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Results for “Perceptual Distortion”

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At least 847 records · Page 47Linked to original sources
PubMed1991

Evaluation of a dereverberation technique.

A two-microphone dereverberation technique was evaluated by obtaining speech recognition measures and preference judgments from normal-hearing and hearing-impaired listeners. Monaural speech recognition performance was measured for two reverberation conditions (0.4 second and 1.2 seconds) with and without processing. Binaural speech recognition performance was also measured for the unprocessed conditions. In addition, paired-comparison judgments of preference were obtained for all combinations of the processed and unprocessed monaural stimuli. For both groups of subjects, scores at the shorter reverberation time were significantly higher than scores for the longer reverberation time. For the normal-hearing subjects, processing to dereverberate had no significant effect on speech recognition performance. Binaural presentation of the unprocessed signal yielded significantly higher scores. For the hearing-impaired subjects, performance was significantly better in the unprocessed condition than the processed condition, but was not significantly different from the binaural condition. Paired-comparison judgments revealed differences in patterns of preference between normal-hearing and hearing-impaired listeners.

Adult↗
PubMed1984

The effect of familial sinistrality on perceptual learning.

Perceptual learning as measured by adaptation to prismatically displaced vision was contrasted in groups of familial sinistral (FS) and familial dextral (FD), strongly right-handed adult females. The FS group exhibited significantly larger target pointing and eye positioning adjustments than the FD group. Further, only the FS group showed transfer of training from the hand used during prism viewing to the unobserved one.

Adult↗
PubMed1987

Effects of blurring and stimulus size on the lateralized processing of nonverbal stimuli.

Right-handed subjects indicated whether two novel, nonlinguistic stimuli were physically identical or not. In Experiment 1 blurring these stimuli impaired performance when stimuli were projected to the right visual field but not when stimuli were projected to the left visual field. This lateralized effect of blurring is similar to earlier findings in letter-matching experiments and indicates that such effects do not depend on hemispheric differences in verbal mediation. Experiment 2 examined the lateralized effects of stimulus size using the same task as Experiment 1. The pattern of results from this experiment suggests that both visual spatial frequency and stimulus perceptibility contribute to interactions of stimulus clarity and visual field and that neither factor by itself may be the sole determinant of the lateralized effects of input variables.

Adult↗
PubMed1990

Effects of luminance and blur on hemispheric asymmetries in temporal integration.

A task involving temporal integration of form was employed to examine the effects of input characteristics on hemispheric asymmetries. In Experiment 1, decreases in luminance produced greater improvement of right hemisphere (RH) performance. In Experiment 2, dioptric blur produced greater impairment of left hemisphere (LH) performance. The results suggest that spatial frequencies below nine cycles per degree are processed more efficiently in the RH. In Experiment 3, effects of input characteristics on hemispheric asymmetry were found to be dependent on the spatial frequencies required for processing by task demands, as mediated by interflash interval (IFI) duration. Increased blur produced greater impairment of LH performance at short IFI duration; at a longer IFI duration, however, increased blur produced equal impairment of RH and LH performance.

Adult↗
PubMed1990

Facial neglect.

Following a stroke, a retired industrial chemist, K.L., complained that faces looked "different" and had become difficult to recognize. Investigation of this problem revealed that it particularly affected the left half of a face as seen by K.L. Defective recognition of this (left) half was found for normal faces, chimaeric faces, and for half-faces presented in isolation, whether upright or inverted. The problem was apparent for both internal and external facial features. Further studies with chimaeric faces demonstrated inattention to left-side features in K.L.'s judgements of facial expression and of resemblance between faces. Moreover, the left-half of a chimaeric face was affected even when it was itself forming part of the face positioned on the right in a display of two horizontally aligned chimaerics. K.L.'s spatial contrast sensitivity function was within normal limits for his age. He did not experience differential difficulty in recognizing the left side of everyday objects or of car-fronts (another stimulus class demanding within-category discrimination between visually similar items that display approximate left-right symmetry). He was also able to sort left or right half-stimuli correctly into the categories "human face", "dog face", or "tree". Although K.L. had a left visual field defect, the problem with faces occurred within otherwise intact parts of his field of vision. We suggest that his disorder can be considered a domain-specific form of unilateral neglect.

Aged↗
PubMed1990

Prism adaptation and other tasks involving spatial abilities in patients with Parkinson's disease, patients with frontal lobe lesions and patients with unilateral temporal lobectomies.

Patients in the early stages of Parkinson's disease were compared with patients who had sustained damage specific to either the frontal or temporal lobes and normal controls on a delayed alternation task, a test of the left right orientation and a prism adaptation task. On the former two tasks age accounted for more of the variability in performance than did site of brain lesion. However, patients with frontal lobe, right temporal lobe or basal ganglia damage were significantly impaired on the adaptation task. The results are discussed with regard to "switching", "sequencing" and "internal guidance" of movement hypotheses.

Adult↗