A developmental, interactive activation model of the word superiority effect

Parallel distributed processing (PDP) models of reading developed out of an appreciation of the role that context plays in letter and word perception. Adult readers can more accurately identify letters in a word than alone or in other random display contexts, a phenomenon known as the Word Superiority Effect (WSE). We examined the effects of orthographic context on the letter recognition skills of dyslexic children, comparing their performance to adults, and chronological- and reading-age matched groups. Consistent with previous studies, results showed adults better able to identify letters in the context of words and pseudowords than in random letter strings. Young normal readers demonstrated the WSE, but their pseudoword advantage was less than adults. The dyslexic children showed no WSE at all. PDP computer simulations for the experimental data using the Interactive Activation model (IA) suggested that the orthographic components of the lexical system of normal children are interactive and distributed as they are in adults but provide less bottom-up activation. In addition, top-down processing increases with age and reading skill, but may be absent for dyslexic readers.     

Parafoveal processing of words and saccade computation during eye fixations in reading

Studied parafoveal word processing during eye fixations in reading to answer two questions: (a) Is the processing of parafoveally available words limited to the identification of beginning letters? (b) Does the parafoveal processing of words affect the following interword saccade? Reading afforded either no parafoveal preview, preview of beginning trigrams, preview of ending trigrams, or preview of the whole parafoveal word. Previews were controlled by replacing original letters either with X's or dissimilar letters. Preview benefits were larger for the whole word previews than for beginning or ending trigram previews. X-masks yielded preview benefits from intact beginning and ending trigrams but dissimilar letter masks yielded benefits from beginning trigrams only. Saccades were larger for whole word previews than for no previews. These results support Logogen-type models of word recognition and a model of saccade computation that posits a time-locked functional relation between the acquisition of parafoveal word information and the positioning of each fixation.     

Effects of Output Order on Hemispheric Asymmetry for Processing Letter Trigrams

Observers identified consonant–vowel–consonant trigrams with the letters arranged vertically by pronouncing the stimulus (treating the bottom letter as the first letter) and spelling it from bottom to top. On each trial, the trigram was presented to the left visual field/right hemisphere (LVF/RH), to the right visual field/left hemisphere (RVF/LH), or to both visual fields simultaneously (BILATERAL trials). Quantitative and qualitative visual field differences were identical to those found when observers used a more natural response output order, treating the top letter of the trigram as the first letter. The results suggest that, regardless of output order, attention is distributed across the three letters in a relatively slow, top-to-bottom fashion on LVF/RH and BILATERAL trials, whereas attention is distributed more rapidly and evenly across the three letters on RVF/LH trials.     

Absence of lexical and orthographic effects in a same-different task

Two experiments are reported that investigate whether the lexical and orthographic effects typically found in a simultaneous matching task are due to the facilitating effect of linguistic context on letter identification. The first experiment used a delayed matching task (2-sec SOA), with serial incremental display of the letters of the second stimulus (e.g., B, BR, BRA, BRAI, BRAIN). Lexical and orthographic effects were clearly demonstrated when the letters of the second stimulus were displayed rapidly (40 msec/letter), but these effects were absent at a slower speed (400 msec/letter). The same results were obtained in a second experiment, in which the letters of both stimuli were synchronously presented at either the fast rate or the slow rate. These results were interpreted in terms of a multilevel race model that assumes no interaction between levels of processing and attributes the effects to differing degrees of decision-processing lag.     

The role of lateral masking and orthographic structure in letter and word recognition.

The present experiments evaluated the contribution of orthographic structure and lateral masking in the perception of letter, word, and nonword test displays. Performance was tested in a backward recognition masking experiment in which a masking stimulus followed the test display after a variable blank interstimulus interval. In agreement with previous findings across different experiments, words were recognized better than single letterd at short interstimulus intervals, but the opposite was the case at long intervals. Performance on the nonwords resembled performance on letters at short masking intervals and performance on words at long masking intervals. The quantitative results were described by a processing model that incorporates the effects of lateral masking and orthographic structure in the dynamic processing of letter strings. Lateral masking tends to lower the potential perceptibility of letters whereas orthographic structure can reduce the uncertainty of the candidate letters in the letter sequence. The present model predicts that the quantitative contribution of each of these processes to performance is critically dependent upon the processing time available before the onset of the masking stimulus.     

