Irrelevant Letters Research Articles

Reading Direction and Attention - Effects on Lateralized Ignoring

The effects of the scan for the first element in reading (leftmost in English, rightmost in Hebrew) on the ability of subjects to ignore irrelevant stimuli in one visual field more than in the other were investigated. The hypothesis tested was that English readers would have a harder time ignoring irrelevant stimuli in the left visual held than in the right Visual field, with the opposite pattern predicted for readers of Hebrew. The paradigm employed by Banich (Banich & Belger, 1990) was used with two letter matching tasks. The results showed that when an irrelevant letter was present, English readers responded more slowly in the right than in the left visual field, and Hebrew readers showed the opposite pattern (Experiment 1). This interaction did not occur when the irrelevant letter was deleted (Experiment 2). These findings are discussed in terms of their relation to eye movements and covert attention and to the use of bilateral displays in neuropsychological experiments.

When global information and local information collide: a brain potential analysis of the locus of interference effects

The objective of the current experiment was to perform a psychophysiological investigation of the interference effects of global information on the analysis of local information, and vice versa. Subjects' choice reactions to letters at one level of information in a compound letter stimulus were impaired when letters at the other (irrelevant) level signified the opposite response. In the absence of differences in processing speed, global and local information produced symmetrical interference effects. Interference effects did vary, however, as a function of temporal advantage for the processing of information from either level. The individually faster level (be it global or local) interfered with the slower level but was itself relatively immune to such interference by the slower level. Analysis of event-related brain potentials and of the electromyogram revealed that incongruent irrelevant letters induced perceptual conflict but not response competition, thus pointing to a perceptual locus of processing dominance for the faster processed level of information in the compound stimulus.

Attentional distribution in the visual field during same-different judgments as assessed by response competition.

Judgments of same and different on a comparison task have been found to be subject to response competition if an irrelevant stimulus is presented in the display along with the target stimuli. For example, the reaction time for judging two letters the same is markedly increased if a different but irrelevant letter is also present in the display (C. W. Eriksen, O'Hara, & B. [A.] Eriksen, 1982). We have made use of this competition effect to map the visual attentional field in two dimensions. In two experiments, we varied the size of the attended area by varying the separation of the comparison stimuli. The boundaries of the attended area were mapped by varying the location of a response-competitive irrelevant noise letter. On this task, the attended area was found to be elliptical in shape, with the location of the target stimuli defining the major axis. The minor axis of the ellipse increased in direct proportion to increases in the major axis. Rather than interpret these field effects in terms of areas of enhanced processing, we propose that instead they represent the limits or failures in inhibition of competing stimulation.

Persistence of negative priming: Steady state or decay?

Responses to recently ignored stimuli may be slower and less accurate than responses to new stimuli. Neill and Westberry (1987) found that such negative priming effects dissipated within a 2-s interval between response and the next stimulus, the response-stimulus interval (RSI). However, experiments by Tipper, Weaver, Cameron, Brehaut, and Bastedo (1991) found negative priming persisted unchanged over RSIs from 1,350 to 6,600 ms. Our experiments used a letter-matching procedure in which target letters were flanked by irrelevant letters. Negative priming was manifested by longer reaction times and more errors to letters that had appeared as flankers in the preceding trial. RSI was varied from 500 to 8,000 ms.

Response-compatibility effects in focused-attention tasks: a same-hand advantage in response activation.

Previous studies have shown that responses can be partially activated by irrelevant stimuli in focused-attention tasks. In two experiments, such response activation was used to investigate the organization of keypress responses. Stimuli were rows of three letters, with a relevant target letter in the middle of the row and irrelevant flanker letters on the outside. There were four target letters, and these were assigned to four keypress responses made with the index and middle fingers of the two hands. Irrelevant flankers were parentheses, a neutral letter, or one of the four target letters. Responses were fastest when flankers were identical to the target, indicating facilitation of a response activated by both relevant and irrelevant letters. When flankers were response-incompatible target letters, responses were faster if these were target letters assigned to a response finger on the same hand as the correct response than if they were target letters assigned to a response finger on the opposite hand. The latter result is consistent with the hypothesis that simultaneous activation of two response fingers on the same hand produces faster responses than simultaneous activation of two response fingers on different hands, as assumed by Miller (1982). In Experiment 2, flankers were presented slightly before targets, and flankers that were same-hand target letters sometimes facilitated responses relative to the neutral parentheses flankers.

