Interference effect caused by repetition in visual recognition of letters: Examination of the orthographic difference between two same letters1

Abstract: The present study examined the effect of phonological identity between two letters on the visual recognition of the letters. Participants were required to identify the two same or different letters that were successively presented for a short duration. In order to manipulate the phonological identity of the two letters, the orthography of the Kana letters was varied. In half of the trials, the first and second letters were presented in Hiragana (the same‐orthography condition). In the other half, the first letter was presented in Katakana, and the second letter in Hiragana (the different‐orthography condition). The results revealed that the identification performance for the second letter was reduced in the same‐orthography condition when the two letters were the same, compared with when they were different. In contrast to this, in the different‐orthography condition, the identification performance of the second repeated letter was marginally superior to that of the nonrepeated letter. Considering the present findings together with those of the author's previous study (Kuwana, 2004), it is suggested that the interference effect caused by repetition could result from the reduction in the availability of visual pattern information stored in long‐term memory.     

Orientation unbound: Dissociation of identity and orientation under rapid serial visual presentation

Participants were shown rapid sequences of three letters, flanked by digits, each rotated 0 degree, 90 degrees, 180 degrees, or 270 degrees clockwise from upright. In Experiment 1, the participants tried to report the letter that matched the orientation of an arrow, presented either before (before task) or after (after task) the sequence. A third task (total task) required them to report all of the letters. Accuracy for individual letters was significantly better in the total task than in the before task, and better in the before task than in the after task, suggesting particular difficulty in binding orientation to identity. In Experiment 2, the participants were given letter probes and were asked to indicate the orientation of the probed letter. Although report was above chance, there were frequent illusory conjunctions. Since perception of orientation must depend on prior establishment of identity, our results suggest that orientation and identity may become unbound during processing and are held in parallel storage systems.     

Single-Letter Retrieval Cues for Anagram Solution

Anagram solution, as related to single-letter retrieval cues and first letter of the solution word (consonant or vowel), was examined. In Experiment 1, college-aged solvers were presented both types of 5-letter words and either the first letter of the solution word as a cue, or no cue. In Experiment 2, the effects of four types of retrieval cues (first, middle, or last letter or no cue) upon solving consonant-beginning words was examined. Finally, Experiment 3 examined the solution of both types of solution words as related to the preceding four types of retrieval cues. The results of all 3 experiments showed that a single letter can be an effective cue. For consonant-beginning words, the middle and last letters were as effective as the first letter. For vowel-beginning words, the first letter was more effective than either the middle or last letter. It was concluded that solvers select one letter of the anagram, typically a consonant, to serve as the first letter of the solution word, and then rearrange the remaining letters.     

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.     

Task- and location-switching effects on visual attention

In two experiments, we examined the effects of task and location switching on the accuracy of reporting target characters in an attentional blink (AB) paradigm. Single-character streams were presented at a rate of 100 msec per character in Experiment 1, and successive pairs of characters on either side of fixation were presented in Experiment 2. On each trial, two targets appeared that were either white letters or black digits embedded in a stream of black letter distractors, and they were separated by between zero and five items in the stream (lags 1-6). Experiment 1 showed that report of the first target was least accurate if it immediately preceded the second target and if the two targets were either both letters or both digits (task repetition cost). Report of the second target was least accurate if one or two distractors intervened between the two targets (the U-shaped AB lag effect) and if one target was a letter and the other a digit (task switch cost). Experiment 2 added location uncertainty as a factor and showed similar effects as Experiment 1, with one exception. Lag 1 sparing (the preserved accuracy in reporting the second of two targets if the second immediately follows the first) was completely eliminated when the task required attention switching across locations. Two-way additive effects were found between task switching and location switching in the AB paradigm. These results suggests separate loci for their attentional effects. It is likely that the AB deficit is due mainly to central memory limitations, whereas location-switching costs occur at early visual levels. Task-switching costs occur at an intermediate visual level, since the present task switch involved encoding differences without changes in stimulus-response mapping rules (i.e., the task was character identification for both letters and digits).     

