Repetition effect in visual recognition of letters

This study examined the influence of the repetitive presentation of a letter on the recognition of two letters. In two experiments(4), two letters, which were either identical or not, were presented successively for a short duration at different spatial locations, and the subjects were required to identify them. In Experiment 1, the presentation time of the first letter was varied, whereas that of the second letter was constant. The results revealed that a reduced performance in identifying a second letter was observed in the case that the first letter, which was identical to the second letter, could be identified correctly. Experiment 2 examined whether or not this reduction was due to the identity of the visual shape of two letters. The first letter was presented either in the usual vertical orientation or rotated orientation by 180 degrees and the second letter was constantly presented in the usual orientation. The results revealed that a reduced performance in identifying a repeated letter was observed, regardless of the orientation of the first letter. The findings from the two experiments suggested that the identity of the information in memory was a main cause of the interference effect by repetition.     

Modality-specific coding in matching letters

Auditory and visual similarity was manipulated in a same-different reaction-time task to investigate the use of modality-specific codes in same-different judgments for pairs of letters. Experiment 1 showed that letters presented simultaneously in the auditory and visual modalities were matched on the auditory dimension. In Experiment 2, the letters were presented sequentially, and the modality of the second letter was randomly varied. Subjects matched the pairs on the modality dimension of the second letter even though the modality could not be reliably predicted. In Experiment 3, subjects judged adjacent pairs of letters presented for 50 msec, and in one condition they also named the letters. Matches were made on visual codes in both conditions. In general, the results indicate that when subjects are instructed to determine if two letters are the same, the letters will be matched on a modality-specific code in a way that will minimize the information processing necessary to complete the match.     

Naming and locating simultaneously and sequentially presented letters

Two letters varying in level of confusability were presented either simultaneously for 75 msec or sequentially for 75 msec each in adjacent retinal locations. The retinal locus of presentation varied from trial to trial, and subjects both identified and located the presented letters. Identification accuracy was higher on nonconfusable than on confusable letter pairs in the simultaneous condition, but not in the sequential condition. This result is interpreted as support for the notion that inhibition between similar or identical features shared by confusable letters occurs only when letters are presented simultaneously. A relative position effect, with performance on the peripheral letter higher than on the central letter, was found for simultaneously and second sequentially presented letters, but not for first sequentially presented letters. This result is interpreted in terms of the assumption that feature perturbations, with foveal perturbations more likely than peripheral perturbations, affect simultaneously and secondpresented letters, but not first-presented letters. The pattern of results for relative location accuracy showed many of the same effects as identification performance. A model assuming location errors reflect feature transpositions is outlined and is able to account for the absolute and relative location results and the correlation between relative location and identification accuracy.     

Synesthetic colors are elicited by sound quality in Japanese synesthetes

Determinants of synesthetic color choice for Japanese phonetic characters were studied in six Japanese synesthetes. The study used Hiragana and Katakana characters, which represent the same set of syllables although their visual forms are dissimilar. From a palette of 138 colors, synesthetes selected a color corresponding to each character. Results revealed that synesthetic color choices for Hiragana characters and those for their Katakana counterparts were remarkably consistent, indicating that color selection depended on character-related sounds and not visual form. This Hiragana–Katakana invariance cannot be regarded as the same phenomenon as letter case invariance, usually reported for English grapheme-color synesthesia, because Hiragana and Katakana characters have different identities whereas upper and lower case letters have the same identity. This involvement of phonology suggests that cross-activation between an inducer (i.e., letter/character) brain region and that of the concurrent (i.e., color) area in grapheme-color synesthesia is mediated by higher order cortical processing areas.     

Identity without form: Abstract representations of letters

Subjects viewed single letters and orthographically regular pseudowords in a tachistoscope at threshold duration. The pseudowords were either all of one case (upper or lower) or they were of mixed case. Letter identity (“A”) and case judgments were required for one letter on each trial. It was found that letter identity was often reported correctly when case was reported incorrectly, even for letters whose upper- and lowercase forms are physically dissimilar (e.g., G-g). This “case effect” was stronger for letters in pseudowords than for letters presented alone. It held across different type fonts, and it occurred even when the upper-and lowercase letters were of different sizes (gEaT) and when the instructions to the subjects stressed the greater importance of case reports over identity reports. The results are consistent with the view that letter identification is an automatic process, the product of which is an abstract representation containing no information about physical form.     

Processing letters in words at different levels

Subjects indicated whether two letters, two words, or a letter and the first letter of a word were the same. Letter targets were matched more quickly than word targets when the stimuli were presented simultaneously. When the target and comparison stimuli were separated by a 3-sec interval, word targets were matched more quickly than a letter and a letter in a word. It was also shown that the physical similarity of the targets and comparison stimuli had a greater effect in the simultaneous matching conditions. These findings are consistent with a model of word processing in which letters are individually compared prior to word identification at a physical level of processing. At a higher level of processing, words may be encoded as a unit, and the identification of the letters within the word may require a decoding of the word unit.     

