When parallel processing in visual word recognition is not enough: new evidence from naming

Low-frequency irregular words are named more slowly and are more error prone than low-frequency regular words (the regularity effect). Rastle and Coltheart (1999) reported that this irregularity cost is modulated by the serial position of the irregular grapheme-phoneme correspondence, such that words with early irregularities exhibit a larger cost than words with late ones. They argued that these data implicate rule-based serial processing, and they also reported a successful simulation with a model that has a rule-based serial component—the DRC model of reading aloud (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001). However, Zorzi (2000) also simulated these data with a model that operates solely in parallel. Furthermore, Kwantes and Mewhort (1999) simulated these data with a serial processing model that has no rules for converting orthography to phonology. The human data reported by Rastle and Coltheart therefore neither require a serial processing account, nor successfully discriminate among a number of computational models of reading aloud. New data are presented wherein an interaction between the effects of regularity and serial position of irregularity is again reported for human readers. The DRC model simulated this interaction; no other implemented computational model does so. The present results are thus consistent with rule-based serial processing in reading aloud.     

Can the dual-route cascaded computational model of reading offer a valid account of the masked onset priming effect?

The masked onset priming effect (MOPE) refers to the empirical finding that target naming is faster when the target (SIB) is preceded by a briefly presented masked prime that starts with the same letter/phoneme (suf) than when it does not (mof; Kinoshita, 2000, Experiment 1). The dual-route cascaded (DRC) computational model of reading (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) has offered an explanation for how the MOPE might occur in humans. However, there has been some empirical discrepancy regarding whether for nonword items the effect is limited to the first-letter/phoneme overlap between primes and targets or whether orthographic/phonological priming effects occur beyond the first letter/phoneme. Experiment 1 tested these two possibilities. The human results, which were successfully simulated by the DRC model, showed priming beyond the first letter/phoneme. Nevertheless, two recent versions of the DRC model made different predictions regarding the nature of these priming effects. Experiment 2 examined whether it is facilitatory, inhibitory, or both, in order to adjudicate between the two versions of the model. The human results showed that primes exert both facilitatory and inhibitory effects.     

Neighbourhood density effects in reading aloud: new insights from simulations with the DRC model.

A series of nine simulations with the Dual Route Cascaded (DRC) model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) investigated neighbourhood density (N) effects in nonword and word naming. Two main finding emerged from this work. First, when naming nonwords there are two loci for the effect of N in the model, contrary to Coltheart et al.'s single locus explanation of what the model is doing. The early N effect involves interactive activation between the orthographic lexicon and the letter units such that high N facilitates letter identification, which in turn affects the nonlexical route. The late N effect arises from activation in the orthographic lexicon that feeds forward to the phonological lexicon and primes phonemes in the phoneme system. Second, when naming words the presence/absence of an effect of N on the Letter Units through feedback from the lexical level depends on the parameter settings. Implications and suggestions for future directions are made.     

Neighbourhood density, word frequency, and spelling-sound regularity effects in naming: similarities and differences between skilled readers and the Dual Route Cascaded Computational model.

An experiment with skilled readers and a series of simulations with the Dual Route Cascaded model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) investigated the joint effects of stimulus quality and Neighbourhood Density (N) in nonword naming. Neighbourhood Density and stimulus quality yielded additive effects on RT for skilled readers whereas the model produced an interaction between these factors. A further set of simulations show that DRC also produces an interaction between stimulus quality and (1) word frequency, (2) spelling-sound regularity, and, (3) nonword letter length. None of these three factors interact with stimulus quality in performance by skilled readers. It is suggested that DRC's assumption of cascaded processing throughout represents a central problem. A proposal as to how the model can be modified to accommodate these and other problematic data is discussed.     

Reading aloud polysyllabic words and nonwords: The syllabic length effect reexamined

Two experiments were run in order to reinvestigate the role of the number of syllables in naming. Experiment 1 (word naming) showed that effects of number of syllables on naming latency were observed for very low-frequency words but not for high-frequency words (thus replicating Jared & Seidenberg’s, 1990, finding). In Experiment 2 (nonword naming), syllabic length effects were also obtained for nonwords. Control experiments found no effect on the latency of delayed naming of the same words and nonwords. These results suggest that naming does require syllabic decomposition, at least for very low-frequency words and nonwords in French. In particular, these data are compatible with any model of reading that postulates that reading aloud depends on the activity of two procedures: (1) a procedure that operates in parallel across a letter string (and does not generate a strong syllabic length effect) and that is the predominant process in generating responses to high-frequency words, and (2) another procedure that operates serially across a letter string (and generates a strong syllabic length effect) and that is the predominant process in generating responses to very low-frequency words and nonwords. These results are discussed in the context of the multiple-trace memory model for polysyllabic word naming (Ans, Carbonnel, & Valdois, 1998).     