Transposed-letter effects in reading: evidence from eye movements and parafoveal preview

Three eye movement experiments were conducted to examine the role of letter identity and letter position during reading. Before fixating on a target word within each sentence, readers were provided with a parafoveal preview that differed in the amount of useful letter identity and letter position information it provided. In Experiments 1 and 2, previews fell into 1 of 5 conditions: (a) identical to the target word, (b) a transposition of 2 internal letters, (c) a substitution of 2 internal letters, (d) a transposition of the 2 final letters, or (e) a substitution of the 2 final letters. In Experiment 3, the authors used a further set of conditions to explore the importance of external letter positions. The findings extend previous work and demonstrate that transposed-letter effects exist in silent reading. These experiments also indicate that letter identity information can be extracted from the parafovea outside of absolute letter position from the first 5 letters of the word to the right of fixation. Finally, the results support the notion that exterior letters play important roles in visual word recognition.     

The role of attention in the shift from orientation-dependent to orientation-invariant identification of disoriented objects

In two experiments, the naming of rotated line drawings of natural objects was examined after a training phase in which the objects were either attended or ignored. In the training phase of Experiment 1, subjects were presented with objects in a number of orientations over five repeated blocks of trials. In the center of each object, seven letters (Xs and Ts, colored red or blue) were presented in rapid succession. Half the subjects named aloud the rotated object and ignored the changing letter display (object-attend). The other half ignored the object and counted the number of red Ts, and then used this number to perform a simple multiplication (object-ignore). In the test phase, all subjects named the rotated objects. The results showed that in the first block of trials in the training phase, mean naming time in the object-attend condition increased the further an object was rotated from the upright. This effect of orientation for attended objects was much reduced in the later presentations of the test phase. In contrast, there was no such benefit of prior presentation observed for the naming of objects that had previously been ignored. Instead, a substantial orientation effect was shown for the naming of previously ignored objects, which was similar to the orientation effect observed for attended objects named in the first block. Similar results were found in Experiment 2, in which object-attend subjects in training covertly named the objects and then performed a letter count and multiplication task. In both experiments, performance on the letter count and multiplication task varied with the angle of the ignored object. The results suggest that full attentional resources must be allocated in order for orientation-invariant representations to be formed and used in the identification of rotated objects.     

Memory for attended and unattended visual stimuli

Subjects were presented with lists of 'compound letters,' letters whose overall shapes were described by repeated use of replicates of other, smaller letters. In Experiment 1 subjects were asked to attend to either the overall letter or the smaller, constituent letter. At the end of list presentation, recall of all letters was required, but a postlist cue determined whether the attended or unattended letters were to be reported first. The results for four-item lists accorded with those of Martin (1978, 1980): order of report had a larger effect upon retention of attended letters than upon retention of unattended letters. The findings for three-item lists did not agree with Martin, however: first, the interaction of attention and order was weak; second, sharp recency for unattended letters was not found.

Experiment 2 required that subjects recall either in temporal pairs or by letter size. The results strongly suggest that the present paradigm does not constitute an analogue to dichotic listening. In particular, there is little evidence for a role for sensory retention of compound letters at time of recall.     

Global-local orientation congruency effects in visual search

In a visual search task, subjects had to decide which of 2 possible target letters was presented among 12 distractor letters. The 13 characters were arranged to form a global Navon-type letter. The global letter and the local letters (target and distractors) were independently presented in four different viewer-related orientations. When the global letter and the target were frequently congruently oriented, the response times increased with growing orientation disparity between them. This global-target congruency effect was independent from target identity (Experiment 1), and it diminished when global and target orientations were not correlated (Experiment 2). The results indicate that the orientation of the global letter can be deliberately used in order to facilitate the processing of congruently oriented local targets. The alignment of a spatial frame of reference is discussed as the most probable process underlying this facilitation.     