Identification and pronunciation effects in a verbal reaction time task for words,pseudowords, and letters

The question addressed in this investigation was whether faster reading and pronunciation of words than orthographically regular pseudowords is due to faster identification or to faster programming and execution of the motor response. In Experiment I, three different response conditions (naming, threechoice signaled responding, and one-choice signaled responding) were employed to separate the identification and articulation processes in a verbal reaction time task. It was found that, for all intents and purposes, single, isolated letters are processed as if they were very short words. Words are read and pronounced 72 msec faster than pseudowords. Words are also pronounced 30 msec faster than pseudowords even if the reader has longer than 1 sec to identify the stimulus (three-choice condition) or to both identify the stimulus and preprogram the response (one-choice condition). The data indicate that words are identified about 52 msec faster and articulated about 30 msec faster than pseudowords. Since the number of response alternatives (one or three) does not interact with stimulus type (letter, word, or pseudoword) in the signaled response control condition, the 30-msec difference is due to response execution and not to differential response programming. Response programming takes in the neighborhood of 236 msec. Experiment 2 investigated the effect of local orthographic context upon the identification of the first letter of a string of letters. No difference was found in identifying the initial letter of words and pseudowords, but the initial letter of these orthographically regular letter strings was identified and named 10 msec faster than the initial letter of orthographically anomalous strings of letters (anagrams). The data from the two experiments are supportive of theories of reading that assume (1) that the letters of visually presented words are processed simultaneously, in parallel, (2) that there is a relatively direct access and retrieval of the phonological memory codes for the names of words, and (3) that orthographically regular pseudowords having no representation in the phonological lexicon undergo a grapheme-to-phoneme transformation that takes longer to finish than the direct spelling-to-sound process used for words.     

Phonological Assimilation and Visual Word Recognition

Are the visual word-processing tasks of naming and lexical decision sensitive to systematic phonological properties that may or may not be specified in the spelling? Two experiments with Hangul, the alphabetic orthography of Korea, were directed at the effects of the phonological process of assimilation whereby one articulation changes to conform to a neighboring articulation. Disyllabic words were responded to more quickly when (a) the final letter of the first syllable and the initial letter of the second syllable specified phonemes that satisfied rather than violated consonant assimilation, and (b) the vowel letters specified harmonious as opposed to disharmonious vowel phonemes. Discussion addressed the possible mediation of assimilation effects by consistency differences and theories that predict broad phonological influences on visual word recognition.     

Temporal limits of selection and memory encoding: A comparison of whole versus partial report in rapid serial visual presentation

People often fail to recall the second of two visual targets presented within 500 ms in rapid serial visual presentation (RSVP). This effect is called the attentional blink. One explanation of the attentional blink is that processes involved in encoding the first target into memory are slow and capacity limited. Here, however, we show that the attentional blink should be ascribed to attentional selection, not consolidation of the first target. Rapid sequences of six letters were presented, and observers had to report either all the letters (whole-report condition) or a subset of the letters (partial-report condition). Selection in partial report was based on color (e.g., report the two red letters) or identity (i.e., report all letters from a particular letter onward). In both cases, recall of letters presented shortly after the first selected letter was impaired, whereas recall of the corresponding letters was relatively accurate with whole report.     

Visual vs. verbal stimulus set in a letter-classification task

In three experiments, subjects classified briefly presented letters as belonging to either the first or the second half of the alphabet. Prior to each target letter, the subjects were given either a verbally named letter (verbal set), a letter presented visually for 3 sec (visual set), or no prior alternative (control). The target was equally likely to be the same as the prior alternative (same trials) or from the opposite half of the alphabet (different trials). Classification accuracy was always greater for visual set than for the control condition. Verbal-set accuracy was no better than control accuracy when the verbal alternative immediately preceded the target but was equal to visual-set accuracy when the alternative preceded the target by 3 sec. In both set conditions, subjects tended to choose the same half of the alphabet as the prior alternative. It was concluded that type and timing of prior alternatives are important variables in accounting for enhanced classification accuracy.     

Intrusion and location errors in the naming of letters in words and non-words

Summary In two experiments subjects were asked to report the identity of a position-cued critical letter in a linear array of letters. The identification errors made were classified either as intrusion (i.e., a report of a letter not in the array), or as location (i.e., a report of a noncritical or context letter from the array), and the arrays used were either unpronounceable non-words or words. In the first experiment all stimuli were four letters long and were presented in two parts: a leading array in which the information from two quadrants of a vertical by horizontal division of each letter was presented, and, after intervals of 40 and 160 ms, a trailing array of the complementary letter parts. The cue for the critical letter appeared either 80 ms before the initiation of the leading array or 320 ms after. The results showed a word advantage in all conditions, and an analysis of mislocations as proportions of total errors did not show that they differed significantly for non-words and for words. In the second experiment the stimuli were eight letters long and they were presented intact, followed after 140 ms by a patterned mask. The critical letter was again pre- and post-cued, and arrays subtended either 1.6° or 5° of visual angle. The results again showed a general word advantage and no difference in the proportions of mislocations for non-words and words. The results of both studies failed to provide support for the notion that the non-words probably required more attention than the words, and since this differential-attention hypothesis questioned the equality of encoding assumption of the Interactive Activation model of word perception, its rejection supported the latter proposition. It was concluded, therefore, that the encoding of the strings of letters in these studies was independent of their linguistic properties.     

