Repetition blindness: Levels of processing.

Repetition blindness (RB) is the failure to detect or recall repetitions of words in rapid serial visual presentation. Experiment 1 showed that synonym pairs are not susceptible to RB. In Experiments 2 and 3, RB was still found when one occurrence of the word was part of a compound noun phrase. In Experiment 4, homonyms produced RB if they were spelled identically (even if pronounced differently) but not if spelled differently and pronounced the same. Similarly spelled but otherwise unrelated word pairs appeared to generate RB (Experiment 5), but Experiment 6 produced an alternative account. Experiments 7 and 8 demonstrated that repeated letters are susceptible to RB only when displayed individually, not as part of two otherwise different words. It is concluded that RB can occur at either an orthographic (possibly morphemic) level or a case-independent letter level, depending on which unit (words or single letters) is the focus of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial repetition blindness for colour and shape.

The authors investigated three experiments on repetition blindness for briefly-presented masked displays containing only two coloured letters (one on either side of fixation). In Experiment 1, a single coloured letter (or nothing) was displayed on each side of fixation. Experiment 2 used a task in which subjects had to attend to Cl but not report it. They were either asked to report i) the colour of C2 if Cl was coloured, but the letter of C2 if Cl was white, or ii) the letter of C2 if Cl was a letter but the colour of c2 if cl was a nonletter symbol. RB was found for the features of the reported dimension, showing that attention to an item is sufficient to produce RB even if that item is not itself reported. And, in experiment 3, subjects reported either the colour of cl and the letter of C2 or vice versa, a task which required them to switch attended dimensions between Cl and C2. It is a question for future research whether RH simply requires prior attention to an object containing the repeated feature, or prior attention to the actual repeated feature itself. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Repetition blindness, forward and backward.

In these experiments, 2 letters were presented sequentially to the left and right of fixation, followed by pattern masks. Report was cued by spatial location (Experiments 1a, 1b, 2, 4, and 5) or temporal position (Experiments 3, 4, and 5). In all experiments, 2 identical letters on a trial resulted in reduced accuracy of report (repetition blindness; RB) for both the 1st and 2nd presented letters. This decrement was greater for the 2nd letter if subjects expected temporal cues, but tended to be greater for the Ist letter if they expected spatial cues. Analyses of errors and responses on catch trials indicated no bias against report of repetitions, and the repetition decrement did not interact with output order. The data are inconsistent with both type-refractoriness and memory-retrieval accounts of RB. A modified version of N. G. Kanwisher's (1987) token-individuation theory is proposed to account for the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are individual or consecutive letters the unit affected by repetition blindness?

When 2 similar words (e.g., react reach) are briefly sequentially displayed, the 2nd word may be omitted from the report, a phenomenon known as repetition blindness (RB). Previous researchers have suggested that consecutive letters are the unit affected by RB. Six experiments provided new data on orthographic RB. Two letters at the beginning or end of words resulted in RB, as did alternating interior letters (tactile earthly) and 3 letters with different relative positions (arid bird). However, no RB was found with a single final letter (show view). Observed RB may reflect pattern completion because RB for pairs like throat theory was reduced when the nonrepeated letters (eory) were consistent with only a single word. The experiments point to a model of orthographic RB in which both individual letters and letter sequences of length 2 or more play a role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measuring and modeling the trajectory of visual spatial attention.

In a novel choice attention-gating paradigm, observers monitor a stream of 3x3 letter arrays until a tonal cue directs them to report 1 row. Analyses of the particular arrays from which reported letters are chosen and of the joint probabilities of reporting pairs of letters are used to derive a theory of attention dynamics. An attention window opens 0.15 s following a cue to attend to a location, remains open (minimally) 0.2 s, and admits information simultaneously from all the newly attended locations. The window dynamics are independent of the distance moved. The theory accounts for about 90% of the variance from the over 400 data points obtained from each of the observers in the 3 experiments reported here. With minor elaborations, it applies to all the principal paradigms used to study the dynamics of visual spatial attention. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Location-specific target expectancies in visual search.

Observers searched for local target letters in global letter configurations. Different targets appeared with different frequencies in the different locations of the configurations. Experiment 1 showed that in each location, the target that was presented there more frequently was detected faster. Experiment 2 indicated that this location-specific target probability effect was due to perceptual facilitation and that facilitation was not restricted to letters but could be generalized to nonletter stimuli. Experiments 3 and 4 showed that the location distribution of targets could be acquired for 2 global configurations concurrently and that facilitation referred to locations within the configurations, not to screen locations. The results indicate a general sensitivity of the visual system for the location of details in global configurations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Signal detection analyses of repetition blindness.

Three experiments used a signal detection model to demonstrate that repetition blindness (N. Kanwisher; see record 1988-34836-001) reflects a reduction in sensitivity (d°) for the detection of repeated compared with unrepeated visual targets. In Experiment 1, repetition blindness (RB) was found for rapid serial visual presentation (RSVP) letter sequences, whether the visual targets were specified by category membership (vowels) or as 1 of 2 prespecified letters (e.g., A or O). In Experiment 2, RB was found to a similar degree even when the 1st critical item was displayed for twice as long as the other list items, although overall performance was considerably improved. Experiment 3 found RB for displays containing just 2 simultaneously presented letters. These results support Kanwisher's (1987) account of RB as a genuine perceptual effect, and rule out alternative accounts of RB as the result of response bias, output interference, or guessing biases. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Perceiving spatially inseparable objects: Evidence for feature-based object selection not mediated by location.