Interference in letter identification: A test of feature-specific inhibition

The role of perceptual interference in letter identification was investigated in three experiments designed to test the feature-specific inhibition model proposed by Bjork and Murray (1977). According to their extension of Estes’ (1972, 1974) interactive channels model, input channels leading to the same feature detector inhibit one another more than do channels leading to different detectors. The model therefore predicts perceptual interference between two letters to be a function of the degree of their feature overlap. Experiment 1 confirmed the feature-specific inhibition model and Bjork and Murray’s finding that the accuracy of report is lower when a briefly presented target letter is flanked by an identical letter than when flanked by another target letter or by a nontarget letter. Results from Experiment 2 indicated that single-target performance is a function of the degree of feature similarity between the target letter and background characters in a stimulus display. Experiment 3 ruled out a spatial-uncertainty explanation of feature-specific inhibition in a new paradigm that does not require subjects to process a poststimulus cue. The results of these experiments are discussed in relation to recent studies exhibiting strong effects of noise letters at the response stage of processing. It is suggested that discrepancies between feature-specific interference and response-interference studies may be a function of the particular mode of stimulus presentation and of the dependent measures that are used.     

Recognition of letters traced in the right and left palms: Evidence for a process-oriented tactile asymmetry

Three experiments were conducted to examine the relative ability of the cerebral hemispheres to identify capital letters traced in the palms of the hands. In Experiment 1, letters were presented either right side up or upside down, and the subject's task was to name the letter aloud or point to an identical letter using the stimulated hand. Analysis of the accuracy data revealed that the left palm/right hemisphere (LP/RH) performed this task significantly better than did the right palm/left hemisphere (RP/LH), particularly when the stimuli were presented in the upside-down orientation. In Experiments 2 and 3, subjects performed the same letter identification task; however, on half the trials, they were required to maintain either a spatial or verbal concurrent memory load (i.e., a 24-point Vanderplas & Garvin form or six low-imagery nouns, respectively). In the no-load condition of Experiment 2 (spatial forms), the previously observed LP/RH advantage was replicated. However, in the load condition, this LP/RH superiority was no longer in evidence. In Experiment 3 (low-imagery nouns), the presence of a concurrent verbal task had minimal impact on the previously observed performance asymmetry as the LP/RH advantage was obtained in both the no-load and load conditions. The results of the three studies taken in composite suggest that (1) the operations utilized to identify letters traced in the palms of the hands are primarily spatial in nature and (2) that the observed performance asymmetry may be attributed to a right hemisphere superiority for the analysis and codification of information along a spatial dimension. These findings are discussed in terms of a "process-oriented" model of hemispheric asymmetry.     

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.     

The role of item distinctiveness in short-term recall of order information

In two experiments, we examined short-term recall of order information using a partial-report distractor task. We manipulated the characteristics of a single letter in one of two four-letter segments. Participants knew in advance the identity of the letters in each segment. We made a single letter distinctive at presentation either by printing it in red or by replacing it with a red dash. Presenting the letter in red did not affect overall recall of the positions of the letters in the segment but did facilitate specific recall of the position of the distinct letter. Replacing the letter with a red dash inhibited overall recall as well as specific recall of the distinct letter. Participants were also less likely to respond in the regular output order when there was a dash replacing a letter in the segment. These effects of distinctiveness are explained in terms of output order processes in recent versions of the perturbation model.     

The meaning of the mask matters: evidence of conceptual interference in the attentional blink

The rapid serial visual presentation (RSVP) experiment reported here investigated the role of conceptual interference in the attentional blink (AB). Subjects were presented with RSVP streams that contained five stimuli: Target 1, a distractor, Target 2, a second distractor, and a symbol mask. Target 1 was a green letter, Target 2 was a red letter, and the distractors were either white letters or white digits. The stimuli were presented in a font typically seen on the face of a digital watch. Thus, "S" and "O" were identical to "5" and "0," respectively. This allowed us to present streams that were conceptually different even though featurally identical: The two letter targets were followed by distractors that were recognized either as "5" and "0" or as "S" and "O." The AB was substantially attenuated when subjects were told the distractors were digits rather than letters. This result indicates that conceptual interference plays a role in the AB.     

