Basic processes in reading: Computation of abstract letter identities.

A speeded classification experiment examined the hypothesis that an early processing stage in reading involves the computation of abstract letter identities. When 20 undergraduates were asked to base their classification on physical criteria, letter strings that differed in case but shared the same letter identities (e.g., HILE/hile) were classified as "different" less efficiently than strings with a common phonological code but different spelling (e.g., HILE/hyle). Letter strings with a common phonological code but different spelling were classified as efficiently as letter strings without a common phonological code (e.g., HILE/hule). Results of the present experiment, along with other experimental findings and some neuropsychological observations, provide converging evidence for a representation and comparison process that is neither visual nor phonological but is based on abstract letter identities. It is suggested that the computation of abstract letter identities is a precursor to lexical access during reading. Implications for the interpretation of certain developmental reading difficulties are noted. (French abstract) (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orthographic and lexical processing of visual letter strings.

Three experiments tested whether orthographic and lexical properties of a letter string influence the time to search for a component letter. 102 Canadian undergraduates served as Ss. Orthographic redundancy, defined by single-letter position-specific frequency, facilitated the search of targets specified prior to and simultaneously with the letter string. Words were searched faster than nonwords when the target followed the letter string. Neither orthographic nor lexicality had significant effects when the position of the target within the string was certain. Results are consistent with a hierarchical-levels model of word perception in which the activation of detectors at different levels is constrained by task demands. (French abstract) (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for sequential processing in visual word recognition.

The orthographic uniqueness point (OUP) of a word is introduced as the position of the 1st letter, reading from left to right, that distinguishes a word from all other printed words. In 3 experiments, observers named words that had early versus late OUPs. With unlimited viewing time, early-OUP words were named faster than late-OUP words. The effect disappeared in a delayed-naming task; hence, it was not associated with response production. The effect remained when exposure duration was reduced to limit eye movements. Results indicate that observers process the letters of a word in left-to-right order, contrary to strictly parallel accounts of word identification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Suedohomofoan effects in visual word recognition: Evidence for phonological processing.

Investigated the pseudohomophone effect, which is considered to be evidence that phonological recoding occurs in the lexical decision task in which a letter string like brane is identified as a nonword. 22 undergraduates read 156 letter strings, half of which were words, and identified them as words or nonwords. Half of the nonwords were pseudohomophones like brane, which sounds like a real word but is not spelled like one; half were strings like slint, which neither looks nor sounds like a real word. Response time to pseudohomophones was slower than response time to other nonwords. The interpretation of this result is that the letter string brane is transformed into a phonological code that accesses the entry for brain in a phonological lexicon, thus necessitating a time-consuming spelling check to avoid making a false positive response. Since letter strings like slint have no lexical entries, a postaccess spelling check is not necessary. Thus, the pseudohomophone effect reflects phonological processing. (French abstract) (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Types and tokens in visual letter perception.

Five experiments demonstrate that in briefly presented displays, subjects have difficulty distinguishing repeated instances of a letter or digit (multiple tokens of the same type). When subjects were asked to estimate the numerosity of a display, reports were lower for displays containing repeated letters, for example, DDDD, than for displays containing distinct letters, for example, NRVT. This homogeneity effect depends on the common visual form of adjacent letters. A distinct homogeneity effect, one that depends on the repetition of abstract letter identities, was also found: When subjects were asked to report the number of As and Es in a display, performance was poorer on displays containing two instances of a target letter, one appearing in uppercase and the other in lowercase, than on displays containing one of each target letter. This effect must be due to the repetition of identities, because visual form is not repeated in these mixed-case displays. Further experiments showed that this effect was not influenced by the context surrounding the target letters, and that it can be tied to limitations in attentional processing. (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)     

Sound affects the speed of visual processing.

The authors examined the effects of a task-irrelevant sound on visual processing. Participants were presented with revolving clocks at or around central fixation and reported the hand position of a target clock at the time an exogenous cue (1 clock turning red) or an endogenous cue (a line pointing toward 1 of the clocks) was presented. A spatially irrelevant sound presented 100 ms before the cue speeded visual latency when compared with a sound presented 100 ms after the cue. The effect of the sound was larger the farther the target was from fixation, and it was larger for endogenous than exogenous cues. A visual temporal warning signal had different effects on perceptual latency. These results demonstrate that an asynchronous sound can shift the perceived time of occurrence of a visual cue (temporal ventriloquism) and speed the velocity of the attentional shift toward the target. Sounds thus have multiple effects on visual perception. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Capacity limitations in visual word processing.

