Right visual field superiority for letter recognition with partial report.

Experiments using partial report techniques have typically failed to find left-right visual field differences in the recognition of tachistoscopically presented letter rows. Such data represent a difficulty for theories that emphasize the relevance of cerebral hemispheric asymmetry. It is contended that the end items of a display are critical, and that a truly symmetric display should have both a left and a right end item in each visual field. In the present experiments with 36 righthanded university students, partial report procedures were employed, but a gap was placed between the left and right halves of the display. In the 1st experiment, a single-letter spatial probe procedure was used, and a clear right visual field superiority was found. In the 2nd experiment, a hemifield report procedure was used; the presence of a gap in the display enhanced the right visual field superiority, especially for shorter strings of letters. Results indicate that right visual field superiority can be obtained with partial report procedures under appropriate conditions. (French summary) (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right hemisphere language: Remaining problems.

Responds to J. J. Myers's (1984) critique of the present author's (see record 1984-07149-001) assertion that the incidence of right-hemisphere language (RHL) capacity is relatively infrequent in human split-brain cases (SBCs). The following areas of Myers's concerns are addressed: (1) the demographics of RHL, (2) neurologic criteria for considering a commissurotomy patient worthy of study, and (3) the suitability of considering patients with explicit sparing of the anterior commissure as SBCs. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form-specific visual priming in the right cerebral hemisphere.

Results of 4 experiments indicate that both within-modality and case-specific visual priming for words are greater when test stimuli are presented initially to the right cerebral hemisphere (RH). In contrast, neither within-modality nor case-specific explicit memory for words is greater when stimuli are presented initially to the RH. Priming is measured using word-stem completion, and explicit memory is measured using word-stem cued recall. In both cases, Ss first rate how much they like words, and then word stems are presented briefly to the RH (in the left visual field) or to the left hemisphere (in the right visual field). Results suggest that at least 2 separate systems encode the visual representations that produce priming. The system that is more effective in the RH is better at representing form-specific information, whereas another system that is not more effective in the RH does not distinguish among distinct instances of word forms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inversion superiority in visual agnosia may be common to a variety of orientation polarised objects besides faces

Selective impairment in recognition of faces (prosopagnosia) resulting from certain localized cortical lesions has been advanced as an argument for a face specific brain module. The argument is claimed to be strengthened by the discovery of an inversion superiority effect in the recognition of faces by a prosopagnosic patient (Farah et al., Vis Res 1995b;35:2089-2093). The present paper reports an inversion superiority effect in the recognition of faces and shoes in a visual agnosic patient. The finding raises the possibility that several classes of orientationally polarized objects, of which shoes and faces are examples, will exhibit inversion superiority.     

Probability matching in visual selective attention.

J. Jonides (see record 1981-22746-001) suggested a model to account for shifts of spatial attention in visual search tasks with less than 100% cue validity. This 2-stage probability matching model was subsequently tested by Jonides (see record 1984-08558-001). Reaction time (RT) distribution characteristics provided some support for the model. The present author reanalyzes Jonides's data (including that published in 1981). Analysis showed strong support for the probability matching hypothesis. It is concluded that probability matching is an important strategic characteristic of visual spatial attention. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decision processes in visual discrimination of line orientation.

The contribution of decision factors to the meridional variations in line orientation discrimination (OD) was determined for 2-alternative forced-choice experimental designs. With K. O. Johnson's (1980) formalization of decision processes in discrimination tasks, 3 decision factors were identified: decision rule, memory variance, and criterial noise. Exp I (with 13 Ss) showed the effect of experimental design on OD to be similar at horizontal and oblique standard orientations, indicating that the meridional variations in OD were not due to a decision rule anisotropy. In Exp II (with 5 Ss) the effect of the interstimulus interval was also found to be similar at both standard orientations, suggesting that the memory variance is isotropic in the orientation domain. Exps III and IV (with a total of 7 Ss) supported the hypothesis that the meridional variations in OD are not due to a criterial noise anisotropy. Results strongly suggest that the oblique effect in OD is due to sensorial factors rather than to decision factors. Therefore, they further support the hypothesis linking the anisotropy of the preferred orientation distribution of Area 17-S cells (a single physiologically defined class of cells in the primary visual cortex) and the meridional variations in OD. (58 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delayed matching performance after visual Wulst lesions in pigeons.

