Spatial interaction effects in letter processing

The hypothesis of independent processing channels was tested in a letter-recognition task. Letter space and retinal position were varied for both unilateral and bilateral presentations of two-letter configurations. The response latencies indicated contour interference effects for small letter spaces as well as a different type of processing delay which increased rapidly with increased letter distance from the fixation point. The latter effect was assumed to represent an interaction between the feature extraction processes of the adjacent letters. Since the processing capacity decreases as a function of the distance from the fovea, the reaction times were correspondingly lengthened.     

Changes in letter processing in beginning readers

Letter pairs were tachistoscopically presented to children from grades 1, 2 and 6 (85.6, 99.4, and 147.8 months of age, respectively). They were required to determine whether the letters had a same name by pressing one of two response keys as fast as possible. Also a letter detection task was presented where letter matching was either based on physical or name characteristics. The name match in both tasks was slower than the match of letters which shared the same visual form. The name-physical match differences changed significantly as a function of grade level. Shifts in latency differences over grades can be considered as a fundamental correlate of reading ability. Children increasingly employ strategies of processing based on nominal cues and become efficient in extracting the invariant features of letters amongst irrelevant variations such as type face.     

Dual hemispheric processing in a letter matching task

It has been reported that performance on recognition, detection, and matching tasks is enhanced if stimuli are projected to both sides of the visual field rather than to one side alone (Dimond, 1972). The present study investigated the claim that this phenomenon is due to the distribution of the burden of perceptual processing between the hemispheres. Three experiments were carried out using a matching paradigm in which RT and response errors were recorded. In all experiments, subjects were required to match two letters that were displayed separately on either side of a central fixation point (bilateral presentation) or were displayed together on the same side of the visual field (unilateral presentation). It was found that although lateral interference between adjacent stimuli was significantly implicated in the phenomenon, a strong residual effect, which could be tentatively ascribed to hemispheric mechanisms, remained in relation to letter name matches. It is argued that a model based on parallel hemispheric decision processes provides a better account of the data than does one based upon the notion of distributed perceptual processing.     

The processing of consonants and vowels during letter identity and letter position assignment in visual-word recognition: an ERP study

Recent research suggests that there is a processing distinction between consonants and vowels in visual-word recognition. Here we conjointly examine the time course of consonants and vowels in processes of letter identity and letter position assignment. Event related potentials (ERPs) were recorded while participants read words and pseudowords in a lexical decision task. The stimuli were displayed under different conditions in a masked priming paradigm with a 50-ms SOA: (i) identity/baseline condition e.g., chocolate-CHOCOLATE); (ii) vowels-delayed condition (e.g., choc_l_te-CHOCOLATE); (iii) consonants-delayed condition (cho_o_ate-CHOCOLATE); (iv) consonants-transposed condition (cholocate-CHOCOLATE); (v) vowels-transposed condition (chocalote-CHOCOLATE), and (vi) unrelated condition (editorial-CHOCOLATE). Results showed earlier ERP effects and longer reaction times for the delayed-letter compared to the transposed-letter conditions. Furthermore, at early stages of processing, consonants may play a greater role during letter identity processing. Differences between vowels and consonants regarding letter position assignment are discussed in terms of a later phonological level involved in lexical retrieval.     

The effects of forced serial processing on identification of words and random letter strings

Skilled readers identified words and random letter strings displayed one letter at a time on the screen of a computer-controlled oscilloscope. Letters were either displayed in a single position, or painted left-to-right in adjacent positions. Adjacent displays were either unmasked, masked by a letter-like pattern following each letter (backward masking) or masked by a pattern preceding each letter (forward masking). Unmasked words were identified with a high degree of accuracy, and accuracy was independent of the exposure duration of the letters over the range 50–200 msec. Masked adjacent word displays and one-position word displays were identified much less accurately, and accuracy was highly dependent on letter exposure duration. In contrast to these results, identification of random strings, or of letters within random strings, was almost unaffected by the presence of the mask and was dependent on letter exposure duration under all display conditions. The results are interpreted as evidence that (a) masking forces subjects to process serial displays one letter at a time, and (b) words, or large segments of words, are habitually processed in parallel, while random strings are processed as a series of individual letters or small chunks.     

Learning letter names and sounds: Effects of instruction, letter type, and phonological processing skill

Preschool-age children (N = 58) were randomly assigned to receive instruction in letter names and sounds, letter sounds only, or numbers (control). Multilevel modeling was used to examine letter name and sound learning as a function of instructional condition and characteristics of both letters and children. Specifically, learning was examined in light of letter name structure, whether letter names included cues to their respective sounds, and children’s phonological processing skills. Consistent with past research, children receiving letter name and sound instruction were most likely to learn the sounds of letters whose names included cues to their sounds regardless of phonological processing skills. Only children with higher phonological skills showed a similar effect in the control condition. Practical implications are discussed.     

