Orthographic contributions to perceived word center

We have a surprising tendency to misperceive the center of visually presented words (). To understand the origin of this bias, four experiments assessed the impact of letter font, letter size, and grapheme-phoneme convergences on perceived stimulus center. Fourteen observers indicated the perceived centers of words, pseudowords, consonant strings, and lines with a mouse cursor. Visual orthographic factors had no effect on perceived word center but grapheme-phoneme convergence did: Observers compensated for strong grapheme-phoneme asymmetries in the letter strings. These findings support the idea that the cognitive representation of words is spatially distorted as a result of lexical access mechanisms.     

The use of abstract graphemic information in lexical access

Three experiments investigated the nature of the information required for the lexical access of visual words. A four-field masking procedure was used, in which the presentation of consecutive prime and target letter strings was preceded and followed by presentations of a pattern mask. This procedure prevented subjects from identifying, and thus intentionally using, prime information. Experiment I extablished the existence of a semantic priming effect on target identification, demonstrating the lexical access of primes under these conditions. It also showed a word repetition effect independent of letter case. Experiment II tested whether this repetition effect was due to the activation of graphemic or phonemic information. The graphemic and phonemic similarity of primes and targets was varied. No evidence for phonemic priming was found, although a graphemic priming effect, independent of the physical similarity of the stimuli, was obtained. Finally Experiment III demonstrated that, irrespective of whether the prime was a word or a nonword, graphemic priming was equally effective. In both Experiments II and III, however, the word repetition effect was stronger than the graphemic priming effect. It is argued that facilitation from graphemic priming was due to the prime activating a target representation coded for abstract (non-visual) graphemic features, such as letter identities. The extra facilitation from same identity priming was attributed to semantic as well as graphemic activation. The implications of these results for models of word recognition are discussed.     

Phonemic priming with words and pseudowords

Abstract

The bi-alphabetic nature of the Serbo-Croatian writing system allows unequivocal examination of phonemic similarity unconfounded with graphemic similarity. The Roman and Cyrillic alphabets are largely independent but map onto the same sounds. A lower-case context written in one alphabet bears no visual similarity to an uppercase target written in the other alphabet. One naming experiment and one lexical decision experiment investigated phonemic priming of high-frequency words and pseudowords with word and pseudoword contexts. For naming, targets that were phone-mically similar to the preceding context were named significantly faster than were phonemically dissimilar targets. This result was indifferent to the lexicality of the contexts and targets. For lexical decision, in contrast, phonemically similar word-word pairs showed inhibition, whereas phonemically similar pseudoword-word pairs showed facilitation relative to their phonemically dissimilar counterparts. These results were discussed in terms of (1) a model of visual word processing that posits a layer of phoneme units between letter units and word units, and (2) the idea that active word units inhibit one another in proportion to each one's frequency. In this account, phonemic similarity effects in naming are based on the states of the phoneme units, while phonemic similarity effects in lexical decision are based on the states of the word units. These results lend further support to the claim that, for readers of Serbo-Croatian, the visual computation of phonology is automatic and prelexical.     

Graphemic complexity and multiple print-to-sound associations in visual word recognition

It has recently been reported that words containing a multiletter grapheme are processed slower than are words composed of single-letter graphemes (Rastle & Coltheart, 1998; Rey, Jacobs, Schmidt-Weigand, & Ziegler, 1998). In the present study, using a perceptual identification task, we found in Experiment 1 that this graphemic complexity effect can be observed while controlling for multiple print-to-sound associations, indexed by regularity or consistency. In Experiment 2, we obtained cumulative effects of graphemic complexity and regularity. These effects were replicated in Experiment 3 in a naming task. Overall, these results indicate that graphemic complexity and multiple print-to-sound associations effects are independent and should be accounted for in different ways by models of written word processing.     

