Letter Search Research Articles

Semantic priming in the prime task effect: evidence of automatic semantic processing of distractors.

The automaticity of the semantic processing of words has been questioned because of the reduction of semantic priming when the prime word is processed nonsemantically--for example, in letter search (the prime task effect). In two experiments, prime distractor words produced semantic priming in a subsequent lexical decision task, but with the direction of priming (positive or negative) depending on the prime task. Lexico-semantic tasks produced negative semantic priming, whereas letter search produced positive semantic priming. These results are discussed in terms of task-based inhibition. We argue that, given the results from the distractors, the absence of semantic priming does not indicate an absence of semantic activation but reflects the action of control processes on prepotent responses when less practiced responses are needed.

On the interaction between linguistic and pictorial systems in the absence of semantic mediation: evidence from a priming paradigm.

Use of the letter search task in the context of the priming paradigm has proved to be an invaluable tool for the investigation of the strategic control of processes involved in word recognition. In particular, previous findings that letter search on a prime word interferes with the priming of semantically/associatively related targets, but not with the priming of either identical or morphologically related targets, suggests that letter search may selectively interfere with semantic processing, leaving other levels of processing intact. In the present experiments, this investigation was extended by exploring the priming of pictures following letter search of either a same-concept word (repetition priming) or a semantically/associatively related word (semantic priming). There was significant repetition priming of picture categorization following both silent reading and letter search of the prime word (Experiments 1 and 2). In contrast, semantic priming of pictures was found only following silent reading of the prime; there was no semantic priming following letter search of the prime (Experiment 2). This pattern of results suggests that focusing attention at the letter level during prime processing selectively attenuates activation of the semantic system by the prime. It does not prevent the spread of activation between the lexical and pictogen levels of representation of a given concept.

Word-based grouping affects the prime-task effect on semantic priming.

Semantic priming between words is reduced or eliminated if a low-level task such as letter search is performed on the prime word (the prime task effect), a finding used to question the automaticity of semantic processing of words. This idea is critically examined in 3 experiments with a new design that allows the search target to occur both inside and outside the prime word. The new design produces the prime task effect (Experiment 1) but shows semantic negative priming when the target letter occurs outside the prime word (Experiments 2 and 3). It is proposed that semantic activation and priming are dissociable and that inhibition and word-based grouping are responsible for reduction of semantic priming in the prime task effect.

Smoking after nicotine deprivation enhances cognitive performance and decreases tobacco craving in drug abusers

This study investigated the effects of nicotine deprivation and smoking on cognitive abilities and tobacco craving. Twenty smokers with histories of drug abuse completed the Questionnaire on Smoking Urges (QSU) and two cognitive tests before and after smoking two cigarettes during two 90-min sessions. After two cigarettes were smoked at Session 1, subjects were tobacco abstinent for 18 h until Session 2 the next morning. Response time on a logical reasoning test was unchanged by tobacco deprivation and was faster after smoking on Session 2. Deprivation slowed responding on a letter search test, which was reversed by smoking to pre-deprivation baseline. Tobacco deprivation increased scores on the QSU; smoking after deprivation reduced craving scores to smoking baseline levels. These results confirmed the utility of the QSU to measure changes in craving induced by tobacco deprivation and smoking. Further, the data suggest that deprivation-induced deficits and smoking-induced enhancements in performance may be specific to certain cognitive domains.

Levels of representation in visual word recognition: A dissociation between morphological and semantic processing.

A robust semantic priming effect typically occurs in visual word recognition if the prime is read before a response to the target. However, this effect is dramatically reduced if a letter search is performed on the prime prior to responding to the target. Three lexical decision experiments document the new observation that morphological priming is preserved following letter search on the prime. This dissociation between morphological and semantic priming following letter search can be understood in the context of an interactive activation framework. In addition, the implications of these results for connectionist and compound cue accounts of word recognition, as well as the issue of automaticity in word recognition, are discussed.

Visual Selective Attention and Reading Efficiency are Related in Children

We investigated the relationship between visual selective attention and linguistic performance. Subjects were classified in four categories according to their accuracy in a letter cancellation task involving selective attention. The task consisted in searching a target letter in a set of background letters and accuracy was measured as a function of set size. We found that children with the lowest performance in the cancellation task present a significantly slower reading rate and a higher number of reading visual errors than children with highest performance. Results also show that these groups of searchers present significant differences in a lexical search task whereas their performance did not differ in lexical decision and syllables control task. The relationship between letter search and reading, as well as the finding that poor readers-searchers perform poorly lexical search tasks also involving selective attention, suggest that the relationship between letter search and reading difficulty may reflect a deficit in a visual selective attention mechanisms which is involved in all these tasks. A deficit in visual attention can be linked to the problems that disabled readers present in the function of magnocellular stream which culminates in posterior parietal cortex, an area which plays an important role in guiding visual attention.

