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)     

Selective forward masking.

Assessed the effects of masking on recall accuracy in 2 experiments with a total of 28 male undergraduates. When a patterned masking stimulus was presented immediately before a centrally-fixated, tachistoscopically-presented 7-letter row (forward masking), a selective effect on recall accuracy was found, as measured by a partial-report technique. There was greater masking of the end letters than of the center letters in the displays. When the masking stimulus was presented immediately after the presentation of a letter row (backward masking), the results confirmed previous findings of greater masking of the center letters than the end letters. These different selective effects of forward and backward masking are consistent with the assumption that the processing of multiletter displays begins at the ends of the letter rows. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Position and order information in recognition memory.

In three experiments we examined short-term recognition memory for order information. In each, a target string of letters was followed by a test string to which the subject responded "same" or "different." The test string either was identical to the target, or it included a transposition of a single pair of letters. Results were consistent in showing that the closer two transposed letters were to another in the target string, the poorer was the recognition of transposition. A probed recall procedure introduced in Experiment 3 required subjects to identify the serial position in the target string held by the probe letter. This procedure showed that memory for a letter's serial position was distributed over a number of serial positions and that the overlap of such positional uncertainty functions for individual pairs of adjacent items predicted recognition memory for transposition. Uncertainty about position of occurrence appears to determine order information, at least in part, and constitutes a neglected aspect of current theories of serial-position phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frequency discrimination: Assessing global-level and element-level units in memory.

Assessed the retention of memory units for word-like strings of letters using the perceptions of 120 undergraduates in 2 experiments in determining how frequently various letters appeared. A series of strings was presented at 1 of 3 exposure durations. Within the series, the frequencies of occurrence of different strings and of the letters composing the strings were varied orthogonally. Results indicate that, at relatively long exposure durations, Ss could discriminate the frequency of occurrence for both strings and their constituent letters. The formation of global-level (string) memory units was indicated by judgments of string frequency being unaffected by either the frequencies of their component letters or experimental conditions (brief exposures) that prohibited accurate judgment of letter frequency. Although judgments of letter frequency were sometimes biased by the frequency of the strings containing the letters, the success with which the judgments discriminated different levels of letter frequency did not depend on the activation of string-level memory units. Furthermore, Ss' frequency judgments for letters were not predictable from their recall of the strings containing the letters. Results provide evidence for the formation of element-level (letter) memory units. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Location coding with letters versus unfamiliar, familiar, and labeled letter-like forms.

Errors in reporting a post cued target in a string of several letters more often involve a letter appearing elsewhere in the string (mislocation error) than one not appearing in the string (intrusion error). However, this difference is not found with strings of relatively unfamiliar symbols or forms. Two experiments, with a total of 70 Ss, explored the reason for this difference. Exp 1 showed that the difference was not an artifact of different overall accuracy levels or exposure durations for the 2 character types. In Exp 2, relative to no experience, initial experience with the forms through familiarization or learning labels for them produced mislocation and intrusion frequencies that were more similar to those for letters. This change was related to the development of stored representations for forms that are similar to those for letters. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Letter encoding in visual word identification: More evidence for a word-integration explanation for parafoveal preview effects in reading.

A letter string presented briefly in the parafovea facilitates naming a foveally presented word provided that the two stimuli are orthographically similar. The facilitation is asymmetrical in that to obtain it, both letter strings must have the first letters in common. One possible explanation, a letter-integration hypothesis, proposes that readers only identify the letters at the beginning of the parafoveal stimulus, an action that facilitates processing the target. Another explanation, a word-integration hypothesis, postulates that all the letters of the parafoveal stimulus are identified and that the asymmetry occurs because the first letters of the parafoveal stimulus are weighted more heavily than the later ones. The two accounts differ in the way the position of the first letter is determined. To distinguish the views, English and Hebrew stimuli were presented to 7 bilingual readers. 12 normal students participated as controls. Readers could not anticipate the position of the first letters; hence, if the letter-integration explanation is correct, the asymmetry in the priming should be attenuated. Consistent with the word-integration explanation, however, priming occurred when the target shared the beginning letters with the prime in both languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibition in verbal working memory revealed by brain activation

There are many occasions in which humans and other animals must inhibit the production of some behavior or inhibit the processing of some internal representation. Success in inhibitory processing under normal circumstances can be revealed by the fact that certain brain pathologies render inhibitory processing ineffective. These pathologies often have been associated with damage to frontal cortex, including lateral and inferior aspects. We provide behavioral evidence of a verbal working memory task that, by hypothesis, engaged inhibitory processing, and we show (by using positron emission tomograpny) that the inhibitory processing is associated with a lateral portion of the left prefrontal cortex. The task in which subjects engaged was item-recognition: Four target letters were presented for storage followed, after a brief interval, by a probe letter that could match a target letter or not. On some trials, when the probe did not match a target letter and therefore required a "no" response, the probe had matched a target letter of the previous trial, so on these trials a "yes" response was prepotent and had to be inhibited, by hypothesis. Compared with a condition in which no prepotent response was created, this condition yielded brain activation in left inferior frontal gyrus, in the region of Brodmann's area 45.     