The development of complex sentence processing strategies

Children aged 3, 4, and 5 years and adults heard sentences with clauses connected by after, and, or before, saw a picture, and indicated whether or not the picture matched one of the events of the sentence. Response times were taken as a measure of immediate accessibility to the meaning of the clause that the picture was about. Temporal organization of sentence meanings was dominant in 3-year-olds and adults, but not in 4- or 5-year-olds. The 3-year-olds and especially the adults processed and-sentences as implicitly temporal. The results for 4- and 5-year-olds are interpreted as indicating experimentation with alternate strategies for organizing sentences based on the structural/presuppositional properties of clauses.     

Differentiation of holistic processing in the time course of letter recognition

Pairs of letters, pseudo-letters, and basic geometrical shapes were presented in a sequential same-different task, in which the time between the first and second items was varied. The second item was either presented in isolation or surrounded by an irrelevant geometrical shape that could be congruent or incongruent to the target. Congruence effects were obtained for shapes and pseudo-letters, but not for letters if the interval between the first and second items was short. Absence of congruence effects was interpreted, in accordance with earlier findings, as categorical influence on early visual integration processes; letters are processed less holistically than non-letter shapes. The present result indicates that categorical influence of letters depends on the time course of stimulus processing. As a highly automatized process, it is effective for stimuli appearing at a relatively fast rate, whereas, a slower rate of stimulus presentation eliminates task-irrelevant categorical influences.     

Forced serial processing of words and letter strings: A reexamination

Words and nonword strings, three and seven letters long, were displayed serially (i.e., one letter at a time) or simultaneously, with or without a backward mask following display of each letter or string. Recognition of words, and of individual letters within words, was markedly impaired in the masked serial condition relative to the unmasked serial, unmasked simultaneous, and masked simultaneous conditions. Analogous differences were smaller or nonexistent for seven-letter nonwords; however, three-letter nonwords produced relatively “wordlike” data. Implications for the issue of spatially serial vs. parallel processing in word recognition are discussed.     

The development of emotional face processing during childhood

Our facial expressions give others the opportunity to access our feelings, and constitute an important nonverbal tool for communication. Many recent studies have investigated emotional perception in adults, and our knowledge of neural processes involved in emotions is increasingly precise. Young children also use faces to express their internal states and perceive emotions in others, but little is known about the neurodevelopment of expression recognition. The goal of the current study was to determine the normal development of facial emotion perception. We recorded ERPs in 82 children 4 to 15 years of age during an implicit processing task with emotional faces. Task and stimuli were the same as those used and validated in an adult study; we focused on the components that showed sensitivity to emotions in adults (P1, N170 and frontal slow wave). An effect of the emotion expressed by faces was seen on the P1 in the youngest children. With increasing age this effect disappeared while an emotional sensitivity emerged on N170. Early emotional processing in young children differed from that observed in the adolescents, who approached adults. In contrast, the later frontal slow wave, although showing typical age effects, was more positive for neutral and happy faces across age groups. Thus, despite the precocious utilization of facial emotions, the neural processing involved in the perception of emotional faces develops in a staggered fashion throughout childhood, with the adult pattern appearing only late in adolescence.     

Developmental trajectory of neural specialization for letter and number visual processing

Adult neuroimaging studies have demonstrated dissociable neural activation patterns in the visual cortex in response to letters (Latin alphabet) and numbers (Arabic numerals), which suggest a strong experiential influence of reading and mathematics on the human visual system. Here, developmental trajectories in the event‐related potential (ERP) patterns evoked by visual processing of letters, numbers, and false fonts were examined in four different age groups (7‐, 10‐, 15‐year‐olds, and young adults). The 15‐year‐olds and adults showed greater neural sensitivity to letters over numbers in the left visual cortex and the reverse pattern in the right visual cortex, extending previous findings in adults to teenagers. In marked contrast, 7‐ and 10‐year‐olds did not show this dissociable neural pattern. Furthermore, the contrast of familiar stimuli (letters or numbers) versus unfamiliar ones (false fonts) showed stark ERP differences between the younger (7‐ and 10‐year‐olds) and the older (15‐year‐olds and adults) participants. These results suggest that both coarse (familiar versus unfamiliar) and fine (letters versus numbers) tuning for letters and numbers continue throughout childhood and early adolescence, demonstrating a profound impact of uniquely human cultural inventions on visual cognition and its development.     