Word, Pseudoword, and Nonword Processing: A Multitask Comparison Using Event-Related Brain Potentials

Event-related brain potentials (ERPs) to words, pseudowords, and nonwords were recorded in three different tasks. A letter search task was used in Experiment 1. Performance was affected by whether the target letter occurred in a word, a pseudoword, or a random nonword. ERP results corroborated the behavioral results, showing small but reliable ERP differences between the three stimulus types. Words and pseudowords differed from nonwords at posterior sites, whereas words differed from pseudowords and nonwords at anterior sites. Since deciding whether the target letter was present or absent co-occurred with stimulus processing in Experiment 1, a delayed letter search task was used in Experiment 2. ERPs to words and pseudowords were similar and differed from ERPs to nonwords, suggesting a primary role of orthographic and phonological processing in the delayed letter search task. To increase semantic processing, a categorization task was used in Experiment 3. Early differences between ERPs to words and pseudowords at left posterior and anterior locations suggested a rapid activation of lexico-semantic information. These findings suggest that the use of ERPs in a multiple task design makes it possible to track the time course and the activation of multiple sources of linguistic information when processing words, pseudowords, and nonwords. The task-dependent nature of the effects suggests that the language system can use multiple sources of linguistic information in flexible and adaptive ways.

Phonology can help or hurt the perception of print.

Phonological manipulations affect performance in a letter search task that requires only a shallow level of processing. In Experiment 1, phonology reduced accuracy in the letter search task when a pseudohomophone (GAIM) contained a target letter ("i") that was missing in the spelling of its (nonpresented) sound-alike base word (GAME). In Experiment 2, phonology increased accuracy in the letter search task when the target letter was present in both the spelling of the pseudohomophone and the spelling of its sound-alike base word ("m" in GAIM and GAME). In Experiment 3, we showed that the phonology-hurts effect of Experiment 1 is not peculiar to nonword letter strings but generalizes to familiar words. In Experiment 4, we obtained a phonology-hurts effect on correct response times when stimuli were visible until participants responded (stimuli were not masked).

Phonology can help or hurt the perception of print.

Phonological manipulations affect performance in a letter search task that requires only a shallow level of processing. In Experiment 1, phonology reduced accuracy in the letter search task when a pseudohomophone (GAIM) contained a target letter ("i") that was missing in the spelling of its (nonpresented) sound-alike base word (GAME). In Experiment 2, phonology increased accuracy in the letter search task when the target letter was present in both the spelling of the pseudohomophone and the spelling of its sound-alike base word ("m" in GAIM and GAME). In Experiment 3, we showed that the phonology-hurts effect of Experiment 1 is not peculiar to nonword letter strings but generalizes to familiar words. In Experiment 4, we obtained a phonology-hurts effect on correct response times when stimuli were visible until participants responded (stimuli were not masked).

Semantic priming in visual word recognition: Activation blocking and domains of processing

The fact that letter search on a prime eliminates the typically robust semantic priming effect in lexical decision is often attributed to the "shallowness" of the prime-processing task. In three experiments we investigated this claim by using two different "shallow" prime-processing tasks: letter search and color identification. Consistent with previous reports, lexical decisions to semantically related targets were not facilitated when subjects searched the prime for a probe letter. In contrast, semantic priming was observed following a color discrimination task on the prime. We suggest that a levels-of-processing interpretation is not an adequate framework for understanding these data. Instead, a domain-specific processing account is offered in which explicit processing at the letter level (as in letter search) makes demands on resources (e.g., activation) that drives processing at the semantic level. This competition is resolved by establishing a temporary activation block at the lexical-semantic interface, which results in the elimination or attenuation of semantic priming. In contrast, global judgment of color is viewed as a domain that does not make demands on the resources that drive the visual word recognition machinery. There is therefore no need for an activation block, and semantic priming is not prevented.

Are visual search procedures adapted to the nature of the script?