Absence of a redundant-signals effect in a reaction time task with divided attention.

In letter-identification reaction time experiments, a redundant-signals advantage was obtained when one location contained an irrelevant letter on single-target trials. It was not obtained when the position was blank. This confirms a prediction from a previous analysis in terms of variable criterion theory. The intercept of the linear function relating the growth of excitatory strength for redundant targets to that for the sum of single-target strengths is determined by the presence or absence of an irrelevant distractor. This confirms a second prediction. In this task, the redundant-signals advantage is due to distraction from an irrelevant stimulus occupying a relevant location. There is also evidence for a smaller distraction effect even from a redundant target. These findings are inconsistent with predictions of separate activation theory. Apparent differences be-tween these results and those of tachistoscopic recognition experiments are discussed.

Effects of sequence and variety of irrelevant items on visual search.

An experiment was done to determine how the sequence and variety of irrelevant items affects the speed of visual search. Three subjects searched for a target letter in sequences of predominantly alternating or repeating letters. Search through repeating sequences was faster than search through alternating sequences. Increasing the variety of irrelevant letters slowed search through alternating but not repeating sequences. Implications regarding eye fixations during visual search are discussed.

Decision times for word and letter search: A wholistic word identification model examined

Three experiments were carried out employing a reaction time paradigm developed by Johnson. Letter comparison time was found to increase when other irrelevant letters were present regardless of whether or not the letters made up a word or a word-like configuration. In addition word comparison time was found to increase when distractors were similar to targets. These findings were compared with other reaction time studies of word and letter identification, which together suggested that a hypothesis that words are analysed as single patterns may not be necessary to account for Johnson's data.

Is construction reserved for the target during visual search?

This study was designed to examine the possibility, that where there is high similarity between irrelevant and target letters, the irrelevant letter will be constructed to sudents each attended a 1-hr. experimental session in which they searched 25 lists, followed by a recognition test. The lists were made up from the upper case letters of the alphabet, and during the recognition test each S was required to indicate how many times each of the irrelevant letters had appeared on the final list searched. Analysis of variance showed a significant recognition frequency effect. The results indicated Neisser's (1967) view, that during visual search construction is reserved for the target, may require modification.

Some characteristics of selective attention in visual perception determined by vocal reaction time

Previous research had found that the accuracy with which an S could report an indicated letter or target in a briefly exposed multiletter display decreased as the number of irrelevant letters increased, and accuracy increased if the position of the target letter was indicated 150 msec before the display was presented. Iii the present experiment, these variables were reinvestigated using vocal reaction time as the dependent variable. An interpretation of the accuracy measures in terms of differential processing times was supported. The results of the two experiments were discussed in terms of a model of attentional selectivity.

Effects of noise similarity and redundancy on the information processed from brief visual displays

When a target letter form is presented tachistoscopicalfy and embedded in a matrix of irrelevant letter forms (noise), correct detections of the target at a given matrix size can be used to estimate indirectly the amount of information processed from the display, according to a model developed by Estes. In three experiments, the physical similarity between noise and target letters and noise-letter redundancy were varied to determine if the detection mechanism was responsive to these variables. It was found that increases in the physical differences between noise and target letters and increases in redundancy facilitated detection. It is argued that these data support a detection model that assumes parallel rather than serial information processing.

Erasure or partitioning in short-term memory

The possibility of erasure or partitioning in short-term memory was studied by instructing Ss to retrieve by free recall only 10 relevant letters embedded in a sequence of 20 visually presented letters. In the pre-cuing condition, irrelevant letters were indicated by a preceding blank, while in the post-cuing condition, irrelevant letters were indicated by a following blank. There was no difference in free recall under pre-cuing and post-cuing conditions, although free recall in both was better than chance. Free recall in a cueless control condition with irrelevant letters removed was better than in either pre- or post-cuing conditions. Analysis of errors suggests that irrelevant items were treated by partitioning or tagging in both cuing conditions, rather than by erasure, because cued-out letters occurred as errors of commission significantly more often than did letters which were not presented.