Impairment in early stages of visual information processing in nonpsychotic schizotypic individuals.

Investigated the perceptual functioning of individuals whose MMPI-168 profiles indicated schizophrenic tendencies but who did not exhibit marked thought disorder. The MMPI 2-7-8 code type was used to identify these 15 Ss from a pool of 909 college students. This group was compared on a backward visual masking task with 2 control groups: (a) 14 Ss whose profiles were inflation free and (b) 11 Ss whose profiles showed elevations on any 2 scales except the Sc. Critical interstimulus interval (ISI) was used as the dependent measure. The 2-7-8 group required significantly longer critical ISI to recognize target letters than did the inflation-free group. Regression analysis showed that for the group that showed inflations on any 2 scales except Sc, Sc was a significant predictor of critical ISI. It is concluded that a deficit exists at a very early stage in the visual information processing system of the 2-7-8 group. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Order of processing in visual perception.

Three experiments tested predictions derived from 3 cognitive scanning hypotheses proposing respectively a left-to-right, ends-first, and peripheral-foveal order of scanning. In Exps I and II configurations of letters and/or digits were presented to 11 Ss around a central fixation point, and the stimulus was followed by a 1-sec presentation of a patterned mask or a blank white field. Backward masking selectively impaired the identification of stimuli in foveal positions whether or not these stimuli occupied middle-of-row positions. In Exp III 4 Ss made a manual same-different response to the presence or absence of a critical letter presented 3Deg. to the left or right of fixation. Noise letters appeared on either side or both sides of the critical letter. Identification response times were faster when the critical letter appeared in the left-most position in left field arrays and the right-most position in right field arrays. Principal conclusions drawn from the 3 experiments were: (a) Alphanumeric stimuli are scanned from the peripheral visual field inward towards fixation. (b) Any left-to-right scanning occurs relatively late in iconic processing. (c) An ends-first scanning strategy is a particular case of a more general peripheral-foveal strategy. (French summary) (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Categorization of disoriented faces in the cerebral hemispheres of normal and commissurotomized subjects.

We examined the capacity of the cerebral hemispheres to process faces that deviate from canonical perspective. In Experiment 1, normal Ss performed a gender categorization of faces presented at varying angular orientations in the left visual field (LVF) or right visual field (RVF). Orientation affected processing speed, more so in the RVF than in the LVF. The function relating reaction times to disorientation of the faces was approximately monotonic and reflected the increased difficulty in extracting relevant configurational information as the faces were rotated from canonical perspective. In Experiment 2, 3 commissurotomized Ss performed the same task. They responded above chance in the 2 visual fields, and the pattern of their results was similar to that obtained with the normal Ss, but the effect of disorientation was considerably more pronounced. It is suggested that the right hemisphere contribution becomes more critical the further the visual pattern departs from conventional view. Issues regarding the specification of processes correcting for disorientation and comparison of normal and commissurotomized Ss are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laterality and visual masking: Interhemispheric communication and the locus of perceptual asymmetries for words.

Exps I and II (with 16 17–32 yr old right handers) measured the critical interstimulus interval at which a word presented to the right or left field escaped a trailing noise or pattern mask. Perceptual asymmetries were absent in the noise mask condition. A right-field advantage of about 4 msec that did not vary with predictability of target location was found in the pattern mask condition. Exp III (8 Ss) showed that pattern masking leads to a right-field advantage even when accuracy is well below asymptote. Results suggest that hemispheric differences for word identification are either absent or inconsistent at early, peripheral stages of processing, but emerge strongly at higher-order central processing stages. The estimate of interhemispheric transmission times from these masking studies are on the order of 4 msec. (French abstract) (79 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Susceptibility to Type A backward pattern masking among hypothetically psychosis-prone college students.