The ability of subjects to process English words in a spatially parallel manner was examined in several redundant-target detection tasks. When redundant targets were identical in a given display, processing limitations were evident in a task that required subjects to make semantic categorizations of words. However, parallel processing of identical redundant target words was exhibited in a lexical decision task that required a structural analysis of letter strings, but not an analysis of word meaning. The difference in performance in the two tasks suggests that the capacity for semantic processing is limited. Analyses designed to examine whether the redundancy gain in Experiment 2 could be attributed to limited capacity processing in conjunction with positional preferences provided evidence against this possibility. In addition, these analyses suggested that the processing times for the redundant targets in Experiment 2 might be positively correlated. In the third and fourth experiments, the redundant-target displays contained two different words. Processing interference, in the form of a redundancy loss, was evident in the lexical decision task, but not in the semantic categorization task, confirming a difference in the mode of processing between the two tasks. The results provide evidence against the unlimited-capacity, parallel processing hypothesis of late selection theories of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Familiarity effects in visual information processing.

Reviews the literature and deals, predominantly, with the issue of whether familiarity aids in the extraction of visual features or in the interpretation, either verbal or visual, of the features extracted. Familiar visual objects, such as normal letters and real words, are processed faster and more accurately than are unfamiliar objects. This fact is massively documented by a wide variety of studies, involving tachistoscopic recognition, visual comparison, and letter detection. Less clear is how and where familiarity has its effect. There actually appear to be several familiarity effects, some aiding the extraction and/or interpretation of visual information, others aiding nonperceptual processes (e.g., storing and reporting or comparing the information). (31/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Location confusions in visual information processing.

Tested in 2 experiments, using 21 undergraduates, the location-confusion model proposed by P. Dixon (see record 1986-21077-001) to account for interference that occurs when deciding whether a briefly presented target item appeared in a briefly presented array. The model assumed that information about the location of items decayed quickly and that Ss sometimes had difficulty deciding whether a particular identity code corresponded to the target or the array. Exp 1 confirmed the assumption that the interference only occurred with visual targets. Exp 2 tested for interference at the level of identity codes for well-learned vs arbitrary visual patterns (AVPs). No interference from AVPs on accuracy was observed. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parrel processing in visual short-term memory.

Visual short-term memory for the contrast and spatial frequency of sinusoidal gratings was measured in a delayed discrimination task in which the 2 stimuli to be compared were separated in time by 1-10 s interstimulus intervals (ISIs). Delayed discrimination thresholds for spatial frequency and contrast were compared, both when the 2 types of thresholds were measured in separate blocks of trials and when the 2 types of measures were randomly intermixed in an uncertainty paradigm, which required participants to process information about both dimensions on each trial. In both cases, accuracy of memory for spatial frequency was independent of ISI, but memory for contrast decreased as ISI increased. Performance was lower in the uncertainty case, but only by an amount predicted by statistical decision theory for independent sources. The results are consistent with a model assuming a set of parallel special-purpose visual discrimination and short-term memory mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The temporal dynamics of visual search: Evidence for parallel processing in feature and conjunction searches.

Feature and conjunction searches have been argued to delineate parallel and serial operations in visual processing. The authors evaluated this claim by examining the temporal dynamics of the detection of features and conjunctions. The 1st experiment used a reaction time (RT) task to replicate standard mean RT patterns and to examine the shapes of the RT distributions. The 2nd experiment used the response-signal speed-accuracy trade-off (SAT) procedure to measure discrimination (asymptotic detection accuracy) and detection speed (processing dynamics). Set size affected discrimination in both feature and conjunction searches but affected detection speed only in the latter. Fits of models to the SAT data that included a serial component overpredicted the magnitude of the observed dynamics differences. The authors concluded that both features and conjunctions are detected in parallel. Implications for the role of attention in visual processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional demands of processing shape in three-dimensional space: Evidence from visual search and precuing paradigms.

The hypothesis that representation of projective shape is preattentive whereas representation of objective shape in 3-dimensional space requires allocation of attention was tested in 2 visual search and 2 precuing experiments. In the visual search experiments, the slope for projective shape search was expected to approach 0 and that for objective shape search was expected to be a positive monotonic function of set size. In the precuing experiments, the effects of precuing were expected to be largely limited to the task requiring representation of objective shape. The overall pattern of results conformed to expectations. The findings are interpreted in the context of a model of shape-at-a-slant processing set out by W. Epstein and B. Lovitts (1985) and Epstein and T. Babler (1989, 1990). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size in the visual processing of faces and words.

Three experiments, with 34 right-handed university students, studied the influence of variations of stimulus size upon recognition of words and faces. Ss viewed a series of 640 slides of words of faces presented in 1 of 5 sizes and responded as to whether or not stimulus had been previously presented. Size played an important role in the recognition of faces but was irrelevant to the recognition of words. Analysis revealed that although irrelevant to recognition, size of words was nevertheless encoded, with some consequences similar to those for recognition of faces. The likelihood of recognition declined linearly with the numbers of words intervening between a word and its recurrence, while the likelihood of recognizing a face declined exponentially in the same circumstances. Results are interpreted in terms of stimulus-specific analyses, and this view is contrasted with other notions of mental representation. Variant measures are appended. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of short-term memory codes on visual image processing: Evidence from image transformation tasks.

