平滑运动条件下的图形颜色及形状加工特性的研究

本研究对在运动图形识别过程中,有关图形的不同特征（颜色、形状等）的加工特性、方向性效应以及不同空间位置（或时间间隔）对图形识别的影响了探讨。结果发现,视觉系统在运动信息加工时,对目标的不同特征的加工存在不均衡性,加工的难度有差异。颜色的加工难度要比形状的加工难度小。视觉系统对不同运动方向上的图形匹配反应特性也存在差异,图形匹配过程受时间或距离因素的影响,匹配的反应时随着两个比较图形之间的空间距离的增加而减少。     

VISUAL IDENTITY MATCHING AND AUDITORY-VISUAL MATCHING: A PROCEDURAL NOTE

After preliminary computerized training on visual-visual identity matching, a 5-year-old boy with autism (Sam) was given visual-visual and auditory-visual matching-to-sample tests with new stimuli. He did well in matching dictated name samples to 20 pictures, 26 printed upper case letters, and 9 single-digit numbers. In matching the visual stimuli (pictures, letters, or numbers) to themselves, however, he did not perform well. We then increased the number of picture comparisons per trial from two to three. In tests after this three-comparison training, Sam correctly matched on 95% of the original 20-stimulus, four-comparison, identity-matching test trials. He went on to demonstrate accurate identity matching of the numbers, letters, and new pictures. In identity-matching tests on the table top, he performed poorly until the stimulus array was made to resemble the stimulus arrangement on the computer. These findings showed that seemingly small procedural changes can influence performance and demonstrated that successful auditory-visual matching does not guarantee proficiency in visual-visual identity matching.     

Attention to local form information can prevent access to semantic information.

Humphreys and Boucart (1997) have shown that when processing of local form is required for response, surrounding global information is automatically processed to a semantic level. The generality of this effect was investigated in two experiments in which the perceptual load of the relevant local form information was manipulated, as was uncertainty about perceptual load. Participants attended to a single line segment inside a picture of an animal or a vehicle and then decided which of two pictures in the target/distractor display that followed contained a line segment that matched the first in orientation. The perceptual load of the relevant local form information was either low (the matching line segment was one of the solitary line segments presented in the centre ofthe target and distractor pictures), or high (the matching line segment was part of one of the solitary letters presented in the centre of the target and distractor pictures). The semantic relations among the pictures were manipulated, and when perceptual load remained constant across trials, semantic relations affected performance in the low-load but not in the high-load condition. When perceptual load varied from trial to trial, there was no evidence of any semantic processing on either low- or high-load trials. The results suggest that in form-matching tasks, attentional priority can be given to local information, thus preventing access to semantic information derived from global shape. They further suggest that the distribution of attention is not dictated entirely by the actual perceptual demands of the relevant stimulus, indicating an important role for top-down processing.     

Dysnomia in Alzheimer's disease: an evaluation of neurobehavioral subtypes.

The relative influence of perceptual and semantic features on naming performance was investigated with reference to the neurobehavioral profiles displayed by patients with Alzheimer's disease (AD). Forty-one patients were classified as manifesting a verbal, visual, or global subtype based upon their pattern of neuropsychological functioning. Perceptual characteristics of to-be-named pictures were varied by manipulating the amount of line detail, whereas semantic qualities were varied by altering word frequency norms. All AD subtypes were less accurate than normal elderly controls in naming low frequency pictures. Patients and controls took longer to name low frequency and high complexity pictures, and this effect was comparable across the AD groups. Patients with predominantly visual deficits were significantly slower in naming than controls, and those with verbal impairments made a higher proportion of semantic naming errors when compared to patients displaying visual or severe global impairments. These results suggest that deficits in semantic processing contribute to naming dysfunction in AD, and they highlight the importance of examining dissociations among neurobehavioral subtypes.     

Identification confusions among letters of the alphabet

Black, uppercase letters, subtending 6.0' of arc in height, were presented tachistoscopically to 6 subjects. An exposure duration was chosen to keep the subject's identification performance at about 50% correct. On each trial a single letter was presented, and the subject was required to identify the letter by verbal response. The resulting 26 X 26 confusion matrix was based on 3,900 trials (150 trials per letter). Several models of visual processing were used to generate predicted confusions among letter pairs. Models based on template overlap, geometric features, and two-dimensional spatial frequency content (Fourier transforms) were tested. The highest correlation (.70) between actual and predicted confusions was attained by the model based on the Fourier transformed letters filtered by the human contrast sensitivity function. These results demonstrate that the spatial frequency content of visual patterns can provide a valuable metric for predicting their psychological similarity. The results further suggest that spatial frequency models of visual processing are competitive with feature analysis models.     