The category effect in visual search depends on physical rather than conceptual differences

Is a target letter (digit) more readily detected in a digit (letter) background because of conceptual-level differences between letters and digits or because of physical-level differences? When letters and digits were matched on physical features, both for the target set and the background set, no letter vs. digit category effect was found. With physical differences eliminated, search was faster and more accurate for letter than for digit targets and distractors, presumably because of the greater familiarity of letters. Presenting the same characters in normal and mirrorreversed orientation, which also minimized featural differences between categories, produced only a small normal vs. reversed category effect. In a normal background, a reversed target lost much more from its unfamiliarity than it gained from mismatching the background. The present results indicate that the category effect vanishes when only conceptual level differences are present.     

The word-superiority effect does not require a T-scope

Six experiments examined the possibility of obtaining a word-superiority effect (WSE) without the use of brief stimulus exposures or a poststimulus mask. In each experiment, subjects were presented a stimulus string and two alternative strings that differed by a single letter (Reicher, 1969). The alternatives and stimulus remained in view until subjects responded, and subjects were under no pressure to respond quickly. In Experiments 1–3, the stimuli were presented in very small type so that they were difficult to see. Subjects were significantly more accurate with words than with nonwords, letters embedded among digits, or letters embedded among number signs (#s). In Experiments 4 and 5, the stimuli were embedded in a simultaneously present pattern mask. Subjects were significantly more accurate with words than with single letters by themselves. In the final experiment, the stimuli were presented in a mask with specific spatial frequency characteristics, and performance was significantly better with words than with nonwords. The WSE is a more general phenomenon than previously supposed; it is not limited to a tachistoscopic exposure.     

The word-superiority effect does not require a T-scope.

Six experiments examined the possibility of obtaining a word-superiority effect (WSE) without the use of brief stimulus exposures or a poststimulus mask. In each experiment, subjects were presented a stimulus string and two alternative strings that differed by a single letter (Reicher, 1969). The alternatives and stimulus remained in view until subjects responded, and subjects were under no pressure to respond quickly. In Experiments 1-3, the stimuli were presented in very small type so that they were difficult to see. Subjects were significantly more accurate with words than with nonwords, letters embedded among digits, or letters embedded among number signs (#s). In Experiments 4 and 5, the stimuli were embedded in a simultaneously present pattern mask. Subjects were significantly more accurate with words than with single letters by themselves. In the final experiment, the stimuli were presented in a mask with specific spatial frequency characteristics, and performance was significantly better with words than with nonwords. The WSE is a more general phenomenon than previously supposed; it is not limited to a tachistoscopic exposure.     

Preschoolers' knowledge about the appearance of proper names

Preschoolers' knowledge of the appearance of proper names was tested in three experiments with 25 boys and 22 girls from low-income families. Children from a Head Start program, whose parents signed a permission letter, participated. Their ages ranged from 3 yr. 6 mo. to 5 yr. 6 mo. (M = 52.2 mo., SD = 4.9). When shown consonant-vowel-consonant trigrams such as Rit or baF or dEg with various capitalization patterns, the children showed a tendency to recognize that CVC trigrams with the first letter capitalized or all letters capitalized were the ones most likely to represent a person's name. When their own names were substituted, which typically contained more than three letters, their performance was markedly better. Children also had a strong tendency to consider trigrams of Latin letters as more likely to be a person's name than trigrams of non-Latin characters (e.g., Sanskrit).     

Parafoveal letter-position coding in reading

The masked-priming lexical decision task has been the paradigm of choice for investigating how readers code for letter identity and position. Insight into the temporal integration of information between prime and target words has pointed out, among other things, that readers do not code for the absolute position of letters. This conception has spurred various accounts of the word recognition process, but the results at present do not favor one account in particular. Thus, employing a new strategy, the present study moves out of the arena of temporal- and into the arena of spatial information integration. We present two lexical decision experiments that tested how the processing of six-letter target words is influenced by simultaneously presented flanking stimuli (each stimulus was presented for 150 ms). We manipulated the orthographic relatedness between the targets and flankers, in terms of both letter identity (same/different letters based on the target’s outer/inner letters) and letter position (intact/reversed order of letters and of flankers, contiguous/noncontiguous flankers). Target processing was strongly facilitated by same-letter flankers, and this facilitatory effect was modulated by both letter/flanker order and contiguity. However, when the flankers consisted of the target’s inner-positioned letters alone, letter order no longer mattered. These findings suggest that readers may code for the relative position of letters using words’ edges as spatial points of reference. We conclude that the flanker paradigm provides a fruitful means to investigate letter-position coding in the fovea and parafovea.     