Three experiments showed that phonological recoding of visual stimuli in short-term memory affects coding in long-term memory (LTM) and therefore performance on tasks involving generation and manipulation of visual images of the stimuli. An image transformation task was devised. It consists of mentally subtracting a part of an image to discover in the remainder another object. In Exp 1, Ss were required to learn a set of easily nameable visual stimuli and then perform the subtraction task on images retrieved from LTM. Performance was significantly better when initial learning was accompanied by articulatory suppression (AS). Exp 2 confirmed that AS had no effect when the task was performed on an image of a just-presented stimulus. In Exp 3, the nameability of the stimuli was manipulated. The results replicated the effect of AS for items that were easy to name but showed no effect of AS for stimuli that were difficult to name. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence of visual processing negativity with attention to orientation and color in central space

The aim of this study was to determine whether the visual frontal processing negativity reported in our earlier paper (Karayanidis, F. and Michie, P.T. Electroenceph. clin. Neurophysiol., 1996, 99: 38-56) is related to selection of spatial location, or occurs regardless of the stimulus features used to define the target. Subjects were instructed to respond to infrequent target stimuli of a particular combination of orientation, color and size. All stimuli were presented at central fixation. Posteriorly, orientation selection enhanced P125 amplitude over the right hemisphere but neither orientation nor color selection had an effect on N190. Posterior selection negativities emerged for orientation, color and their conjunction. At anterior sites, widespread effects of orientation and color processing were evident. The effect of location selection on the anterior N1 seen in our previous study was not evident with orientation selection. Instead, selection of orientation, color and their conjunction resulted in P145-250 frontally. Two later anterior negativities emerged. The early negativity (vPNe) was affected independently by orientation and color selection while the late negativity (vPNl) was affected only by selection of feature conjunction. Thus, the present results show that, like its auditory counterpart, the visual processing negativity occurs with a variety of stimulus classification features and is not exclusively related to spatial selection.     

Age and the selectivity of visual information processing.

Two experiments assessed age differences in the selectivity of visual information processing. Selectivity was measured by the amount of interference caused by nontarget letters when Ss detected a target letter in a visual display. In both experiments, young and elderly groups participated in search and nonsearch conditions; in the search condition, targets appeared anywhere in the display, whereas in the nonsearch condition targets were confined to the center position of the display. In Exp I, 20 19–27 yr olds and 20 65–90 yr olds were assigned to either condition for 2 sessions of testing. In Exp II, 16 young (mean age 19.8 yrs) and 16 elderly (mean age 71.8 yrs) Ss participated in both conditions. In both experiments, nontargets produced larger interference effects for old compared to young Ss in the search condition but not in the nonsearch condition. The obtained pattern of age effects could not be explained by age-related reductions in parafoveal acuity. Findings indicate that the magnitude of divided-attention deficit increases with age, whereas focused-attention deficits are unaffected by aging. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic processing of non-attended visual information.

In 2 experiments, with 28 university students, reaction time (RT) to name 1 of 2 rows of letter material was measured. The reported row was always a word. In Exp I, the nonreported row contained either a word semantically related to the reported word, a nonassociated word, or a nonword. Nonwords were not used in Exp II. Attentional selectivity was varied by presenting a report cue either 250 msec prior to display onset or 250 msec after display onset. RT was faster when the report cue preceded the display, indicating that this cue induced selective attention. In both the selective and nonselective conditions, RT to name the target word was faster when the nonreported row contained a word associated with the target than when it contained a nonassociated word. However, this facilitation of RT produced by associated nonreported words was greater under the nonselective condition. While semantic information was extracted from both nonattended and attended visual material a larger semantic interaction occurred when attention was directed to both rows of a visual display. Results also indicate that the presence of nonwords influenced the strategy used to analyze a visual display. (French summary) (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

From graphemes to abstract letter shapes: levels of representation in written spelling

The letter substitution errors of 2 dysgraphic subjects who, despite relatively intact oral spelling, made well-formed letter substitution errors in written spelling, were studied. Many of these errors bear a general physical similarity to the intended target. Analyses revealed that this similarity apparently was based on the features of the component strokes of letters rather than on visuospatial characteristics. A comparison of these subjects' letter substitution errors with those of 2 other individuals with brain damage, whose damage was at a different level of processing, revealed that the latter subjects' errors are not explicable in terms of stroke-feature similarity. Strong support was found for the computation of multiple representational types in the course of written spelling. This system includes a relatively abstract, effector-independent representational level that specifies the features of the component strokes of letters.