Priming and intrusion errors in RSVP streams with two response dimensions

Loach and Marí-Beffa (Vis Cogn, 10:513-526, 2003) observed that a distractor stimulus, presented immediately after a behaviorally relevant target stimulus, negatively primed a related probe stimulus indicating that the distractor had been inhibited. They argued that "post-target inhibition" may be a mechanism for preventing interference from temporally proximal stimuli; interference that could potentially result in a binding/intrusion error. In order to test this hypothesis, the authors carried out two rapid serial visual presentation (RSVP) experiments in which participants had to report either the identity (Experiment 1) or color (Experiment 2) of a target letter surrounded by distractor letters. In Experiment 1, a close relationship between priming and errors was observed. When a distractor stimulus showed evidence of being inhibited the participant was less likely to commit a binding error. The opposite was true when a distractor stimulus showed evidence of being facilitated. The results of Experiment 2 showed limited evidence of the same relationship.     

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.     

A response binding effect in visual short-term memory

The current study aimed to investigate the effect of action on the preservation of stored feature bindings. Prior research suggests that stimuli presented after a memory array can disrupt the feature bindings of memory array items. Here, we conducted three experiments to examine whether response to targets disrupts feature bindings. Two of four letters (A, B, C, D) were presented in a memory array, and were followed by a second array containing a single target letter. After either identifying or localizing the target letter, participants were required to report the identity or location of the memory array items. There was a deficit in memory performance involving spatial repetition when participants were required to localize targets, and involving identity repetition when participants were required to identify targets. We conclude that response codes are fundamentally linked to stimulus representations, and can affect retrieval from visual working memory.     

Which way is upright and normal? Haptic perception of letters above head level.

In three experiments, the perception of the apparent orientation of block letters shown in various orientations above the subject's head in the horizontal plane was examined. A block letter F with its front facing down toward the observer has two crossbars on its right side; the top is the part with the long crossbar, and the base has no bar. The experiments involved changing the locations of these parts with respect to the observer. In Experiment 1, the subjects using touch most often identified a letter as having its left and right sides in a normal orientation if the front of the block letter faced upwards away from the observer, with the bar on the right and the top of the letter farther from the subject than the letter's base. In Experiment 2, the subjects judging visual uprightness favored positions in which the bars were on the right, the top of the block letter was near them, and the letter's front faced downwards toward the observer. In Experiment 3, the subjects using touch most often assessed letters as being upright if the top of the letter was the farthest part and the bar was on the right. The results suggest that, when assessing orientation, subjects using touch favored positions that would be reached by a letter moving vertically upwards from table height, but subjects relying on vision favored positions reached by a letter moving in an are centered on the subject's head (on the eyes, in particular).     

Can “words” be processed as integrated units?

Three experiments examined the information processing of letters embedded within one-syllable words and similar unpronounceable sequences. A speeded discrimination task was used to detect processing differences between words and nonwords in a situation where both the identity and position of critical display information was known to subjects before stimulus presentation. Results indicated that word pairs differing by two letters were more quickly discriminated than two words differing in a single letter, while nonword pairs differing in two letters were discriminated no faster than two nonwords differing in a single letter. A further comparison showed a performance advantage for words over nonwords in a condensation task that forced a scan of stimulus letters for correct responding. These results suggest that familiarity affects information processing at a perceptual level, and are incompatible with theories suggesting that familiarity effects are due to inferential factors following letter feature analysis.     

Which way is upright and normal? Haptic perception of letters above head level

In three experiments, the perception of the apparent orientation of block letters shown in various orientations above the subject’s head in the horizontal plane was examined. A block letter F with its front facing down toward the observer has two crossbars on its right side; the top is the part with the long crossbar, and the base has no bar. The experiments involved changing the locations of these parts with respect to the observer. In Experiment 1, the subjects using touch most often identified a letter as having its left and right sides in a normal orientation if the front of the block letter faced upwards away from the observer, with the bar on the right and the top of the letter farther from the subject than the letter’s base. In Experiment 2, the subjects judging visualuprightness favored positions in which the bars were on the right, the top of the block letter was near them, and the letter’s front faced downwards toward the observer. In Experiment 3, the subjects using touch most often assessed letters as being upright if the top of the letter was the farthest part and the bar was on the right. The results suggest that, when assessing orientation, subjects using touch favored positions that would be reached by a letter moving vertically upwards from table height, but subjects relying on vision favored positions reached by a letter moving in an arc centered on the subject’s head (on the eyes, in particular).