Eight homing pigeons were trained preoperatively on a mixed delayed matching-to-sample (DMTS) task in which 6 different conditions were presented randomly: simultaneous matching and 0-, 1-, 2-, 4-, and 8-sec delays. Ss that sustained extensive or complete damage to the visual Wulst, a multilaminate region in the pigeon telencephalon which occupies the dorsal aspect of the cerebral hemisphere, and moderate damage to the hyperstriatum ventrale showed a decrease in accuracy of performance to chance levels in all of the delay conditions as well as in simultaneous matching. After extensive retraining on the 0-sec-delay matching alone, performance on 0-sec-delay and simultaneous matching, presented in mixed DMTS, improved to between 70 and 90% correct. However, performance on delay conditions remained at chance level. All but 1 S failed to show signs of postoperative improvement on delay problems in the course of the final testing. Data suggest that the conditional property of the task was a critical factor in the initial drop in accuracy on all of the presented problems. The relatively permanent loss of accuracy on all delay conditions is attributed mainly to the temporal separation of sample and comparison stimuli. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right hemisphere language following brain bisection: A 20-year perspective.

Reviews studies on 3 series of patients who underwent brain bisection. A review of right-hemisphere language in split-brain patients suggests that it occurs infrequently. When present in these patients, right-hemisphere linguistic competence ranges from simple comprehensive skills to a system that can both recognize written and spoke language and produce speech. In almost all cases, the existence of right-hemisphere language is attributable to early left-hemisphere brain damage. Such patients prove valuable for the study of global mechanisms of mind, such as those underlying the sense of conscious unity. These studies indicate that subjective awareness arises out of the dominant left hemisphere's unrelenting need to explain actions from a multitude of mental systems. Second, a half-brain system does not seem to be cognitively sophisticated without language despite certain visual-spatial skills. Third, the awareness that the 2 cognitive systems interact at important levels in attentional process and semantics suggests that a variety of subcallosal brain mechanisms may be involved. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right hemisphere language: Science or fiction?

Reviews inconsistencies and misrepresentations in M. S. Gazzaniga's (see record 1984-07149-001) analysis of 3 series of patients who underwent brain bisection. The inaccuracies led to the conclusion that right-hemisphere (RH) language and cognition are a rarity attributable to left-hemisphere brain damage. Gazzaniga's data fail to make a substantive contribution to the understanding of RH language or cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of categorization in visual search for orientation.

Visual search for 1 target orientation is fast and virtually independent of set size if all of the distractors are of a single, different orientation. However, in the presence of distractors of several orientations, search can become inefficient and strongly dependent on set size (Exp 1). Search can be inefficient even if only 2 distractor orientations are used and even if those orientations are quite remote from the target orientation (e.g., 20° or even 40° away, Exp 2). Search for 1 orientation among heterogeneous distractor orientations becomes more efficient if the target orientation is the only item possessing a categorical attribute such as steep, shallow (Exp 3), tilted left or tilted right (Exp 4), or simply tilted (Exps 5 and 6). Orientation categories appear to be 1 of several strategies used in visual search for orientation. These serve as a compromise between the limits on parallel visual processing and the demands of a complex visual world. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right hemisphere emotional perception: evidence across multiple channels

Emotional perception was examined in stroke patients across 3 communication channels: facial, prosodic, and lexical. Hemispheric specialization for emotion was tested via right-hemisphere (RH) and valence hypotheses, and relationships among channels were determined. Participants were 11 right-brain-damaged (RBD), 10 left-brain-damaged (LBD), and 15 demographically matched normal control (NC) adults. Experimental measures, with analogous psychometric properties, were identification and discrimination tasks, including a range of positive and negative emotions. Nonemotional control tasks were used for each channel. For identification, RBDs were significantly impaired relative to LBDs and NCs across channels and valences, supporting the RH hypothesis. No group differences emerged for discrimination. Findings were not influenced by demographic, clinical, or control variables. Correlations among the channels were more prominent for normal than for brain-damaged groups.     

Local and global orientation in visual search

Six experiments investigated the role of global (shape) and local (contour) orientation in visual search for an orientation target. Experiment 1 demonstrated that search for a conjunction of local contours with a distinct global orientation was less efficient than search for a target featurally distinct in terms of both global and local contour orientation. However, Experiments 2 and 4 demonstrated that the presence of a unique line contour was neither sufficient nor necessary to allow efficient search. Experiment 5 found that search for a local orientation difference was strongly impeded by irrelevant variation in global orientation, arguing for a preeminent role for global orientation. Finally, Experiment 6 demonstrated that the orientation search asymmetry holds for the global orientation of stimuli. Taken together, the results are consistent with visual search processes guided predominantly by a representation of global orientation.     

Cross-modal equivalence in early infancy: Auditory–visual intensity matching.