Zeading and reazing: which is faster? The position of the diverging letter in a pseudoword determines reading time

We present evidence that (a) at least some components of the reading process are serial and (b) pseudoword reading is affected by lexical knowledge, even in a transparent orthographic system like Italian. Pseudowords deriving from five-letter words by changing either the first or the fourth letter were presented for reading aloud. Results showed an effect of the position of the diverging letter: Early diverging pseudowords were read more slowly than late diverging pseudowords. The dual-route cascaded (DRC) model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) successfully simulated the behavioural data.     

Zeading and reazing: Which is faster? The position of the diverging letter in a pseudoword determines reading time

We present evidence that (a) at least some components of the reading process are serial and (b) pseudoword reading is affected by lexical knowledge, even in a transparent orthographic system like Italian. Pseudowords deriving from five-letter words by changing either the first or the fourth letter were presented for reading aloud. Results showed an effect of the position of the diverging letter: Early diverging pseudowords were read more slowly than late diverging pseudowords. The dual-route cascaded (DRC) model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001 Coltheart, M., Rastle, K., Perry, C., Langdon, R. and Ziegler, J. 2001. DRC: A dual route cascaded model of visual word recognition and reading aloud. Psychological Review, 108: 204–256. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) successfully simulated the behavioural data.     

The DRC model of visual word recognition and reading aloud: An extension to German

The dual-route cascaded (DRC) model of word recognition and reading aloud was implemented in German. In this paper, we describe crosslinguistic differences and similarities between the German and the English DRC. The German DRC was evaluated with respect to its ability to correctly pronounce all German monosyllabic words and to simulate the loan word (regularity) effect. Furthermore, we obtained DRC predictions concerning a number of benchmark effects previously investigated in English, namely effects of word frequency, word length, and neighbourhood size.     

The effect of oral vocabulary on reading visually novel words: a comparison of the dual-route-cascaded and triangle frameworks

Dual-route-cascaded (DRC) (e.g. Coltheart & Rastle, Journal of Experimental Psychology: Human Perception and Performance 20 (1994) 1197) and triangle framework (e.g. Seidenberg & McClelland, Psychological Review 96 (1989) 523) predictions were tested regarding the effect of having a word in oral vocabulary prior to reading that same word. Over two sessions, at intervals of 2--3 days, 44 Grade 1 (6--7-year-old) children were aurally familiarized with the sound and meaning of ten novel words (semantic oral instantiation), and with just the sound of another ten novel words (non-semantic oral instantiation). Two to three days later non-word naming performance was significantly more accurate for aurally trained novel words compared to pseudohomophones, which were in turn advantaged over untrained non-words. The semantic manipulation had no effect. Experiment 2 manipulated articulation during (non-semantic) training. Forty Grade 1 children participated. Again, aurally trained items were named more accurately and quickly than equivalently trained pseudohomophones, which were in turn advantaged over untrained non-words. The articulation manipulation had no effect. The results suggest that word-specific phonological information is represented in the reading system independently of semantic or articulatory influences. The results are interpreted as being problematic for both the DRC and triangle frameworks, but more so for the latter.     

Masked phonological priming effects in English: are they real? Do they matter?

For over 15 years, masked phonological priming effects have been offered as evidence that phonology plays a leading role in visual word recognition. The existence of these effects-along with their theoretical implications-has, however, been disputed. The authors present three sources of evidence relevant to an assessment of the existence and implications of these effects. First, they present an exhaustive meta-analytic literature review, in which they evaluate the strength of the evidence for masked phonological priming effects on English visual word processing. Second, they present two original experiments that demonstrate a small but significant masked priming effect on English visual lexical decision, which persists in conditions that may discourage phonological recoding. Finally, they assess the theory of visual word recognition offered by the DRC model (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001) in the context of their empirical data. Through numerous simulations with this model, they argue that masked phonological priming effects might best be captured by a weak phonological (i.e., dual-access) theory in which lexical decisions are made on the basis of phonological information.     

A position-sensitive Stroop effect: further evidence for a left-to-right component in print-to-speech conversion

In the classical Stroop effect, response times for naming the color in which a word is printed are affected by the presence of semantic, phonological, or orthographic relationships between the stimulus word and the response word. We show that color naming responses are faster when the printed word shares a phoneme with the color name to be produced than when it does not, in conditions where there is no semantic relationship between the printed word and the color name. This result is compatible with a variety of computational models of reading. However, we also found that these effects are much larger when it is the first phoneme that the stimulus and response share than when it is the last. Our data are incompatible with computational models of reading in which the computation of phonology from print is purely parallel. The dual route cascaded model computational model of reading, which has a lexical route that operates in parallel and a nonlexical route that operates serially letter by letter, successfully simulates this position-sensitive Stroop effect. The model also successfully simulates the “onset effect” in masked priming (Forster & Davis, 1991) and the interaction between the regularity effect and the position in a word of a grapheme-phoneme irregularity (Rastle & Coltheart, 1999b)-effects which, we argue, arise for the same reason as the position-sensitive Stroop effect we report.     