On the selective effects of a patterned masking stimulus.

Investigated previous findings which suggest that a patterned masking stimulus, presented immediately following tachistoscopic presentation of letter rows, produces large decrements in the recall of letters from the central positions in the rows but has little effect on recall from either end of the displays. 4 experiments with 92 undergraduate Ss confirm the existence of a selective masking effect. The effect was obtained following exposure durations which varied from 30-200 msec. and with both full- and partial-report techniques. Also the selective masking effect was limited to multiletter displays in that it was shown that single letters were masked equally well across the positions used for an entire row. Results suggest that both ends of multiletter displays are processed and identified before the center positions of the displays are processed. (French summary) (15 ref.) (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)     

Font regularity constraints on the process of letter recognition.

Strings of four unrelated letters were presented for subjects to identify, followed by a patterned mask and then a forced choice test of each letter position. In Experiment 1, the type style in the regular conditions was consistent—all of the letters were of a single type font—whereas in the mixed condition, each string contained letters from two type fonts. Compared with the mixed condition, accuracy in the regular conditions was higher overall and increased at a faster rate as a function of processing time. This held across four sessions. In Experiment 2, the font in the mixed condition was varied either between or within letter strings; sizeable advantages for the regular conditions were found with both mix-methods. The results are consistent with the idea of a schemalike perceptual system that becomes tuned to the regularities of a particular font in order to process visual information efficiently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is the orthographic/phonological onset a single unit in reading aloud?

Two main theories of visual word recognition have been developed regarding the way orthographic units in printed words map onto phonological units in spoken words. One theory suggests that a string of single letters or letter clusters corresponds to a string of phonemes (Coltheart, 1978; Venezky, 1970), while the other suggests that a string of single letters or letter clusters corresponds to coarser phonological units, for example, onsets and rimes (Treiman & Chafetz, 1987). These theoretical assumptions were critical for the development of coding schemes in prominent computational models of word recognition and reading aloud. In a reading-aloud study, we tested whether the human reading system represents the orthographic/phonological onset of printed words and nonwords as single units or as separate letters/phonemes. Our results, which favored a letter and not an onset-coding scheme, were successfully simulated by the dual-route cascaded (DRC) model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001). A separate experiment was carried out to further adjudicate between 2 versions of the DRC model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Size scaling and spatial factors in visual attention

This study investigates the effect of the visibility of near and far letter distractors on target processing by scaling the size of the distractor letters to compensate for changes in resolution across the visual field. In Experiment 1, scaled and unscaled distractors were presented at varied stimulus onset asynchronies. Results showed that scaling the size of distractor letters in relation to their distance from the target was effective in producing strong compatibility effects. Scaled distractors presented prior to, or simultaneously with, the target were found to interfere with target processing whether they were near or far from the target. Experiment 2 used scaled distractors and varied the presentation location and the amount of time for processing prior to the presentation of the target. Compatibility effects were found to vary by location and by the exposure duration of the distractor. The finding of distance effects at far locations supports a space-based visual-attention mechanism with a wide attention beam (Steinman, Steinman, & Lehmkuhle, 1995).     

A theory of order relations in perceptual matching.

Relates order relations to research on retrieval processes and the representation of order information in memory. In 2 experimental tests, presentation of a study string of letters was followed by a test string to which the 6 undergraduate Ss responded "same" or "different." When adjacent letters were switched, RT was long and accuracy low, suggesting that a test letter is not simply compared to the letter in the same position in the study string; rather, the comparison is distributed across positions. The memory model assumes that the representation of a letter is distributed over position and that the comparison process assesses the amount of overlap between the test string and the memory representation. The diffusion retrieval model and overlap memory model are fitted to the data and goodness-of-fit is assessed. Shortcomings of alternative models are considered and applications of the model to related matching tasks, such as D. Taylor's (1976) converse of the perceptual matching task, and Angiolillo-Bent and L. Rips's (1981) multiple-element comparison task, are described. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Cd2+, Pb2+ and CH3Hg+ on high voltage-activated calcium currents in pheochromocytoma (PC12) cells: potency, reversibility, interactions with extracellular Ca2+ and mechanisms of block