Letters are processed differently from other shapes in a visual search task where subjects have to decide whether or not a predesignated target symbol is present in a subsequently presented string of five such symbols. If the M-shaped letter search function, which relates correct reaction time to target position, reflects an efficient strategy used in word recognition, it should be produced by skilled readers of English who also read a logographic script. A cross-linguistic study of biscriptal Mandarin/English and monoscriptal English readers (Expt 1) provided evidence of the generality of a basic search strategy for alphabetic targets. Hand-of-response affected the search function in an asymmetric fashion for both groups of readers, and although case differences between target and string increased reaction times overall, the classic M-shaped function remained. In Expt 2, we used a within-subjects design and examined the extent to which biscriptal Mandarin/English readers produced different search functions for letters and logographs. Consistent with expectation, these readers showed an M-shaped function for letters but a more U-shaped function for logographs. Hand-of-response exerted a consistent effect for both types of material. Taken together, these experiments support the view that skilled readers develop script-specific procedures.

When is a direct test of memory more sensitive than an indirect test?

Abstract A direct test of such as recognition is typically considered to be less sensitive than an indirect test such as lexical decision (e.g., Schacter, 1987). However in previous research we found that manipulations which eliminated of lexical decision did not eliminate of recognition In the present experiment we replicated and extended this result by including an additional indirect test - categorization. Subjects initially performed a lexical decision task, and were then given two tests for the words which had appeared in the lexical decision task: a direct recognition test and an indirect categorization test. In lexical decision, performing letter search on a prime eliminated of related targets. However, was preserved in recognition memory: Primes were better remembered if they had been followed by related as compared to unrelated targets during lexical decision. In contrast, categorization performance was unaffected by whether the lexical decision items had initially appeared in a related or an unrelated context. The dissociation suggests that different processes under - lie in lexical decision and in recognition The former is best explained in terms of spreading activation, whereas the latter is best explained in terms of integrative processing involved in the production of an episodic trace. Memory is studied by many people in many different ways. The different methods used by different investigators have, in large measure, led to the establishment of two quite distinct literatures. In one such literature the dependent measure is typically accuracy (as measured, for example, in the context of recognition memory, recall, and fragment completion). In another literature accuracy is near ceiling, and the primary dependent measure is the time taken to make a decision (as measured, for example, in lexical decision and naming). A further complication is that the former literature is typically thought of as the study of memory while the latter literature is often conceptualized as the study of visual word recognition and rather than of It is not our purpose here to discuss why the study of memory has developed as it has; without doubt there are many reasons (functional autonomy of methods comes easily to mind as one). Instead, we set out to mine a potentially rich lode which consists of looking at both measures in the context of an experiment on reading and memory. In the experiment reported here there is a dissociation between a direct and an indirect test in which the direct test (recognition memory) is more sensitive to a manipulation of context than is the indirect test (lexical decision). In short, a manipulation which eliminates the typically robust effect in lexical decision leaves an effect of preserved in recognition These data are consistent with the view that an episodic form of which likely subserves comprehension processes in should be thought of as distinct from the activation in that likely drives lexical decisions. Semantic Priming in Lexical Decision In the semantic priming paradigm(f.1), subjects are asked to process a target word such as BUTTER following the prior processing of either a related word such as BREAD or an unrelated word such as KING (e.g., Meyer & Schvaneveldt, 1971). It is now well documented that target processing is faster or more accurate or both following a related prime in a variety of tasks including lexical decision, perceptual identification, naming, and category decision (see Neely, 1991, for a review). However, it has also consistently been demonstrated that whether or not the prior processing of a prime word facilitates the processing of a related target depends on how the prime is processed. …

Letter Search for interfering pathways for atomic squeezed states

Letter Search for interfering pathways for atomic squeezed states

Temporal Factors in Visual Perception: A Differential Approach

The tradition in sensory and perceptual psychology is not to pay much attention to individual differences but to focus almost exclusively on normative or generic processes. Nevertheless, consistent individual differences may exist in sensory and perceptual processes, just as they do in all other areas of human behavior where their existence has been investigated. A preliminary study was made of flicker fusion frequency, apparent movement, and three other perceptual tasks as differential measures. With one exception, Letter Search, all of the tests were psychophysical rather than cognitive. All had to do with time; that is, perceptual speed mattered in all of them. The analysis focused on reliability, in the sense of consistency from trial to trial. Four of the five tests showed good reliabilities in this sense, while the fifth was borderline. In one test, Bistable Stroboscopic Motion, the dependent measure, interstimulus interval, showed a consistent though shallow tendency to lengthen with practice. In the remaining four tests practice effects were largely confined to the first two administrations.

Selective impairment of spatial attention during visual search in Alzheimer's disease.

