The results are discussed in terms of theories of perception and similar findings with schizophrenics. 19 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual and saccadic reaction time with constant and variable preparatory intervals in schizophrenia.

Saccadic reaction time (RT) has been shown to be unimpaired in schizophrenia. Could this be due to its not requiring controlled information processing? The authors gave 49 schizophrenia patients and 34 controls manual and saccadic RT tasks with preparatory intervals of 1, 3, and 5 s given in regular and irregular sequences. If saccades require mainly automatic processes, they should not be affected by variations in the preparatory interval that are mediated by controlled processing. The manual task showed typical slower RT and larger preparatory interval effects in patients than in controls. Although the saccadic task showed significant effects of both the preparatory interval and the preparatory interval on the preceding trial similar in kind to those in manual RT, there were no group differences in these or in RT. The results are attributed to greater stimulus-response compatibility in the saccadic task, which puts fewer demands on working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical interstimulus interval in delusional schizophrenics and normals.

The critical interstimulus interval, the minimum interval between presentation of a test and mask stimulus at which the mask no longer interferes with processing of the test stimulus, was calculated for 10 schizophrenics with delusional symptoms and 10 normal college students. All Ss had previous experience with the masking procedure. Each S's critical interstimulus interval was obtained 4 times in 4 separate sessions. Results indicate a larger critical interstimulus inteval for the schizophrenics. All Ss also showed less masking with practice. Results are consistent with A. J. Yates's (see record 1966-05514-001) hypothesis of a schizophrenic deficit prior to cortical levels of information processing but were inconsistent with A. J. Yates and P. Korboot's (see record 1971-06730-001) findings that slow information processing is unique to chronic nonparanoid schizophrenics. Post hoc analysis suggests the possibility of an additional schizophrenic deficit in preattentive filtering. Directions for future research are discussed. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enumeration versus tracking during unimodal and multimodal sequential information processing in normals and retardates.

Presented varying length pulse sequences to 24 16-yr-old educable retardates, 24 equal chronological age (CA) normals, and 24 9-yr-old equal mental age (MA) normals under 3 modality switching conditions and 2 response modes. Error magnitudes were greatest for retardates, less for equal-MA normals, and least for equal-CA normals. Error magnitudes also increased significantly from the no switching to maximum modality switching condition, from the enumeration to motor tracking response mode, and with increasing numerosities. Error increases from enumeration to tracking and from no switching to maximum modality switching rates were predominantly underestimations, confirming previous findings that attention shifting interferes with input or storage of stimulus number. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of truncation on reaction time analysis.

Many reaction time (RT) researchers truncate their data sets, excluding as spurious all RTs falling outside a prespecified range. Such truncation can introduce bias because extreme but valid RTs may be excluded. This article examines biasing effects of truncation under various assumptions about the underlying distributions of valid and spurious RTs. For the mean, median, standard deviation and skewness of RT, truncation bias is larger than some often-studied experimental effects. Truncation can also seriously distort linear relations between RT and an independent variable, additive RT patterns in factorial designs, and hazard functions, but it has little effect on statistical power. A promising maximum likelihood procedure for estimating properties of an untruncated distribution from a truncated sample is reported, and a set of procedures to control for truncation biases when testing hypotheses is appended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biogenic amine-related enzymes and personality variations in normals

Altered activities of biogenic amine-related enzymes have been reported in some studies of patients with affective disorders and chronic schizophrenia. To evaluate whether any relationship between personality variations, including non-diagnosed psychopathology, and these enzymes might occur in non-psychiatric patients, 95 young adult volunteers were studied. Higher MMPI and Zuckerman sensation--seeking scale scores were found in male, but not female, volunteers with lower platelet and plasma amine oxidase activities. Males generally exhibited negative correlations, while females had positive correlations between the psychological test scores and amine oxidase activities. In contrast to the amine oxidase results, no associations were observed between plasma dopamine beta-hydroxylase activities and the personality variables.     

Effects of labels on the perception and discrimination learning of retardates.

