The role of spatial attention in visual word processing

Which Factors Modulate Letter Position Coding in Pre-literate Children?

One of the central landmarks of learning to read is the emergence of orthographic processing (i.e., the encoding of letter identity and letter order): it constitutes the necessary link between the low-level stages of visual processing and the higher-level processing of words. Regarding the processing of letter position, many experiments have shown worse performance in various tasks for the transposed-letter pair judge-JUDGE than for the orthographic control jupte-JUDGE. Importantly, 4-y.o. pre-literate children also show letter transposition effects in a same-different task: TZ-ZT is more error-prone than TZ-PH. Here, we examined whether this effect with pre-literate children is related to the cognitive and linguistic skills required to learn to read. Specifically, we examined the relation of the transposed-letter in a same-different task with the scores of these children in phonological, alphabetic and metalinguistic awareness, linguistic skills, and basic cognitive processes. To that end, we used a standardized battery to assess the abilities related with early reading acquisition. Results showed that the size of the transposed-letter effect in pre-literate children was strongly associated with the sub-test on basic cognitive processes (i.e., memory and perception) but not with the other sub-tests. Importantly, identifying children who may need a pre-literacy intervention is crucial to minimize eventual reading difficulties. We discuss how this marker can be used as a tool to anticipate reading difficulties in beginning readers.

Letter and word identification in the fovea and parafovea

We investigated the extent to which accuracy in word identification in foveal and parafoveal vision is determined by variations in the visibility of the component letters of words. To do so we measured word identification accuracy in displays of three three-letter words, one on fixation and the others to the left and right of the central word. We also measured accuracy in identifying the component letters of these words when presented at the same location in a context of three three-letter nonword sequences. In the word identification block, accuracy was highest for central targets and significantly greater for words to the right compared with words to the left. In the letter identification block, we found an extended W-shaped function across all nine letters, with greatest accuracy for the three central letters and for the first and last letter in the complete sequence. Further analyses revealed significant correlations between average letter identification per nonword position and word identification at the corresponding position. We conclude that letters are processed in parallel across a sequence of three three-letter words, hence enabling parallel word identification when letter identification accuracy is high enough.

The closing of the theory of mind: A critique of perspective-taking

Theory of mind (ToM) is defined as the ability to attribute mental states to oneself and others and is often said to be one of the cornerstones of efficient social interaction. In recent years, a number of authors have suggested that one particular ToM process occurs spontaneously in that it is rapid and outside of conscious control. This work has argued that humans efficiently compute the visual perspective of other individuals. In this article, we present a critique of this notion both on empirical and theoretical grounds. We argue that the experiments and paradigms that purportedly demonstrate spontaneous perspective-taking have not as yet convincingly demonstrated the existence of such a phenomenon. We also suggest that it is not possible to represent the percept of another person, spontaneous or otherwise. Indeed, the perspective-taking field has suggested that humans can represent the visual experience of others. That is, going beyond assuming that we can represent another's viewpoint in anything other than symbolic form. In this sense, the field suffers from the same problem that afflicted the "pictorial" theory in the mental imagery debate. In the last section we present a number of experiments designed to provide a more thorough assessment of whether humans can indeed represent the visual experience of others.

The first letter position effect in visual word recognition: The role of spatial attention

A prominent question in visual word recognition is whether letters within a word are processed in parallel or in a left to right sequence. Although most contemporary models posit parallel processing, this notion seems at odds with well-established serial position effects in word identification that indicate preferential processing for the initial letter. The present study reports 4 experiments designed to further probe the locus of the first position processing advantage. The paradigm involved masked target words presented for short durations and required participants to subsequently select from 2 alternatives, 1 which was identical to the target and 1 that differed by a single letter. Experiment 1 manipulated the case between the target and the alternatives to ensure that previous evidence for a first position effect was not due to simple perceptual matching. The results continued to yield a robust first position advantage. Experiment 2 attempted to eliminate postperceptual decision processes as the explanatory mechanism by presenting single letters as targets and requiring participants to select an entire word that contained the target letter at different positions. Here the first position advantage was eliminated, suggesting postperceptual decision processes do not underlie the effect. The final 2 experiments presented masked stimuli either all vertically (Experiment 3) or randomly intermixed vertical and horizontal orientation (Experiment 4). In both cases, a robust first position advantage was still obtained. The authors consider alternative interpretations of this effect and suggest that these results are consistent with a rapid deployment of spatial attention to the beginning of a target string which occurs poststimulus onset. (PsycINFO Database Record