To examine the hypothesis that young infants ignore differences between lights and sounds and instead respond to auditory and visual stimuli as more or less similar depending on their intensity, a cardiac habituation/dishabituation method with a test for stimulus generalization was employed. In 2 experiments, a total of 40 3-wk-old Ss were repeatedly presented with white-light followed by white-noise stimuli of different intensities. A U-shaped relationship between magnitude of cardiac response (CR) and loudness was found. In view of previous findings that without prior visual stimulation a monotonic increase in CR to the same range of auditory stimuli results, this finding of a significant quadratic relationship with loudness suggests that Ss were responding to the auditory stimuli in terms of their similarity to the previously presented visual stimulus. A separate group of 14 infants presented with a more intense visual stimulus exhibited a shift in the intensity at which a minimal CR occurred. Results of a study with 31 adults did not show any systematic relationship between CR and loudness, indicating that unlike infants, adults do not spontaneously make cross-modal matches of intensity. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of gravitational cues on visual search for orientation.

To determine whether nonvisual (vestibular and somatosensory) information participates in low-level orientation processing, Ss in different postural conditions (upright, supine, and sitting immobilized) searched for a target distinguishable from distractors by differences in orientation (A. Treisman's [1985] "pop-out" paradigm). Searches for vertical and horizontal targets were dramatically modified as a function of the postural position, indicating that the processing of orientation in early vision is not only retinal but integrates information from the sensory graviceptors. This visuovestibular phenomenon is interpreted in the conceptual framework of D. H. Foster and P. A. Ward's (1991) model based on local orthogonal orientation filters and T. A. Stoffregen and G. E. Riccio's (1988) dynamics of balance theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemisphere dysfunction and left hemisphere overactivation in schizophrenia.

Reports 2 experiments relating schizophrenia to functional brain asymmetry. In Exp I, 24 schizophrenics (mean age, 30.8 yrs) were compared to 24 matched controls (mean age, 37.3 yrs) on 2 tachistoscopic tasks (Syllable Test and Dot Location Test) designed to measure verbal and spatial information processing in the 2 hemispheres. Unlike the controls, the schizophrenics showed a right hemisphere superiority both on the verbal and on the spatial tests, indicating left hemisphere dysfunction in the initial processing of verbal information. In Exp II, lateral eye movements, as an index of contralateral hemispheric activation, were measured in a group of 24 paranoid schizophrenics (mean age, 28.9 yrs), 24 nonparanoid schizophrenics (mean age, 32.7 yrs), and 24 matched controls (mean age, 31.2 yrs). The eye movements were elicited by presenting the Ss with verbal neutral, verbal emotional, spatial neutral, and spatial emotional questions. The schizophrenics had significantly more rightward eye movement, compared to controls, regardless of question type, indicating left hemisphere overactivation. Results suggest that schizophrenia is associated with a pattern consisting of both left hemisphere dysfunction and overactivation. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversing visual search asymmetries with conjunctions of movement and orientation.

Many theories of visual search offer general principles intended to apply to search for targets defined by any stimulus attribute. The importance of considering specific properties of different visual subsystems is demonstrated by examining search for movement–orientation conjunctions. In displays of intermingled moving and stationary stimuli, search for a salient tilted target (45° vs vertical) is easier among moving than stationary stimuli. If a finer orientation distinction is required (9° vs vertical), the reverse is true; search is easier among the stationary. This follows from the known properties of visual subsystems specialized for processing moving or stationary stimuli. It is not predicted by general theories of visual search such as guided search or similarity theory, nor by principles of Gestalt grouping. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of orientation on the identification of simple visual patterns.

Two experiments, with 16 university students, revealed that errors of identification for alphanumeric characters increased approximately linearly with increased angular deviation from the standard upright orientation. Thus, pattern recognition does not seem to proceed via the extraction of "orientation-invariant features." It is argued that prior failures to discover systematic effects of orientation on the identification of simple patterns may have resulted from the use of RT as a dependent measure. Based on the data from Exp II, it was estimated that as little as 15 msec of processing time may have been sufficient to compensate fully for a 180° rotation of a simple pattern in the present experimental situation. Thus, RT experiments seeking effects of orientation must be designated to detect effects of smaller magnitude than may have been previously anticipated. (French abstract) (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Display density influences visual search for conjunctions of movement and orientation.

J. Driver and P. McLeod (1992) reported that the ease of visual search for targets defined by a conjunction of movement and orientation was affected by an interaction between target movement and target-nontarget discriminability. When the orientation discrimination to distinguish target from nontarget was difficult, stationary targets were easier to find than moving targets. But when the orientation discrimination to distinguish target from nontarget was easy, moving targets were easier to find than stationary targets. H. J. Muller and J. Maxwell (1994) repeated the experiment but failed to find the interaction. The authors show that the difference between these results was due to the density of the visual displays used. With a high-density display, the authors replicate Driver and McLeod's result; with a low-density display, they replicate Muller and Maxwell's result. (PsycINFO Database Record (c) 2010 APA, all rights reserved)