The primacyof visual information inthe analysis of letter strings

In Experiment 1, orthographic and phonetic information were separated by using artificial letters to represent English pseudowords and random letter strings. Subjects could learn to distinguish combinations of artificial letters on the basis of (1) orthographic, but not phonetic, information, (2) orthographic and phonetic information, (3) paired-associate verbal labels without orthographic information, and (4) neither orthographic nor phonetic information. By imposing a variety of response deadlines it appeared that subjects quickly exploited orthographic information without any contribution from phonetic correspondences. The only suggestion of a phonetic effect occurred in the absence of orthographic information and at longer latencies. Experiment 3 (using English letters) also suggested that phonetic information influenced the analysis of letter string pairs at only longer latencies, after visual analysis. Experiment 2 provided a demonstration that orthographic rules similar to those exploited in Experiment 1 were useful in visual discriminations regardless of the particular letter position affected by those rules. The results strain phonetic mediation models of performance in word-related tasks (e. g., Spoehr & Smith, 1975)and support models that emphasize visual analysis(Barron & Baron, 1977; Massaro, 1975; Pollatsek, Well, & Schindler, 1975).     

The Word Superiority Effect in central and peripheral vision

The Word Superiority Effect (WSE) is a well-known phenomenon in reading research, where words are reported more accurately than single letters or non-words. We report two experiments that investigate the WSE in the central and peripheral visual field, as well as laterality differences in the perception of words and letters, using methods based on the Theory of Visual Attention. The results show a WSE in the central visual field, reflected in mean scores, perception thresholds, and processing speed, whereas the effect is eliminated or reversed in the periphery. This may be caused by crowding, which prevents lexical analysis of a word in the periphery. We conclude that perception of words and letters differs according to location in the visual field. Linking our results to previous studies of crowding effects in patients with reading impairments, we hypothesize that similar mechanisms may limit normal word peripheral processing.     

The role of orthographic and phonological codes in the word and the pseudoword superiority effect: an analysis by means of multinomial processing tree models

Central to the current accounts of the word and the pseudoword superiority effect (WSE and PWSE, respectively) is the concept of a unitized code that is less susceptible to masking than single-letter codes. Current explanations of the WSE and PWSE assume that this unitized code is orthographic, explaining these phenomena by the assumption of dual read-out from unitized and single-letter codes. In this article, orthographic dual read-out models are compared with a phonological dual read-out model (which is based on the assumption that the 1st unitized code is phonological). From this phonological code, an orthographic code is derived, through either lexical access or assembly. Comparison of the orthographic and phonological dual read-out models was performed by formulating both models as multinomial processing tree models. From an application of these models to the data of 2 letter identification experiments, it was clear that the orthographic dual read-out models are insufficient as an explanation of the PWSE, whereas the phonological dual read-out model is sufficient.     

Orthographic similarity: The case of “reversed anagrams”

How orthographically similar are words such as paws and swap, flow and wolf, or live and evil? According to the letter position coding schemes used in models of visual word recognition, these reversed anagrams are considered to be less similar than words that share letters in the same absolute or relative positions (such as home and hose or plan and lane). Therefore, reversed anagrams should not produce the standard orthographic similarity effects found using substitution neighbors (e.g., home, hose). Simulations using the spatial coding model (Davis, Psychological Review 117, 713-758, 2010), for example, predict an inhibitory masked-priming effect for substitution neighbor word pairs but a null effect for reversed anagrams. Nevertheless, we obtained significant inhibitory priming using both stimulus types (Experiment 1). We also demonstrated that robust repetition blindness can be obtained for reversed anagrams (Experiment 2). Reversed anagrams therefore provide a new test for models of visual word recognition and orthographic similarity.     