Evaluated the Type A backward masking functions of individuals defined as vulnerable to psychosis by their scores on psychosis-proneness scales developed by L. J. Chapman et al (see record 1982-20120-001). An initial screening battery consisting of the MMPI and the Chapman scales was administered to 455 undergraduates. 10 Ss identified as belonging to a physical anhedonia group and 10 Ss with a perceptual aberration-magical ideation (per-mag) were compared with 10 normal control Ss on the visual masking task. Two dependent measures were evaluated: critical stimulus duration (CSD) in a no-mask condition and mean target identification as a function of varying interstimulus intervals. No differences were obtained in CSD values among groups. However, both psychosis-prone groups had significantly fewer correct identifications of target stimuli than did control Ss on the masking portion of the study. Results are discussed in terms of susceptibility to Type A backward masking as a potential marker of vulnerability to schizophrenia and in terms of the validity of the Chapman scales as measures of psychosis proneness. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masking and visual field effects on a lateralized rod-and-frame test.

Investigated whether laterality effects would be affected by poststimulus masking in a rod-and-frame test in which visual stimuli were presented to one side or the other of a central fixation point. 96 Ss (aged 18–28 yrs; 50% female) participated. For half the Ss, stimuli were followed by a blank screen; for the other half, stimuli were followed by a mask. An overall left visual field advantage (LVFA) was found in the task. An interaction of sex of Ss, masking conditions, and frame tilt was also found. Data showed that the sex by angle of frame interaction was significant when a mask was presented after the stimuli, but not when no mask followed the stimuli. Results suggest that the LVFA was only significant when a mask was presented after the stimuli. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual hemifield differences in the perception of letters and contour orientation.

In Exp. I, 10 students were required to recognize capital English letters presented 3– to the left or to the right of a fixation point. In Exp. II, 8 Ss were required to discriminate the orientation of a line presented in either the left or the right visual hemifield. In both experiments Ss displayed a significant right visual hemifield superiority, and a marked positive correlation was observed in the hemifield differences between the 2 recognition tasks. Results suggest that for certain classes of stimuli visual laterality differences may be subserved by a selective contour-tuning mechanism. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric changes in information processing during development.

Hemispheric processing of visually presented words and pictures was examined in 3 groups of Ss with mean ages of 8 yrs 8 mo, 12 yrs 3 mo, and 27 yrs 9 mo (154 Ss). Pictorial or symbolic stimuli were presented singly to either the right or left visual hemifield. Ss had to decide whether the 1st stimulus in a pair matched the 2nd stimulus. The major results were that (a) age groups differed in the strength of lateral differences, and (b) for all age groups, the right hemisphere was significantly faster in processing unmatched stimuli. Results suggest that lateral specialization of the left hemisphere is not complete until adolescence and that over the age range tested, the left hemisphere becomes progressively more specialized for the processing of matched data. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in use of left–right visual cues: A reexamination of mirror-image confusions in preschoolers.

Developed and tested a model that views left–right mirror-image confusions in preschoolers as part of a general difficulty in distinguishing left–right visual cues. It is proposed that left–right development occurs in 3 distinct levels: Level 1 preschoolers have difficulty responding consistently to left–right cues in their visual field; Level 2 children are capable of noticing but need instructions directing their attention to the relevant information; and Level 3 preschoolers spontaneously attend to these cues. In this study, 38 3- and 4-yr-olds' responses to left–right visual cues were evaluated on ability to distinguish left–right mirror-images of objects on a memory task and also on ability to name rows of objects on a page in a consistent lateral direction. Both abilities were assessed, first, without specific instructions on the relevance of left–right information and then with instructions. Ss were divided into 3 subgroups: spontaneous responders (Level 3), instructed learners, (Level 2), and nonlearners (Level 1). As predicted Ss generally performed at the same level for both left–right problems. Thus, levels of mirror-image ability reflect a broader developmental sequence. Confounding effects of general ability are unlikely to account for this, because correlation between left–right problems remained high (.62) when IQ effects were removed. Sharp age differences occurred, and a longitudinal follow-up showed Level 1 3-yr-olds performing at Level 2 for both tasks when retrained after 6–20 mo. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Unconscious anxiety": Phobic responses to masked stimuli.