Lack of visual field asymmetries for spatial cueing in reading parafoveal Chinese characters

In two experiments, we investigated whether visual field (VF) asymmetries of spatial cueing are involved in reading parafoveal Chinese characters. These characters are different from linearly arranged alphabetic words in that they are logograms that are confined to a constant, square-shaped area and are composed of only a few radicals. We observed a cueing effect, but it did not vary with the VF in which the Chinese character was presented, regardless of whether the cue validity (the ratio of validly to invalidly cued targets) was 1:1 or 7:3. These results suggest that VF asymmetries of spatial cueing do not affect the reading of parafoveal Chinese characters, contrary to the reading of alphabetic words. The mechanisms of spatial attention in reading parafoveal English-like words and Chinese characters are discussed.

Automaticity revisited: when print doesn't activate semantics

It is widely accepted that the presentation of a printed word “automatically” triggers processing that ends with full semantic activation. This processing, among other characteristics, is held to occur without intention, and cannot be stopped. The results of the present experiment show that this account is problematic in the context of a variant of the Stroop paradigm. Subjects named the print color of words that were either neutral or semantically related to color. When the letters were all colored, all spatially cued, and the spaces between letters were filled with characters from the top of the keyboard (i.e., 4, #, 5, %, 6, and *), color naming yielded a semantically based Stroop effect and a semantically based negative priming effect. In contrast, the same items yielded neither a semantic Stroop effect nor a negative priming effect when a single target letter was uniquely colored and spatially cued. These findings (a) undermine the widespread view that lexical-semantic activation in word reading is automatic in the sense that it occurs without intention and cannot be derailed, and (b) strengthens the case that both implicit and explicit forms of visual word recognition require spatial attention as a necessary preliminary to lexical-semantic processing.

Spatial attention in written word perception

The role of attention in visual word recognition and reading aloud is a long debated issue. Studies of both developmental and acquired reading disorders provide growing evidence that spatial attention is critically involved in word reading, in particular for the phonological decoding of unfamiliar letter strings. However, studies on healthy participants have produced contrasting results. The aim of this study was to investigate how the allocation of spatial attention may influence the perception of letter strings in skilled readers. High frequency words (HFWs), low frequency words and pseudowords were briefly and parafoveally presented either in the left or the right visual field. Attentional allocation was modulated by the presentation of a spatial cue before the target string. Accuracy in reporting the target string was modulated by the spatial cue but this effect varied with the type of string. For unfamiliar strings, processing was facilitated when attention was focused on the string location and hindered when it was diverted from the target. This finding is consistent the assumptions of the CDP+ model of reading aloud, as well as with familiarity sensitivity models that argue for a flexible use of attention according with the specific requirements of the string. Moreover, we found that processing of HFWs was facilitated by an extra-large focus of attention. The latter result is consistent with the hypothesis that a broad distribution of attention is the default mode during reading of familiar words because it might optimally engage the broad receptive fields of the highest detectors in the hierarchical system for visual word recognition.

In pursuit of off-task thought: mind wandering-performance trade-offs while reading aloud and color naming

The present study investigated whether the frequency of probe-caught mind wandering varied by condition and had any impact on performance in both an item-by-item reading aloud task and a blocked version of the classic Stroop task. Across both experiments, mind wandering rates were found to be quite high and were negatively associated with vocal onset latencies and error rates across conditions. Despite this however, we observed poor correspondence between the effects of task demands on mind wandering rates and the effects of mind wandering on primary task performance. We discuss these findings in relation to attentional resource accounts of mind wandering and suggest that individuals can adjust the relative distribution of executive/attentional resources between internal and external goals in a way that maximizes off-task thought while preserving primary task performance.