Is there a temporal basis of the word length effect? A response to Service (1998)

Service (1998) carried out a study of the word length effect with Finnish pseudowords in which short and long pseudowords were identical except for the inclusion of certain phonemes differing only in pronunciation length, a manipulation that is impossible in English. She obtained an effect of phonemic complexity but little or no word duration effect per se - a discrepancy from the expectations generated by the well-known working memory model of Baddeley (1986). In the present study using English words, we controlled for phonemic complexity differences by using the same words for the short- and long-word sets, but with instructions inducing shorter or longer pronunciation of the words. We obtained substantial word duration effects. Concerns raised by Service are addressed, and we conclude that both duration and complexity are likely to contribute to the word length effect in serial recall.     

Decreased Sensitivity to Phonemic Mismatch in Spoken Word Processing in Adult Developmental Dyslexia

Initial lexical activation in typical populations is a direct reflection of the goodness of fit between the presented stimulus and the intended target. In this study, lexical activation was investigated upon presentation of polysyllabic pseudowords (such as p rocodile for crocodile) for the atypical population of dyslexic adults to see to what extent mismatching phonemic information affects lexical activation in the face of overwhelming support for one specific lexical candidate. Results of an auditory lexical decision task showed that sensitivity to phonemic mismatch was less in the dyslexic population, compared to the respective control group. However, the dyslexic participants were outperformed by their controls only for word-initial mismatches. It is argued that a subtle speech decoding deficit affects lexical activation levels and makes spoken word processing less robust against distortion.     

Phonemic similarity effects and prelexical phonology

Ten experiments were conducted on visually presented Serbo-Croatian words and pseudowords, comprising phonemically similar and dissimilar context-target sequences. There were five main results. First, phonemic similarity effects in both lexical decision and naming are independent of graphemic similarity. Second, phonemic similarity need not facilitate lexical decision; the direction of its effect depends on lexicality, target frequency, and type of similarity (specifically, the position of the phoneme that distinguishes context and target). Third, phonemic similarity expedites the naming of words and pseudowords, and to the same degree. Fourth, phonemic similarity is negated in naming, but not in lexical decision, when the visually presented context and target are stressed differently. Fifth, the phonemic similarity effect occurs even when the context is a masked pseudoword. These results are discussed in terms of a model in which word-processing units are activated routinely by phoneme-processing units, and in which compositionally similar word units, when activated, inhibit one another in proportion to each's familiarity. In this model, the phonemic similarity effect in naming is based on the states of phoneme units, whereas the phonemic similarity effect in lexical decision is based on the states of word units. Overall, the results comport with an account in which phonology is computed prelexically and automatically.     

Word and Person Effects on Decoding Accuracy: A New Look at an Old Question

The purpose of this study was to extend the literature on decoding by bringing together two lines of research, namely person and word factors that affect decoding, using a crossed random-effects model. The sample was comprised of 196 English-speaking grade 1 students. A researcher-developed pseudoword list was used as the primary outcome measure. Because grapheme-phoneme correspondence (GPC) knowledge was treated as person and word specific, we are able to conclude that it is neither necessary nor sufficient for a student to know all GPCs in a word before accurately decoding the word. And controlling for word-specific GPC knowledge, students with lower phonemic awareness and slower rapid naming skill have lower predicted probabilities of correct decoding than counterparts with superior skills. By assessing a person-by-word interaction, we found that students with lower phonemic awareness have more difficulty applying knowledge of complex vowel graphemes compared to complex consonant graphemes when decoding unfamiliar words. Implications of the methodology and results are discussed in light of future research.     

Dissociation of mechanisms of reading in Alzheimer's disease.

The role of spelling-to-sound correspondence rules in oral word reading was investigated by asking patients with Alzheimer's Disease (AD) and normal controls to read aloud pronounceable letter strings that do not happen to be real words. These pseudowords were of two types: those that have orthographically similar "neighbors," and those that have no neighbors. The patients with AD were mildly impaired relative to the normal controls in reading pseudowords with neighbors, but were markedly impaired in reading pseudowords with no neighbors. The results are interpreted as favoring a model of reading in which words and pseudowords are normally read via the same lexical mechanism. An ancillary route involving the conscious application of spelling-to-sound rules is available only to cognitively intact readers.     