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.     

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.     

Graded effects of number of inserted letters in superset priming

Three masked priming experiments investigated the effects of target word length and number of inserted letters on superset priming, where irrelevant letters are added to targets to form prime stimuli (e.g., tanble-table). Effects of one, two, three, and four-letter insertions were measured relative to an unrelated prime condition, the identity prime condition, and a condition where the order of letters of the superset primes was reversed. Superset primes facilitated performance compared with unrelated primes and reversed primes, and the overall pattern showed a small cost of letter insertion that was independent of target word length and that increased linearly as a function of the number of inserted letters. A meta-analysis incorporating data from the present study and two other studies investigating superset priming, showed an average estimated processing cost of 11 ms per letter insertion. Models of letter position coding are examined in the light of this result.     

Recognition vs recall of visually vs acoustically confusable letter matrices

In an attempt to separate auditory and visual components in short-term memory, five subjects were exposed to letter matrices composed of six visually confusable letters, six acoustically confusable letters, or a mixture of the two, under two response conditions: recognition and recall. A 50-msec stimulus presentation was followed by a variable dark interval of 1, 250, 1,000, or 3,000 msec. In the recall condition, the interval was followed by a buzzer which signaled the subject to recall, in any order, as many letters as possible. In the recognition condition, the variable interval was followed by a second letter matrix which was either identical to the first matrix or differed from is by one letter. Subjects responded either "same" or "different." The results support the notion that the auditory component plays a major role in recall, whereas the visual component dominates in recognition.     

Processing sets of letters for order: Evidence from reaction time experiments

In two experiments, subjects were required to impose different levels of organization on randomly ordered letters. In a between-subject design, the subject was to identify the letter in the set coming first in the alphabet or to reorganize the set into an alphabetic sequence. In a within-subject design, presentation of the letters was followed by an instruction to carry out the identification or reorganization task or to recite the letters in left-to-right order. Reaction time varied systematically with level of required organization, size of the presented set, and position and spacing of the letter set in the alphabet. The results are discussed in terms of two simple models.     

Holistic and analytic processes in the comparison of letters

College students made “same-different” judgments about successively presented pairs of letters whose degree of difference, in terms of the number of line segments out of register, was systematically varied. Reaction time was found to decrease with increases in the degree of difference in “different” responses, as well as to depend on the number of line segments present in the second (probe) letter. “Same” responses were much faster than different responses and were unaffected by the number of segments in the probe letter. This pattern of results suggests analytic (component-by-component) processing of “different” letters and holistic processing of “same” letters. The results have important implications for studies of multi-letter comparisons, in which it is commonly assumed that letter comparisons are holistic in nature.     

The effects of length and transposed‐letter similarity in lexical decision: Evidence with beginning,intermediate, and adult readers

Do length and transposed‐letter effects reflect developmental changes on reading acquisition in a transparent orthography? Can computational models of visual word recognition accommodate these changes? To answer these questions, we carried out a masked priming lexical decision experiment with Spanish beginning, intermediate, and adult readers (N=36, 44, and 39; average age: 7, 11, and 22 years, respectively). Target words were either short or long (6.5 vs. 8.5 letters), and transposed‐letter primes were formed by the transposition of two letters (e.g. aminal–ANIMAL) or by the substitution of two letters (orthographic control: arisal–ANIMAL). Children showed a robust length effect (i.e. long words were read slower than short words) that vanished in adults. In addition, both children and young adults showed a transposed‐letter priming effect relative to the control condition. A robust transposed‐letter priming effect was also observed in non‐word reading, which strongly suggests that this effect occurs at an early prelexical level. Taken together, the results reveal that children evolve from a letter‐by‐letter reading to a direct lexical access and that the lexical decision task successfully captures the changing strategies used by beginning, intermediate, and adult readers. We examine the implications of these findings for the recent models of visual word recognition.     

Children read normal and reversed letters: A simple test of reading skill

Above- and below-average readers in grades 3, 5 and 7 named letters under two conditions. In one condition, letters were presented in normal orientation. In the other condition, letters were presented in left-right mirror image orientation. The ratio of (1) naming time on normal letters to (2) naming time on mirror image letters was calculated for each child. Good readers had lower ratios than poor readers. This was due primarily to the faster naming of normal letters by good readers. Good and poor readers named mirror image letters at similar speeds. Two possible explanations for the results are discussed. One explanation is that the skilled readers have a better memory for the normal orientation of the letter shapes. A second explanation is that skilled readers process more peripheral information, when naming, than their less skilled counterparts, but that this peripheral processing is curtailed when transformed text is presented.