The involvement of letter names in the silent processing of isolated letters: A developmental perspective

This study was designed to clarify the nature of the mental representations underlying the processing of letters. A total of 96 Hebrew readers randomly recruited from three levels of education were asked to make rapid same/different judgments for Hebrew letter dyads with monosyllabic and bisyllabic names. The results obtained from the performance of participants under perceptual and conceptual processing conditions suggest that Hebrew readers access nominal letter representations in order to mediate letter processing in tasks that cannot be resolved on the basis of a sheer perceptual analysis of the letters?? visual properties. The finding that the retrieval of nominal letter representations was evident for participants who differed rather markedly in their letter-processing speeds highlights the central role of letter names in the processing of isolated letters.     

The independence of letter identity and letter doubling in reading

The ability to read requires processing the letter identities in the word and their order, but it is by no means obvious that our long-term memory representations of words spellings consist of only these dimensions of information. The current investigation focuses on whether we process information about another dimension—letter doubling (i.e., that there is a double letter in WEED)—independently of the identity of the letter being doubled. Two experiments that use the illusory word paradigm are reported to test this question. In both experiments, participants are more likely to misperceive a target word with only singleton letters (e.g., WED) as a word with a double (e.g., WEED) when the target is presented with a distractor that contains a different double letter (e.g., WOOD) than when the distractor does not contain a double letter (e.g., WORD). This pattern of results is not predicted by existing computational models of word reading but is consistent with the hypothesis that written language separately represents letter identity and letter doubling information, as previously shown in written language production. These results support a view that the orthographic representations that underlie our ability to read are internally complex and suggest that reading and writing rely on a common level of orthographic representation.     

Visual experiences during letter production contribute to the development of the neural systems supporting letter perception

Letter production through handwriting creates visual experiences that may be important for the development of visual letter perception. We sought to better understand the neural responses to different visual percepts created during handwriting at different levels of experience. Three groups of participants, younger children, older children, and adults, ranging in age from 4.5 to 22 years old, were presented with dynamic and static presentations of their own handwritten letters, static presentations of an age‐matched control's handwritten letters, and typeface letters during fMRI. First, data from each group were analyzed through a series of contrasts designed to highlight neural systems that were most sensitive to each visual experience in each age group. We found that younger children recruited ventral‐temporal cortex during perception and this response was associated with the variability present in handwritten forms. Older children and adults also recruited ventral‐temporal cortex; this response, however, was significant for typed letter forms but not variability. The adult response to typed letters was more distributed than in the children, including ventral‐temporal, parietal, and frontal motor cortices. The adult response was also significant for one's own handwritten letters in left parietal cortex. Second, we compared responses among age groups. Compared to older children, younger children demonstrated a greater fusiform response associated with handwritten form variability. When compared to adults, younger children demonstrated a greater response to this variability in left parietal cortex. Our results suggest that the visual perception of the variability present in handwritten forms that occurs during handwriting may contribute to developmental changes in the neural systems that support letter perception.     

The associated nontargets effect: Evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

The associated non-targets effect: evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

Effects of test anxiety on motor learning: The processing efficiency hypothesis

Abstract

The hypothesis that, under test (stress) conditions, high trait-anxious individuals invest extra processing resources to reach motor learning levels similar to those of low-anxious individuals was investigated. A transfer procedure (practice trial, rest interval, and transfer trial) was employed to analyse motor learning effects. In Experiment 1, a secondary task (click detection) was used to measure the extra processing resources expenditure on motor learning during the practice trial. Neither motor performance in the transfer trial nor secondary task performance differed as a function of test condition or anxiety trait. A critical analysis of the secondary task paradigm suggested that it was not sensitive enough to reflect the amount of processing capacity expended on the primary motor tasks. In Experiment 2, subjects performed a loading task (verbal shadowing of sentences) concurrently with the motor tasks during the practice trial to prevent extra resources from being allocated to motor learning. Results showed that anxiety trait was associated to performance time increments on the high-demanding motor tasks in the transfer trial. A plausible explanation is that anxiety impairs learning because it reduces the efficiency of processing. An alternative interpretation, concerning an ability deficit of high trait-anxious individuals, is discussed.     

Evidence from mutual masking for serial processing of tachistoscopic letter patterns.

This experiment deomonstrates serial processing of tachistoscopic patterns when all potential artifacts are eliminated. Two nonsense arrays of six letters were tachistoscopically exposed successively at the same positions. Ss identified more letters from the temporally first string on the left of fixation and more from the second on the right, indicating left-to-right serial processing. Variations among Ss in the location of the crossover in curves indicate individual differences in processing time. Therefore, this study demonstrates definitively that tachistoscopic performance at various positions can reflect a sequential left-to-right processing of information, possibly at different rates.