The effect of target context and cue type in a postcue word pronunciation task

Dallas and Merikle (1976a, 1976b) demonstrated that when participants were presented with a pair of words for over 1 s and subsequently cued to pronounce one of the words aloud (postcue task) semantic priming effects occurred. Humphreys, Lloyd-Jones, and Fias (1995) failed to replicate this postcue semantic priming effect using word pairs that were semantic category co-ordinates. The aim of Experiment 1 was to determine if the disparate postcue task results reported by these researchers could be accounted for by the prime-target contexts or cue types engaging different attentional processes or a combination of these factors. A postcue pronunciation task was used and word pairs presented were taken from an associate-semantic context and a semantic category context. In the Dallas and Merikle condition the line cue flanked the location in which the target word was previously shown. In the Humphreys et al. condition the cue word UPPER or lower was centrally presented and indicated the location in which the target word previously appeared. Results demonstrated that the occurrence of semantic and associate-semantic priming effects under postcue task conditions varied for the two cue types. Experiment 2 investigated if these results were attributable to a between subject manipulation of cue type. Using a fully repeated measures design priming effects were evident for top located targets in both the associate-semantic and semantic prime-target contexts. Experiment 3 used a between subjects design to rule out the possibility that carry over effects between cue and context conditions contributed to the postcue task priming effects. Priming was evident for top located targets in an associate-semantic and semantic context for the line cue. For the word cue there was priming for top located targets from an associate-semantic context and a reverse priming effect for top located targets from the semantic context. Possible explanations for the occurrence of priming effects under postcue task conditions are discussed.

The interdependence of spatial attention and lexical access as revealed by early asymmetries in occipito-parietal ERP activity

A test of the possible functional interaction between mechanisms subserving spatial attention and lexical access was devised by displaying one green and one red string of letters, one to the left and one to the right of fixation, and having participants attend to a target string defined by color while ignoring the other distractor string. The target string for a delayed lexical decision task could be a word or a nonword. The distractor was always a word. When the target was a word, target and distractor were associatively related on half of the trials and not related in the other trials. The event-related potential time-locked to the onset of the letter strings produced an N2pc (a greater negativity at scalp sites contralateral to the target relative to the ipsilateral sites arising at about 170 ms poststimulus). N2pc amplitude was reduced when the words were related relative to when they were not related. The results provide direct, online evidence that the rapid activation of meaning by visual words can influence the efficiency of the deployment of spatial attention.

Perceptual implicit memory relies on intentional, load-sensitive processing at encoding

In two experiments, we examined whether the encoding processes leading to perceptual implicit memory satisfied the intentionality and load insensitivity criteria for automaticity. Whether participants intended to process words or digits, in displays containing both, was manipulated in Experiment 1. Results showed an effect of intention on a subsequent perceptual identification task and a recognition task. Load (one, two, and four words) and exposure duration (1,000, 600, and 200 msec) at encoding were manipulated in Experiment 2. Recognition was affected by both variables, but performance on the perceptual identification task was affected only by load. In both experiments, the results showed that controlled (intentional, load-sensitive) processing of words at encoding is essential for later perceptual implicit memory. That is, the encoding processes leading to perceptual implicit memory fail both criteria of automaticity.

Perceptual implicit memory requires attentional encoding

Perceptual implicit memory for previously attended and unattended words was measured either in a word-stem completion task or in a perceptual fluency (perceptual identification) task. Subjects (N = 144) first engaged in a focused attention task in which they were to identify one of two words presented for 100, 200, or 300 msec. Words were classified as attended if they were reported during the focused attention task and unattended if they were not. Results for both implicit memory tests indicated reliable perceptual implicit memory for attended words but not for unattended words, regardless of focused attention exposure duration. The results indicate that perceptual implicit memory tasks reflect attentional encoding processes; that is, words must undergo attentional encoding if they are to affect performance on a later perceptual implicit memory test.