Tested the hypothesis that an unconscious preattentive perceptual analysis of phobic stimuli is sufficient to elicit human fear responses. Selected snake- and spider-fearful Ss, as well as normal controls, were exposed to pictures of snakes, spiders, flowers, and mushrooms. A separate forced-choice recognition experiment established backward masking conditions that effectively precluded recognition of experimental stimuli both for fearful and nonfearful Ss. In the main experiment, these conditions were used to compare skin conductance responses (SCRs) to masked and nonmasked phobic and control pictures among fearful and nonfearful Ss. In support of the hypotheses, snake- and spider-fearful Ss showed elevated SCRs to snake and spider pictures as compared with neutral pictures and with responses of the nonfearful Ss under both masking conditions. Ratings of valence, arousal, and dominance indicated that the fearful Ss felt more negative, more aroused, and less dominant in relation to both masked and nonmasked phobic stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Locus of presentation and the selective masking effect.

Obtained forward and backward masking functions for 4 adult Ss in a nonmetacontrast letter recognition paradigm for letters presented either foveally or 1.75. in the periphery with a patterned mask. Both forward and backward masking were greater for peripherally presented stimuli. Forward masking showed a greater sensitivity to locus of presentation than backward masking. Results are considered in relation to the "ends-first" processing strategy explanation of the selective masking effect proposed by P. M. Merikle, et al. (French summary) (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantics at a glance: Is the right hemisphere special?

32 undergraduate Ss made an odd/even judgment to a single lateralized logograph, an Arabic numeral. All Ss were right-handed and had normal or corrected-to-normal vision. Stimuli were computer generated; Ss were shown the 8 Arabic numerals used by D. Besner et al (1986). Each S was tested with 1 block for each response hand. Data suggest that the left and right hemispheres are equally efficient at extracting meaning from at least some simple, highly familiar logographs. Particularly notable are the consistent reaction time (RT) differences between the left visual field and right visual field conditions for each response hand condition. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral asymmetry and hypnosis: A signal-detection analysis of divided visual field stimulation.

Examined brightness discriminations in a divided-field paradigm with a signal-detection procedure in 3 sessions, the 2nd with hypnosis. Practiced, hypnotically susceptible Ss were subdivided into high (n?=?6) and medium (n?=?5) susceptible groups on the basis of a susceptibility scale monitored throughout the hypnosis session. High-susceptible Ss showed increases in d′ in the left visual field (right hemisphere) with hypnosis, whereas medium-susceptible Ss showed bilateral enhancements. Beta remained invariant in both groups across 3 sessions but was higher in the left visual field. Results provide evidence of altered brain function with hypnosis and an association of focal right hemispheric changes with high susceptibility and, through the invariance of β, fail to support the attribution of perceptual changes to attitudinal, nonstate factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial localization in left and right visual fields.

Presented a series of single dots tachistoscopically in either the left or the right visual field, Ss task being to locate the dot on a spatial map depicting all of the lot locations presented. 7 experiments were carried out with 232 right-handed male and female undergraduates. For men, localization of the dot was more accurate in the left than in the right visual field, under all testing conditions. Women showed the left-field superiority under some testing conditions; under others they showed no difference between fields. There was no sex difference in over-all accuracy of performance, and simple detection of a dot was not more accurate in 1 field than another for either sex. Results are discussed in terms of a probable "spatial coordinate" system in the right hemisphere of the brain. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Psychopathy and laterality of cerebral function.

Used a tachistoscopic recognition task to test the hypothesis that psychopathy is associated with dysfunction of the dominant hemisphere. 55 prison inmates were divided into groups with high, medium, and low ratings of psychopathy. Ss were required to identify 3-letter words presented in a vertical arrangement either in the left visual half field (LVF) or the right visual half field (RVF) 1.5° from a central fixation point. Each of 24 words was presented twice, once in each visual half field, at an exposure time of 80 msec. The exposure time was then shortened to 40 msec, and a 2nd set of 24 words was presented twice, once in each visual half field. In general, words presented in the RVF were more readily identified than those presented in the LVF. There was no evidence that psychopathy was associated with any deficit in RVF performance even when handedness and writing position were taken into account. Further, based on responses to a laterality questionnaire, there were no group differences in "left-sidedness." Results do not support the hypothesis of dominant hemisphere dysfunction in psychopathy. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemisphere-specific interference in dichotic listening: Task variables and individual differences.