The present study attempted to determine the relationship between affective disposition and the favorability of letters of reference. We hypothesized that individuals with positive dispositions would write more favorable letters than would individuals with less positive or neutral dispositions. In addition, we also hypothesized that length of letter would partly mediate the relationship between affective disposition and letter favorability. To test these hypotheses, two studies were conducted. In order to present letter writers with a controlled stimulus, Study 1 entailed having 110 undergraduate students write letters of reference for two hypothetical job candidates in a laboratory setting. In order to test the generalizability of the laboratory study, Study 2 involved 95 faculty members who submitted three recent letters of reference they had written. Results showed that affective disposition was related to the favorability of letters of reference in both studies. Results also revealed that length of letter partly mediated the relationship between affective disposition and letter favorability. Copyright 1998 Academic Press.     

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)     

Hierarchical control and skilled typing: Evidence for word-level control over the execution of individual keystrokes.

Routine actions are commonly assumed to be controlled by hierarchically organized processes and representations. In the domain of typing theories, word-level information is assumed to activate the constituent keystrokes required to type each letter in a word. We tested this assumption directly using a novel single-letter probe technique. Subjects were primed with a visual or auditory word or a visually presented random consonant string and then probed to type a single letter from the prime or another randomly selected letter. Relative to randomly selected letters, probe responses were speeded for first, middle, and last letters contained in visual and auditory word primes but not for middle and last letters contained in random consonant primes. This suggests that word-level information causes parallel activation of constituent keystrokes, consistent with hierarchical processing. The role of hierarchical processing in typing and routine action is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Turning selective attention failure into selective attention success.

In a letter identification task in which a centrally-presented letter is to be attended and laterally-flanking letters ignored, B. A. and C. W. Eriksen (1974) have shown effects on performance of the to-be-ignored letters when they contain information about the correct response. These data constitute important evidence of late selection for attention on condition that the flankers are not, in fact, attended. Three experiments with 168 undergraduates assessed the importance of task practice, positional uncertainty (PU) regarding the flankers, PU regarding the target, the proportion of flankers in a display that contain information about the response, and the strength of the target-response mapping. The effect of flankers on performance was independent of target PU and strength of target-response mapping, but varied with practice on the task, flanker-PU, and proportion of informative flankers. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relative position priming effect depends on whether letters are vowels or consonants.

The relative position priming effect is a type of subset priming in which target word recognition is facilitated as a consequence of priming the word with some of its letters, maintaining their relative position (e.g., csn as a prime for casino). Five experiments were conducted to test whether vowel-only and consonant-only subset primes contribute equally to this effect. Experiment 1 revealed that this subset priming effect emerged when primes were composed exclusively of consonants, compared with vowel-only primes (csn-casino vs. aia-animal). Experiment 2 tested the impact of letter frequency in this asymmetry. Subset priming effects were obtained for both high- and low-frequency consonants but not for vowels, which rules out a letter frequency explanation. Experiment 3 tested the role of phonology and its contribution to the priming effects observed, by decreasing the prime duration. The results showed virtually the same effects as in the previous experiments. Finally, Experiments 4 and 5 explored the influence of repeated letters in the primes on the magnitude of the priming effects obtained for consonant and vowel subset primes (iuo-dibujo and aea-madera vs. mgn-imagen and rtr-frutero). Again, the results confirmed the priming asymmetry. We propose that a functional distinction between consonants and vowels, mainly based on the lexical constraints imposed by each of these types of letters, might provide an explanation for the whole set of results. (PsycINFO Database Record (c) 2011 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)     

Comparison requirements and attention in identical-nonidentical stimulus discriminations.

Perceptual matching data show several puzzling effects. Particularly problematic are the disparities between the processing rates for same and different stimuli—the fast–same effect—and between the processing rates for two same–different judgment tasks that are related as mirror images—the task effect. Current models have difficulty accounting simultaneously for both effects. Central to these models is a stimulus comparison process that derives relative judgments of sameness and difference from tests of the congruence of stimulus representations. A contrasting view holds that same–different judgments can be modeled as absolute, rather than relative, judgments. This latter view is shown to be supported by experimental data. Reaction times (RTs) for judgments of identical letter strings increase with string length at the same rate whether judgments are based on all the information in the strings or just the information in a single pair of component letters. The data show that stimulus comparisons of the sort described by previous models are not involved in these judgments. An attentional model accounts for the data and for the fast–same and task effects as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)