In 4 experiments, stimulus elements were arranged into an LED-like array, and letters were defined within the array by feature similarity between the elements with respect to color and form. These stimuli allowed the display of a target and a distractor letter simultaneously at the same location. They were spatially inseparable but could be separated in feature space. Participants had to identify the letter on a prespecified feature dimension (color or form). As a result, the distractors produced specific compatibility effects. This showed that nontarget features could not be ignored at an early stage (i.e., that color and form were processed automatically and in parallel up to a high stage). The target was selected from the resulting objects according to the prespecified feature dimension. Results demonstrate that object selection is possible without selecting absolute spatial arrays. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Components of the location probability effect in visual search tasks.

In visual search tasks, targets are detected more rapidly when they appear in locations that commonly contain a target than when they appear in locations that rarely contain a target. Five experiments were conducted to investigate 2 specific properties of this location probability effect. In Exp I spatial location of a stimulus row was varied to determine whether high location probability facilitates target detection in a particular location in visual space or a particular relative position within the row. Both were facilitated to approximately the same extent. In Exp II an inducing target occurred with high probability in 1 of 4 display locations, and a test target occurred with equal probability in all 4 locations. Both targets were found more quickly in the high-probability location than in the other locations, but the advantage associated with targets in the high-probability location was larger for the inducing target than for the test target. In Exps III–V the correspondence between the components observed in Exps I and II was examined. The overall pattern of results was compatible with a model in which the location probability effect is produced partly by an attentional spotlight, which facilitates processing of any stimulus appearing in a particular location in visual space, and partly by a network of position-specific letter detectors, which facilitates detection of a particular letter in a particular relative position within a display. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Position-specific masking and the word-letter phenomenon: Reexamining the evidence from the Reicher-Wheeler paradigm.

When choosing which of 2 equally plausible "critical" letters (e.g., n or h) was present in a briefly presented backward-pattern-masked target (the Reicher-Wheeler task), people are more accurate with words (e.g., show) than isolated letters (h). Contemporary accounts argue that pattern masks induce this word-letter phenomenon (WLP) because critical letters in words are more resistant to replacement from masking letter fragments occupying the same serial positions. The authors tested this notion by directly examining the effect of position-specific masking on critical-letter report using backward-pattern masks that occupied only each critical-letter position. Under these conditions, no WLP was observed, even though all noncritical letters in words were unmasked. However, a strong WLP was obtained when masks occupied all possible serial positions, including those of noncritical letters. Further experiments indicated that these masking effects were not confounded by attentional factors. Implications for contemporary accounts of the WLP and the structure of the word recognition system are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Location dominance in attending to color and shape.

Investigated in 4 experiments whether Ss direct attention to stimulus location when attempting to attend to its color or shape. In the 1st 2 experiments, a given property (location, color, or shape) of a letter cue instructed Ss whether to report any letters from a subsequent display. Regardless of which property was relevant, Ss reported letters adjacent to the cue and not those similar to its color or shape. In the last 2 experiments, the varied location of a cue was irrelevant to the task, whereas its varied color instructed Ss to report a letter in a given location or of a given shape. Targets adjacent to the cue were reported faster than those remote from the cue. The results suggest that attempting to attend to any aspect of a stimulus entails directing attention to location. (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)     

Evidence against the computation of abstract letter identities in visual processing.

Conducted 2 studies conceptually similar to the study of D. Besner et al (see record 1985-05766-001) in which letter strings were reorganized into sets where the single letters that were different were phonologically similar (e.g., G vs C) or dissimilar (e.g., G vs K). Latencies for same–different decisions about mixed-case letter strings were faster when the different letters were phonologically dissimilar. Results suggested skilled readers access name codes of individual letters in making their speeded classifications. In the present studies with 16 undergraduates, phonological similarity was manipulated in either the 1st or 4th letter of a mixed-case 4-letter string. A similarity effect was found when the 1st letter was varied. Results are not consistent with the view that abstract letter identities are computed in the course of same–different decisions about simultaneously presented mixed-case displays. (French abstract) (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of process schizophrenics on tasks involving visual search.

Compared the response times of 32 process schizophrenics and 16 nonhospitalized matched controls on 3 visual search tasks. Exp I involved the location of a target letter within an array of different background letters. Other experiments required a same–different response. Exp II involved the identification of a single different letter set within the uniform context of a square display formed by up to 40 replicates of another letter. Exp III presented 2 3–6 letter clusters in a single horizontal line. The 2 clusters were identical or had 1 different letter. Word and nonword clusters were used. Paranoid and nonparanoid groups did not differ on any measure. Schizophrenic response times were about 1 sec longer, but measures of rate of increase in response time with number of letters displayed did not generally differ significantly between groups. Schizophrenics tended to make more errors. Experimental manipulations affected the response times and error rates of schizophrenics and controls alike, and to much the same degree. Results suggest that process schizophrenics are not abnormally slow when extracting information from visual displays, and they appear to perform operations and strategies similar to those of normals when doing so. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why is word recognition impaired by disorientation while the identification of single letters is not?