Differential backward masking of words and letters by masks of varying orthographic structure

The effects of structural relationships between targets and masks were investigated using a backward-masking paradigm. Specifically, the masking of single letters, common fiveletter words, and five-letter pseudowords masked by a blank flash, strings of overlapped letters, pseudowords, and words was investigated. Target duration was varied from 2 to 32 msec, with mask duration held constant at 25 msec. The dependent measure was the critical interstimulus interval for correct target identification. Letters were more effectively masked than words and pseudowords. A blank mask caused the least amount of masking, followed by the overlapped letter strings, and then the word and pseudoword masks. In addition to the overall greater masking effectiveness for the three patterned masks, overlapped letter strings masked letters more effectively than they did words. The implications of current theories of masking for these results and the implications of these results for theories of word recognition were discussed.     

The frequency effect for pseudowords in the lexical decision task

Four experiments were designed to investigate whether the frequency of words used to create pseudowords plays an important role in lexical decision. Computational models of the lexical decision task (e.g., the dual route cascaded model and the multiple read-out model) predict that latencies to low-frequency pseudowords should be faster than latencies to high-frequency pseudowords. Consistent with this prediction, results showed that when the pseudowords were created by replacing one internal letter of the base word (Experiments 1 and 3), high-frequency pseudowords yielded slower latencies than low-frequency pseudowords. However, this effect occurred only in the leading edge of the response time (RT) distributions. When the pseudowords were created by transposing two adjacent internal letters (Experiment 2), high-frequency pseudowords produced slower latencies in the leading edge and in the bulk of the RT distributions. These results suggest that transposed-letter pseudowords may be more similar to their base words than replacement-letter pseudowords. Finally, when participants performed a go/no-go lexical decision task with one-letter different pseudowords (Experiment 4), high-frequency pseudowords yielded substantially faster latencies than low-frequency pseudowords, which suggests that the lexical entries of high-frequency words can be verified earlier than the lexical entries of low-frequency words. The implications of these results for models of word recognition and lexical decision are discussed.     

Detection of intraword and interword letter repetition: A test of the word unitization hypothesis

Do words, as familiar units or gestalts, tend to swallow up and conceal their letter components (Pillsbury, 1897)? Letters typically are detected faster and more accurately in words than in nonwords (i.e., scrambled collections of letters), and in more frequent words than in less frequent words. However, a word advantage at encoding, where the representation of the string is formed, might compensate for, and thus mask, a word disadvantage at decoding and comparison, where the component letters of the representation are accessed and compared with the target letter. To better reveal any such word disadvantage, a task was used in this study that increased the amount of letter processing. Subjects judged whether a letter was repeated within a six-letter word or a nonword (Experiment 1; intraword letter repetition) or was repeated between two adjacent unrelated six-letter words or nonwords (Experiment 2; interword letter repetition). Contrary to Pillsbury's word unitization hypothesis, both types of letter repetition (intraword and interword) were detected faster and just as accurately with words as with nonwords. In Experiment 2, however, interword letter repetition was detected less accurately on common words (but not on rare words or third-order pseudowords) than on the corresponding nonwords. Thus, although the familiar word does not deny access to its own component letters, it does make their comparison with letters from other words more difficult.     

Preliminary letter identification in the perception of words and nonwords.

Words with mixed uppercase and lowercase letters (e.g. fAdE) were perceived more accurately than mixed-case pseudowords (e.g. gAdE), and mixed-case pseudowords were perceived more accurately than mixed-case unrelated letter strings (e.g. eFdT). In addition, same-case words were perceived more accurately than their mixed-case counterparts. The same held true for pseudowords but not for unrelated letter strings. The results are compatible with the view that both letter identify and visual form information are used in word perception.     