Assessed the role of labels in perception in 54 familial retardates and 48 normal IQ children at 2 matched MA levels. 3 experimental manipulations were employed at each level in a factorial design. 1 group learned to associate a common label to random visual forms; a 2nd group learned distinctive labels to the same forms; finally, a 3rd group viewed the forms without labels. Following verbal training, all Ss received perceptual judgment and discrimination-learning tasks. No significant differences emerged between the retarded and normal Ss on paired-associate learning, discrimination learning, or perceptual accuracy without labels. In contrast to the normal children, however, the retardates' perceptual and learning processes were relatively unaffected by the learning of verbal levels. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Slowness and the preceding preparatory interval effect in schizophrenia": Correction.

Reports an error in the original article by M. B. Miller et al (Journal of Abnormal Psychology, 1993[Feb], Vol 102[1], 145–251). Three "hats' were left out of the equations on page 150. The corrected passage is presented. (The following abstract of this article originally appeared in record 1993-25729-001.) Measured the reaction times (RTs) of 25 schizophrenic (SCZ), 69 matched normal, and 14 bipolar Ss to a tone preceded by a preparatory interval (PI) of varying length. RTs increase when the PI for the immediately preceding trial (PPI) is longer than the PI for the current trial. Several studies have shown that this PPI effect is heightened in schizophrenia. The authors replicated this finding. However, they found that the size of the PPI effect within groups increased with overall slowness and that the least squares regression line relating the PPI effect difference score to overall slowness did not differ between groups, nor did SCZ Ss' regression line differ from that of normal Ss. Group differences on the PPI effect were also analyzed by taking residuals for members of all groups from the normal Ss' regression line of the PPI effect difference score on overall slowness.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of motivating instructions on reaction time in cerebral disease.

The purpose of the study was to determine the reaction time responsiveness of hospitalized, brain-injured patients to 3 types of motivating instructions and to compare their performances with those of a similar group of hospitalized medical patients without cerebral disease. Ss were 195 patients, 78 brain-injured, and 117 not. Marked initial differences in reaction time between the brain-damaged and control Ss were found, but these differences were not related to criterion scores within any of the 6 diagnosis-instructions combination. Within each diagnostic group the urging instructions were significantly superior to the other instructions in effecting improvements in performance. However, there was a suggestion that relaxing instructions might be more effective than standard instructions with brain-damaged Ss. 19 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of biological and social motivation on schizophrenic reaction time.

Reaction times of schizophrenic and normal Ss were determined under instructions to respond as fast as possible to a buzzer signal. Half of the Ss were retested immediately under the same conditions, while the other half were shocked on the responding finger simultaneously with the buzzer. Schizophrenics' RTs improved significantly under shock conditions. Disturbances in schizophrenic RT are "partially accounted for by defective social motivation and… a biological deficit may be involved in the reactions of more chronic schizophrenics." 21 references. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Schizophrenia: Effects of inheritance and rearing on reaction time.

Studied both manual and verbal reaction time in 4 selected groups of adult Ss (N = 258) in an attempt to uncover hereditary and environmental influences on the reaction time of Ss whose parents do or do not have schizophrenic disorders. The groups included (a) adoptive offspring of schizophrenic parents (adoptive index); (b) adoptive offspring of nonschizophrenic parents, but whose adoptive parents had a psychiatric record of schizophrenic disorder (cross-foster); (c) adoptive offspring of nonschizophrenic parents (adoptive control); and (d) offspring of schizophrenic parents who were reared by their biological parents (nonadoptees). Analysis of variance was used to assess the effects of rearing by a schizophrenic parent, a genetic background for schizophrenia, and interaction between rearing and genetic background. Groups opposed for genetic background for schizophrenia were not different in reaction time performance, while groups opposed for rearing by a schizophrenic parent were significantly so. Mean reaction time was slower in groups reared by a schizophrenic parent than in those reared by a nonschizophrenic parent. There was no significant interaction between rearing and genetic background for reaction time performance. (French summary) (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning time of schizophrenics and normals for visual designs.

Measured the time to locate a target design in an array of 4 designs by 12 process and 12 reactive schizophrenics and 12 hospitalized and 12 nonhospitalized normal controls. Designs and arrays differed in the size of the rotation and reflection equivalence sets from which they were selected. Differences in mean reaction time (RT) attributable to these characteristics were found as expected. Schizophrenics performed slower than the nonhospitalized normals. The mean RT of hospitalized normals, mostly spinal cord injury patients, fell between that of the process and reactive schizophrenics. No Group * Stimulus Condition interaction effects were found. Results are interpreted as not supporting leading theories of schizophrenic deficit. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)