Past research has shown that speed of identifying single letters or digits is largely indifferent to orientation, whereas the recognition of single words or connected text is markedly disrupted by disorientation. In a series of four experiments, we attempted to reconcile these findings. The results suggest that disorientation does not impair the identification of the characters but disrupts the perception of their spatial arrangement. When spatial order information is critical for distinguishing between different stimuli, disorientation is disruptive because some rectification process is required to restore order information. Utilizing the similarity between the letter B and the number 13, we found strong effects of orientation when a stimulus was interpreted as the two-digit number 13 but not when interpreted as the single letter B. This, however, occurred only when the set of numbers to be classified included permutations of the same digits. Odd–even decisions on single-digit and two-digit numbers (Experiment 3) yielded strong effects of stimulus orientation for order-dependent numbers (e.g., 32), weaker effects for order-independent numbers (e.g., 24), and none for repeated-digit (e.g., 22) or single-digit numbers. Classification time for two-letter Hebrew words evidenced strong effects of orientation for words that differed only in letter order but much weaker effects for words that had no letters in common, even when these were embedded within some words that did (Experiment 4). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why do infants make A not B errors in a search task, yet show memory for the location of hidden objects in a nonsearch task?

In 4 experiments, infants aged 8 to 12 months were tested on A not B search tasks, and nonsearch A not B tasks following the violation-of-expectation paradigm. A 1-location task and 2 control tasks were also conducted. In the nonsearch tasks, a toy was hidden in A, moved to B, and retrieved after a delay from either A (impossible) or B (possible). Results showed significantly longer looking times at impossible events, indicating some memory for where the object was hidden and an expectation of where it should be found. This effect occurred at delays at which infants made the A not B error when searching, and at a longer delay of 15 s. The results showed clearly that infants have some memory for the object's location, even at delays at which they search at the incorrect location. Discussion centers on how these results are accounted for within explanations of the A not B error. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of foveal load and visual context on peripheral letter recognition

Peripheral letter recognition was examined by presenting subjects with a letter triad centered 7.16 degrees to the right of fixation. At the same time, a single letter was presented at the point of fixation that was either the same as one of the letters in the triad or different from any of the triad letters. On other trials, no letter was presented at the point of fixation. Results supported and extended previous foveal load research. The disruptive effect of foveal load does not depend solely on the presence or absence of a foveal stimulus. Recognition of the first letter in non-words was disrupted when a foveal letter was presented that was different from the peripheral letter. Recognition of the middle letter for both words and non-words was disrupted when a foveal letter was presented that was the same as the middle letter. A significant interaction between foveal letter and triad type was also found. No evidence was found to suggest that recognition of a peripheral letter is significantly better when that same letter is also present at the point of fixation.     

Development and initial validation of a new procedure for evaluating adequacy of effort given during neuropsychological testing: The letter memory test.

The authors report on results from a new procedure for evaluating adequacy of effort given during neuropsychological testing. The letter memory test (LMT) is a computer-administered, 45-item, forced-choice recognition task that uses consonant letters as stimuli and manipulates face difficulty level along 2 dimensions: number of letters to be remembered and number of choices amongst which the target stimulus must be identified. In 3 studies that included either analogue or known groups designs, the LMT discriminated poorly motivated from well-motivated groups at a moderately high level of accuracy, which was comparable to that of the Digit Memory Test and superior to that of the 21-item Test. The internal consistency reliability of the LMT was also high. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Probability effects on stimulus evaluation and response processes.

Investigated the effects of probability information on response preparation and stimulus evaluation. Eight Ss responded with 1 hand to the target letter H and with the other to the target letter S. The target letter was surrounded by noise letters that were either the same as or different from the target letter. In 2 conditions, the targets were preceded by a warning stimulus unrelated to the target letter. In 2 other conditions, a warning letter predicted that the same letter or the opposite letter would appear as the imperative stimulus with .80 probability. Correct reactions times (RTs) were faster and error rates were lower when imperative stimuli confirmed the predictions of the warning stimulus. Probability information affected (1) the preparation of motor responses during the foreperiod, (2) the development of expectancies for a particular target letter, and (3) a process sensitive to the identities of letter stimuli but not to their locations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative Learning Improves Visual Working Memory Performance.

The ability to remember visual stimuli over a short delay period is limited by the small capacity of visual working memory (VWM). Here the authors investigate the role of learning in enhancing VWM. Participants saw 2 spatial arrays separated by a 1-s interval. The 2 arrays were identical except for 1 location. Participants had to detect the difference. Unknown to the participants, some spatial arrays would repeat once every dozen trials or so for up to 32 repetitions. Spatial VWM performance increased significantly when the same location changed across display repetitions, but not at all when different locations changed from one display repetition to another. The authors suggest that a major role of learning in VWM is to mediate which information gets retained, rather than to directly increase VWM capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)