Useful visual field size for pattern perception

The useful visual field size at each fixation in a pattern was investigated by artificially supplying various visual field sizes on a TV display. The degree of pattern perception was measured in terms of recognition memory for pictures, and the speed of processing pictures was determined as a function of field size. A serious deterioration in the perception of pictures occurred as the visual field was limited to a small area around the fovea (about 3.3° × 3.3°), processing speed becoming extremely slow. Speed increased gradually as visual field size became larger, to reach a certain level beyond which no further increase was observed. The visual field size at this asymptotic speed was called the useful visual field and was found to be about 50% of the entire pattern size. Analysis of eye-movement records demonstrated that in terms of the useful visual field, the scanning characteristics of the eye over the pattern occurred in a heavily overlapping manner to assure good perception of the pattern.     

Covert reading of letters in a case of global alexia

This study describes the case of a global alexic patient with a severe reading deficit affecting words, letters and Arabic numbers, following a left posterior lesion. The patient (VA) could not match spoken letters to their graphic form. A preserved ability to recognize shape and canonical orientation of letters indicates intact access to the representation of letters and numbers as visual objects. A relatively preserved ability to match lowercase to uppercase letters suggests partially spared access to abstract letter identities independently of their visual forms. The patient was also unable to match spoken letters and numbers to their visual form, indicating that she could not access the graphemic representations of letters from their phonological representations. This pattern of performance suggests that the link between graphemic and phonological representations is disrupted in this patient. We hypothesize that VA’ residual reading abilities are supported by the right hemisphere.     

The Role of Stimulus Type and Semantic Category‐Level Attentional Set in Sustained Inattentional Blindness

Abstract: We examined the effect of the stimulus type and semantic categorization of the unexpected stimulus on sustained Inattentional Blindness (IB). Results showed that observers could establish attentional set based on a higher level of semantic categorization, which tuned one's attention to prioritizing semantic content over others. The unexpected stimulus, congruent with the attended objects in semantic categorization, was more likely to be noticed, whereas the incongruent semantic stimulus seemed to be unseen. Semantic category‐level attentional set played a crucial role in breaking through IB. The semantically congruent Chinese characters stimulus was detected and recognized more often than a semantically congruent picture stimulus, indicating that Chinese characters had more power to attract attention to escape sustained IB than pictures involved in visual processing. Presumably the finding of Chinese characters breaking through IB more easily might be due to the fact that Chinese characters look more distinct from pictures, rather than Chinese characters being processed more easily. Further research should be taken to test the semantic processing efficiency between pictures and Chinese characters in sustained IB.     

Hemispheric asymmetry,early visual processes,and serial memory comparison

Observers indicated whether a single probe letter presented to the left visual field/right hemisphere (LVF-RH) or to the right visual field/left hemisphere (RVF-LH) matched one of two, three, four, or five set letters in both name and case. For positive trials during the initial experimental session, the slope of the linear memory set size reaction time function was increased by perceptually degrading the probe letter on LVF-RH trials, but not on RVF-LH trials. In addition, perceptual degradation of the probe letter increased the intercept of the memory set size function more on RVF-LH trials than on LVF-RH trials. During subsequent experimental sessions, the same pattern of intercept results was obtained but perceptual degradation of the probe no longer changed the slope for either LVF-RH or RVF-LH trials. However, the slopes were uniformly lower on RVF-LH trials than on LVF-RH trials. The major results are consistent with hypothesized right-hemisphere efficiency for early processing stages and left-hemisphere efficiency for serial processing of alphanumeric information. The results further illustrate the importance of separating stages of processing in studies of cerebral laterality and indicate that the relative difficulty of the various stages can be a determinant of laterality results.     