Reading through a noisy channel: why there's nothing special about the perception of orthography

The goal of research on how letter identity and order are perceived during reading is often characterized as one of "cracking the orthographic code." Here, we suggest that there is no orthographic code to crack: Words are perceived and represented as sequences of letters, just as in a dictionary. Indeed, words are perceived and represented in exactly the same way as other visual objects. The phenomena that have been taken as evidence for specialized orthographic representations can be explained by assuming that perception involves recovering information that has passed through a noisy channel: the early stages of visual perception. The noisy channel introduces uncertainty into letter identity, letter order, and even whether letters are present or absent. We develop a computational model based on this simple principle and show that it can accurately simulate lexical decision data from the lexicon projects in English, French, and Dutch, along with masked priming data that have been taken as evidence for specialized orthographic representations.     

Scanning,holistic encoding,and the word-superiority effect

The role of holistic encoding induced by scanning in the superior identifiability target letters in orthographic strings (words) enjoy over those in strings of unrelated letters was examined in two experiments. Both the set of potential targets and the critical position in the letter arrays were predesignated. One group in each experiment was induced to scan each array from left to right in a dot-counting task. A dot could precede the array to its left and/or appear with the array to its right. Only this group displayed the word superiority. For the second group in the first experiment, any dot(s) present always appeared with the array. The second group in the second experiment was shown no dots but, rather, performed the letter-identification task only. The absence of a word-superiority effect in other studies is related to holistic encoding stemruing from scanning requirements, and the implications for positional uncertainty explanations of the phenomenon are discussed.     

Children read normal and reversed letters: A simple test of reading skill

Above- and below-average readers in grades 3, 5 and 7 named letters under two conditions. In one condition, letters were presented in normal orientation. In the other condition, letters were presented in left-right mirror image orientation. The ratio of (1) naming time on normal letters to (2) naming time on mirror image letters was calculated for each child. Good readers had lower ratios than poor readers. This was due primarily to the faster naming of normal letters by good readers. Good and poor readers named mirror image letters at similar speeds. Two possible explanations for the results are discussed. One explanation is that the skilled readers have a better memory for the normal orientation of the letter shapes. A second explanation is that skilled readers process more peripheral information, when naming, than their less skilled counterparts, but that this peripheral processing is curtailed when transformed text is presented.     

Do transposed-letter similarity effects occur at a prelexical phonological level?

Nonwords created by transposing two letters (e.g., RELOVUTION) are very effective at activating the lexical representation of their base words (Perea & Lupker, 2004). In the present study, we examined whether the nature of transposed-letter (TL) similarity effects was purely orthographic or whether it could also have a phonological component. Specifically, we examined transposed-letter similarity effects for nonwords created by transposing two nonadjacent letters (e.g., relovución-REVOLUCION) in a masked form priming experiment using the lexical decision task (Experiment 1). The controls were (a) a pseudohomophone of the transposed-letter prime (relobución-REVOLUCION; note that B and V are pronounced as /b/ in Spanish) or (b) an orthographic control (relodución-REVOLUCION). Results showed a similar advantage of the TL nonword condition over the phonological and the orthographic control conditions. Experiment 2 showed a masked phonological priming effect when the letter positions in the prime were in the right order. In a third experiment, using a single-presentation lexical decision task, TL nonwords produced longer latencies than the orthographic and phonological controls, whereas there was only a small phonological effect restricted to the error data. These results suggest that TL similarity effects are orthographic--rather than phonological--in nature.     

Are individual or consecutive letters the unit affected by repetition blindness?

When 2 similar words (e.g., react reach) are briefly sequentially displayed, the 2nd word may be omitted from the report, a phenomenon known as repetition blindness (RB). Previous researchers have suggested that consecutive letters are the unit affected by RB. Six experiments provided new data on orthographic RB. Two letters at the beginning or end of words resulted in RB, as did alternating interior letters (tactile earthly) and 3 letters with different relative positions (arid bird). However, no RB was found with a single final letter (show view). Observed RB may reflect pattern completion because RB for pairs like throat theory was reduced when the nonrepeated letters (eory) were consistent with only a single word. The experiments point to a model of orthographic RB in which both individual letters and letter sequences of length 2 or more play a role.