In Exps I and II, 214 right-handed college students were required to identify dichotically presented CV syllables with either no concurrent memory (CM) load or with a CM load of 6 low-imagery nouns. Based on performance on their initial set of no-load trials, Ss were assigned to either a right-, left-, or no-ear advantage (REA, LEA, or NEA) group. Results for the REA group were similar to the results of previous studies of visual laterality and concurrent activity: Introducing a CM load of 6 words reduced recognition of right-ear CVs but not left-ear CVs. Furthermore, these effects persisted across 2 blocks of no-load and memory-load trials. This Memory Load?×?Ear interaction was weaker in the NEA group and tended to be reversed in the LEA group. About 10% of Ss showed a consistent LEA for CV recognition, and, for these Ss, introducing a CM load of 6 words reduced recognition of left-ear CVs but did not change the recognition of right-ear CVs. Again, these effects persisted across 2 blocks of no-load and memory load trials. Exp III (48 Ss) was similar to Exps I and II except that the CM task involved nonsense shapes that could probably be processed by either hemisphere. Introducing this concurrent nonverbal memory task did not reduce the recognition of either right- or left-ear CVs. Results indicate that the verbal nature of the concurrent task appears to be critical, as in previous visual laterality experiments. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Midline and lateral field sound localization in the albino rat (Rattus norvegicus).

Estimated the normal sensory capacity of 6 albino Sprague-Dawley rats for sound localization in the lateral fields and related this ability to the effects of brain damage on sound localization, as demonstrated in previous studies. Each of the Ss performed at high levels on a midline task but had great difficulty with tests in the left and right fields. Minimum audible angles for midline localization were obtained for 2 Ss and were estimated as 11.5° and 13.5°. Performance levels on the hemifield tests for each of the 6 Ss, however, were too low to permit estimates of threshold even with speakers separated by 60°. It is suggested that for animals that do not have the capacity for detailed sound localization, subcortical mechanisms may be sufficient. For animals that do have the ability to resolve multiple positions in the horizontal plane, auditory cortex may be essential for both lateral field and midline localization. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential hemispheric processing of faces: Methodological considerations and reinterpretation.

Examines the procedures and stimuli (physiognomies) used in lateralized face recognition experiments with normal Ss, as well as in related perceptual and identification experiments. Results reveal that in general a left visual field (right hemisphere) advantage is obtained when: (a) stimulus information is degraded; (b) faces to be compared are highly discriminable; (c) set of unfamiliar faces is used; and (d) task requirements allow a lax criterion of recognition. These conditions seem to make holistic processing adequate for the task; if the conditions require analytic judgments, then a right visual field (left hemisphere) advantage may be obtained. Thus, no hemifield has an inherent or absolute advantage and these procedural conditions may critically determine what hemifield advantage is observed in any given experiment with faces (or other types of stimuli). Apparently, both hemispheres may contribute to the processing of faces but their contributions vary as a function of task demands. A right hemisphere advantage may reflect an enhanced role of the processes of configuration, completion, categorization, or set. A left hemisphere advantage need not involve the language function but it may reflect a genuine visuospatial contribution. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of cross-modal recognition in infant pigtail monkeys (Macaca nemestrina).

Examined the development of cross-modal recognition in 48 infant pigtail monkeys in 2 studies by using an adaptation of the visual preference technique. Ss were first familiarized orally with pacifiers of 1 of 2 shapes and were then tested on corresponding visual stimuli. In a cross-sectional experiment (Exp I), Ss under 200 days postconception at test (approximately 4 postnatal weeks) showed a visual preference for the orally familiar stimuli, which provided evidence for cross-modal recognition. Ss over 200 days postconception at test showed a visual preference for 1 of the test stimuli, which made their data uninterpretable with respect to cross-modal abilities. In a longitudinal experiment (Exp II), Ss were tested once when they were younger than 200 days postconception and once when they were older. When young, they showed a visual preference for the orally familiar stimuli. When older, they showed a visual preference for the same test stimuli found for the cross-sectional Ss. Results are discussed relative to human infant cross-modal data obtained by similar procedures. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)