Degree of illiteracy and phonological and metaphonological skills in unschooled adults

Phonological and metaphonological skills are explored in 97 Brazilian illiterate and semiliterate adults. A simple letter- and word-reading task was used to define the degree of illiteracy. Phonemic awareness was strongly dependent on the level of letter and word reading ability. Phonological memory was very low in illiterates and unrelated to letter knowledge. Rhyme identification was relatively preserved in illiterates and semiliterates, and unrelated to letter and word reading level. Phonetic discrimination (minimal pairs) was fairly good and marginally related to reading ability. These results suggest that phonological sensitivity, phonological memory, rhyme identification, and phonemic awareness are distinctive cognitive processes, and that only phonemic awareness is clearly and strongly dependent on the alphabetical acquisition.     

Building permanent memory codes: codification and repetition effects in word identification

The studies presented in this article investigate the memory processes that underlie two phenomena in threshold identification: word superiority over pseudowords and the repetition effect (a prior presentation of an item facilitates later identification of that item). Codification (i.e., the development of a single memory code that can be triggered even by fragmented input information) explains the faster and more accurate identification of words than pseudowords. Our studies trace the development and retention of such codes for repeated pseudowords and examine the growth and loss of the repetition effect for both pseudowords and words. After approximately five prior occurrences, words and pseudowords are identified equally accurately in two types of threshold identification tasks, suggesting codification has been completed for pseudowords. Although the initial word advantage disappears, the accuracy of identification still increases with repetitions. The facilitation caused by repetition is not affected much by spacing within a session, but drops from one day to the next, and after a delay of one year has disappeared (new and old words were identified equally well). These results suggest an episodic basis for the repetition effect. Most important, after one year, performance is equal for old pseudowords and new and old words: all these levels are superior to that for new pseudowords, suggesting that the learned codes for pseudowords are as strong and permanent as the codes for words. A model of identification is presented in which feedback from codes and episodic images in memory facilitates letter processing. An instantiation of the model accounts for the major features of the data.     

Phonologically mediated priming of preexisting and new associations in young and older adults

In 2 experiments, the authors investigated phonologically mediated priming of preexisting and new associations in word retrieval. Young and older adults completed paired word stems with the first word that came to mind. Priming of preexisting associations occurred when word-stem pairs containing homophones (e.g., beech-s____) showed more completions with the target (e.g., sand) relative to unrelated pairs (e.g., batch-s____), with more priming for subordinate than for dominant homophones. Priming occurred for new associations independent of dominance such that word-stem pairs containing homophones (e.g., beech-l____ and beach-l____) were completed with the same word (e.g., laugh) more often than unrelated pairs (e.g., beech-l____ and batch-l____). No age differences in phonologically mediated priming were found for either type of association, suggesting age equivalence in the use of bottom-up phonological connections.     

Letter processing in the visual system: different activation patterns for single letters and strings

One would expect that a lifetime of experience recognizing letters would have an important influence on the visual system. Surprisingly, there is limited evidence of a specific neural response to letters over visual control stimuli. We measured brain activation during a sequential matching task using isolated characters (Roman letters, digits, and Chinese characters) and strings of characters. We localized the visual word form area (VWFA) by contrasting the response to pseudowords against that for letter strings, but this region did not show any other sign of visual specialization for letters. In addition, a left fusiform area posterior to the VWFA was selective for letter strings, whereas a more anterior left fusiform region showed selectivity for single letters. The results of different analyses using both large regions of interest and inspections of individual patterns of response reveal a dissociation between selectivity for letter strings and selectivity for single letters. The results suggest that reading experience fine-tunes visual representations at different levels of processing. An important conclusion is that the processing of nonpronounceable letter strings cannot be assumed to be equivalent to single-letter perception.