Spatial attention during visual search was examined in 14 persons with mild Alzheimer's disease (AD) and 28 healthy older subjects, 14 aged 65-74 (young-old), and 14 aged 75-85 (old-old). Subjects searched for single feature (color) or conjunction (color + letter) targets in displays of 10 or 15 letters. Precues of differing sizes were used to provide localizing information of varying precision. Effects of display size and cue size on reaction time (RT) for color search were similar in AD subjects and controls. For color + letter search, however, AD patients showed minimal effects of cue size, pointing to an impairment in AD in the spatial focusing of attention during visual search. Pathology affecting the association parietal and extrastriate areas may mediate impairment of spatial attention and visual search in AD.

Vision Theory: Spatial and Temporal Factors

The psychometric properties of seven temporal factors (TFT) and five spatial factors (SFT) tests were assessed in a sample of 20 undergraduates. Subjects completed six repeated measures sessions of the TFTs and four trials of SFTs. All tests except Neisser's letter search produced stable measures. Reliabilities ranged from .81 to .98 for Simultaneity, Flicker, Search, and Bistable Stroboscopic Motion and from .59 to .71 for Masking, Phi, and Dynamic Visual Acuity. Of the 70 possible correlations between spatial and temporal batteries (7 TFTs X 5 SFTs X 2 distances), only four were significant. The moderate to high retest reliabilities, combined with the negligible correlations between spatial and temporal tests suggest that the two processes are largely independent.

Phonological Information Provides Early Sources of Constraint in the Processing of Letter Strings

Three experiments addressed the role of phonological information in visual word recognition using a letter search task. Subjects were presented with a target letter (e.g., "I") followed by a letter string (a word, a pseudohomophone, a pseudoword control, or a nonword). Their task was to indicate whether the target letter was present in the letter string. All experiments presented pseudohomophones (e.g., TAIP or BRANE) that either contained a letter (I) that was absent in their sound-alike word (TAPE) or were missing a letter (I) that was present in their sound-alike word (BRAIN). In Experiments 1 and 2, subjects made more miss errors under data-limited conditions when the letter string was a target-present pseudohomophone (TAIP) and more false alarm errors when the letter string was a target-absent pseudohomophone (BRANE). Experiment 2 controlled for a possible confound in the data in terms of word completion strategies. In Experiment 3, we replicated the pseudohomophone disadvantage using resource-limited conditions: detection times were longer for pseudohomophones. The existence of a pseudohomophone disadvantage in a supposedly graphemic task adds further support to the accumulating evidence that phonological information generated from the printed word is an early and major constraint in visual word recognition.

Capacity demands of automatic processes in semantic priming

In three experiments, we examined the effects of prime-target stimulus onset asynchrony (SOA) and the proportion of related primes and targets (relatedness proportion, or RP) on semantic priming when the prime was either named or was searched for a specific letter. In Experiment 1, with an RP of .50, priming occurred at SOAs of 240 and 840 msec when the prime was named, but no priming was found at either SOA when the prime was searched for a letter. In Experiment 2 the RP was either .20 or .80, and the SOA was set at 1,700 msec; priming again was found in both conditions when the prime was named, but only in the RP .80 condition when a letter search task was performed on the prime. In Experiment 3, both the proportion of related trials and SOA were varied; as in the previous experiments, no priming effects were found with the letter search task for either SOA in the RP .20 condition, but the priming effect was reinstated in the RP .80 condition. These results are discussed with respect to how limited capacity resources are allocated and how they influence semantic priming effects.

The effects of immediate stimulus repetition on reaction time and event-related potentials in tasks of different complexity.

The effect of immediate stimulus repetition was examined in lexical decision, face recognition, letter search, face/nonface discrimination, and word/number discrimination tasks using reaction time (RT), accuracy, and event-related brain potential (ERP) measures. Repetition facilitated performance in all tasks and for all stimulus types. However, ERPs were strongly affected by repetition only in lexical decision, face recognition, and letter search, when relatively long stimulus analysis and decision making processes were required. The ERP repetition effect consisted of a significant increase in P300 amplitude and a shortening of its latency. Repetition also resulted in the attenuation of a negative component that was tentatively identified as N400

Age and skill in visual search.

The effects of age and experience on visual-cognitive performance were examined by administering a domain-relevant visual search task and a standard letter search task to skilled and control subjects at 2 age levels (young and middle-aged adults). In the skilled task, subjects searched for a designated item within 3-item displays using images of bacteria morphology as targets and distractors. Each target was preceded by a word prime representative of bacteria morphology that was valid, invalid, or neutral with respect to the diagnostic characteristics of the target