Levels of processing in disruptive effects of prior information

Under certain conditions, advance information about possible letter alternatives may depress recognition of single tachistoscopically presented letters followed by a pattern mask. Neill and Walling (1981) found that this “before-disruption effect” occurred specifically when alternatives were featurally similar. In contrast, Experiment 1 of the present study found that precuing facilitated identification of unfamiliar stimuli composed of letterlike features, particularly when alternatives differed in only one critical feature. Contrary to Smith, Haviland, Reder, Brownell, and Adams (1976), composition of letterlike features is therefore not sufficient to produce the before-disruption effect. The before-disruption effect appears to occur when there is opportunity to represent the stimulus at a deeper (i.e., name) level, but foreknowledge of a critical distinguishing feature biases processing instead toward the level of physical features. Congruent with this analysis, Experiment 2 found the before-disruption effect for letters to be attenuated when targets were unpredictably upper- and lowercase, necessitating name-level matching to the alternatives. Experiment 3 found the superior identification of unprecued letters to be paradoxically associated with inferior target detection, as indicated by concurrent presence/absence judgments. In addition, identification of unprecued letters, but not precued letters, was significantly above chance on trials in which overt target detection failed to occur. The results are consistent with recent suggestions that pattern masking does not terminate perceptual processing, but rather interferes with conscious awareness of completed visual analysis.     

Evidence for direct visual access to letter identities

Subjects were presented with two letters from the set BCDFGHLNPORTVZ, one in upper case and one in lower case. Subjects were required to decide, as quickly as possible, whether the two letters on each trial were the same (e.g., Bb) or different (e.g., Bd). Because letters were always physically different, subjects presumably must name the letters in order to respond. Reaction times were predicted by the visual similarity of the letters, and not by their phonemic distinctive feature similarity. Consistent with previous work showing that a word's meaning can be assessed directly from visual information, the findings suggest that visual analysis of a capital or small letter can result in knowing the latter name without further linguistic processing. These results were interpreted as an example of automatic detection as described by Schneider and Shiffrin (1977).     

Crossmodal semantic priming by naturalistic sounds and spoken words enhances visual sensitivity

We propose a multisensory framework based on Glaser and Glaser's (1989) general reading-naming interference model to account for the semantic priming effect by naturalistic sounds and spoken words on visual picture sensitivity. Four experiments were designed to investigate two key issues: First, can auditory stimuli enhance visual sensitivity when the sound leads the picture as well as when they are presented simultaneously? And, second, do naturalistic sounds (e.g., a dog's "woofing") and spoken words (e.g., /d?g/) elicit similar semantic priming effects? Here, we estimated participants' sensitivity and response criterion using signal detection theory in a picture detection task. The results demonstrate that naturalistic sounds enhanced visual sensitivity when the onset of the sounds led that of the picture by 346 ms (but not when the sounds led the pictures by 173 ms, nor when they were presented simultaneously, Experiments 1-3A). At the same SOA, however, spoken words did not induce semantic priming effects on visual detection sensitivity (Experiments 3B and 4A). When using a dual picture detection/identification task, both kinds of auditory stimulus induced a similar semantic priming effect (Experiment 4B). Therefore, we suggest that there needs to be sufficient processing time for the auditory stimulus to access its associated meaning to modulate visual perception. Besides, the interactions between pictures and the two types of sounds depend not only on their processing route to access semantic representations, but also on the response to be made to fulfill the requirements of the task.     

Levels of processing and picture memory: the physical superiority effect

Six experiments studied the effect of physical orienting questions (e.g., "Is this angular?") and semantic orienting questions (e.g., "Is this edible?") on memory for unrelated pictures at stimulus durations ranging from 125-2,000 ms. Results ran contrary to the semantic superiority "rule of thumb," which is based primarily on verbal memory experiments. Physical questions were associated with better free recall and cued recall of a diverse set of visual scenes (Experiments 1, 2, and 4). This occurred both when general and highly specific semantic questions were used (Experiments 1 and 2). Similar results were obtained when more simplistic visual stimuli--photographs of single objects--were used (Experiments 5 and 6). As in the case of the semantic superiority effect with words, the physical superiority effect for pictures was eliminated or reversed when the same physical questions were repeated throughout the session (Experiments 4 and 6). Conflicts with results of previous levels of processing experiments with words and nonverbal stimuli (e.g., faces) are explained in terms of the sensory-semantic model (Nelson, Reed, & McEvoy, 1977). Implications for picture memory research and the levels of processing viewpoint are discussed.     

How to make the word-length effect disappear in letter-by-letter dyslexia: implications for an account of the disorder

The diagnosis of letter-by-letter (LBL) dyslexia is based on the observation of a substantial and monotonic increase of word naming latencies as the number of letters in the stimulus increases. This pattern of performance is typically interpreted as indicating that word recognition in LBL dyslexia depends on the sequential identification of individual letters. We show, in 7 LBL patients, that the word-length effect can be eliminated if words of different lengths are matched on the sum of the confusability (visual similarity between a letter and the remainder of the alphabet) of their constituent letters. Additional experiments demonstrate that this result is mediated by parallel letter processing and not by any compensatory serial processing strategy. These findings indicate that parallel processing contributes significantly to explicit word recognition in LBL dyslexia and that a letter-processing impairment is fundamental in causing the disorder.     

Neural Recruitment and CognitiveAging: Two Hemispheres Are Better Than One, Especially as You Age

Several neuroimaging studies have reported that older adults show weaker activations in some brain areas together with stronger activations in other areas, compared with younger adults performing the same task. This pattern may reflect neural recruitment that compensates for age-related neural declines. The recruitment hypothesis was tested in a visual laterality study that investigated age differences in the efficiency of bihemispheric processing. Letter-matching tasks of varying complexity were performed under two conditions: (a) matching letters projected to the same visual field (hemisphere) and (b) matching letters projected to opposite visual fields (hemispheres). As predicted by the recruitment hypothesis, older adults generally performed better in the bilateral than unilateral condition, whereas younger adults showed this pattern onlyfor the most complex task. We discuss the relation between these results and neuroimaging evidence for recruitment, and the relevance of the present bihemispheric advantage to other evidence for age-related changes in interhemispheric transfer.     

Object Recognition Difficulty in Visual Apperceptive Agnosia

Two patients with visual apperceptive agnosia were examined on tasks assessing the appreciation of visual material. Elementary visual functioning was relatively preserved, but they had profound difficulty recognizing and naming line drawings. More detailed evaluation revealed accurate recognition of regular geometric shapes and colors, but performance deteriorated when the shapes were made more complex visually, when multiple-choice arrays contained larger numbers of simple targets and foils, and when a mental manipulation such as a rotation was required. The recognition of letters and words was similarly compromised. Naming, recognition, and anomaly judgments of colored pictures and real objects were more accurate than similar decisions involving black-and-white line drawings. Visual imagery for shapes, letters, and objects appeared to be more accurate than visual perception of the same materials. We hypothesize that object recognition difficulty in visual apperceptive agnosia is due to two related factors: the impaired appreciation of the visual perceptual features that constitute objects, and a limitation in the cognitive resources that are available for processing demanding material within the visual modality.     

Semantic priming effects on picture and word processing

The effects of semantic priming on picture and word processing were assessed under conditions in which subjects were required simply to identify stimuli (label pictures or read words) as rapidly as possible. Stimuli were presented in pairs (a prime followed by a target), with half of the pairs containing members of the same semantic category and half containing unrelated concepts. Semantic relatedness was found to facilitate the identification of both pictures (Experiment 1) and words (Experiment 2), and obtained interactions of semantic relatedness and stimulus quality in both experiments suggested that semantic priming affects the initial encoding of both types of stimuli. In Experiment 3, subjects received pairs of pictures, pairs of words, and mixed pairs composed of a picture and a word or of a word and a picture. Significant priming effects were obtained on mixed as well as unmixed pairs, supporting the assumption that pictures and words access semantic information from a common semantic store. Of primary interest was the significantly greater priming obtained in picture-picture pairs than in word-word or mixed pairs. This suggests that, in addition to priming that is mediated by the semantic system, priming may occur in picture-picture pairs that results from the overlap in visual features common to the pictorial representations of objects from the same semantic category.     

Semantic access processing in a supra-modal deficit: a single case study

The case is presented of a semantic dementia patient, who shows a deficit selective for (i) conceptual class (living things), (ii) attribute processing (visual features) and affecting (iii) input-output modalities at the same processing stage (matching stored representation to attributes). The first experimental part aims at exploring the specific stage/process at which semantic knowledge breaks down through multi-modality tasks, devised to tap different levels within the semantic elaboration flow. The second focuses on the differences between category vs. attribute knowledge across various modalities. The core nature of the patient's deficit is investigated through a close comparison of her damage to a specific processing stage across modalities in the light of her class and attribute-specific impairment. The complex pattern of findings is discussed according to current theoretical accounts of semantic memory organization. Finally, the relevance of the adoption of a broad perspective when dealing with semantic memory impairments is highlighted.