Cross-language computational investigation of the length effect in reading aloud

The authors examined whether 2 computational models of reading, the dual-route cascaded model (M. Coltheart, K. Rastle, C. Perry, R. Langdon, & J. C. Ziegler, 2001) and the connectionist 2-layer model (M. Zorzi, G. Houghton, & B. Butterworth, 1998), were able to predict the pattern that the length effect found in reading aloud is larger in German than in English (J. C. Ziegler, C. Perry, A. M. Jacobs, & M. Braun, 2001). The results showed that the dual-route cascaded model, which uses a serial mechanism for assembling phonology, successfully predicted this cross-language difference. In contrast, the connectionist model of Zorzi et al. (1998) predicted the opposite: a larger length effect in English than in German. Both the success of one model and the failure of the other highlight fundamental differences between 2 major classes of computational models.     

Reading nonwords aloud: Results requiring change in the dual route cascaded model

The time to name a nonword increases monotonically as letter length increases. The leading computational model of basic processes in reading (Coltheart, Rastle, Perry, Langdon & Ziegler's dual route cascaded model) simulates this, because its nonlexical route assigns phonemes to letters serially, left to right, and arguably, this corresponds to what humans do. New simulation work shows that (1) this letter length effect interacts with the effect of slowing the rate of early processing, and (2) the model produces a qualitatively different pattern from that observed with university-level readers. The contrast between simulation and human performance thus illuminates a problem with how the nonlexical route operates in the model, and constrains accounts that can be provided for the human data. Consideration is given to thresholding the output of the letter-level module as a way to modify the model so as to make it possible to simulate the human data.     

A Computational Model of the Self‐Teaching Hypothesis Based on the Dual‐Route Cascaded Model of Reading

The self‐teaching hypothesis describes how children progress toward skilled sight‐word reading. It proposes that children do this via phonological recoding with assistance from contextual cues, to identify the target pronunciation for a novel letter string, and in so doing create an opportunity to self‐teach new orthographic knowledge. We present a new computational implementation of self‐teaching within the dual‐route cascaded (DRC) model of reading aloud, and we explore how decoding and contextual cues can work together to enable accurate self‐teaching under a variety of circumstances. The new model (ST‐DRC) uses DRC’s sublexical route and the interactivity between the lexical and sublexical routes to simulate phonological recoding. Known spoken words are activated in response to novel printed words, triggering an opportunity for orthographic learning, which is the basis for skilled sight‐word reading. ST‐DRC also includes new computational mechanisms for simulating how contextual information aids word identification, and it demonstrates how partial decoding and ambiguous context interact to achieve irregular‐word learning. Beyond modeling orthographic learning and self‐teaching, ST‐DRC’s performance suggests new avenues for empirical research on how difficult word classes such as homographs and potentiophones are learned.     

The effect of orientation on number word processing

Besner and Coltheart [Besner, D., & Coltheart, M. (1979). Ideographic and alphabetic processing in skilled reading of English. Neuropsychologia, 17, 467-472] found a size congruity effect for Arabic numbers but not for number words. They proposed that Arabic numbers and number words are processed in different ways. However, in their study orientation of the stimuli and notation were confounded. In the present study, it is found that orientation of number words affects numerical processing. Orientation modulates both the size congruity effect and the distance effect; horizontal presentation produces similar results to those produced by Arabic numbers whereas vertical orientation produces different results. Accordingly, it is proposed that our cognitive system is endowed with two different mechanisms for numerical processing; one relies on a visual-spatial code and the other on a verbal code.     

"Serial" effects in parallel models of reading

There is now considerable evidence showing that the time to read a word out loud is influenced by an interaction between orthographic length and lexicality. Given that length effects are interpreted by advocates of dual-route models as evidence of serial processing this would seem to pose a serious challenge to models of single word reading which postulate a common parallel processing mechanism for reading both words and nonwords (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001; Rastle, Havelka, Wydell, Coltheart, & Besner, 2009). However, an alternative explanation of these data is that visual processes outside the scope of existing parallel models are responsible for generating the word-length related phenomena (Seidenberg & Plaut, 1998). Here we demonstrate that a parallel model of single word reading can account for the differential word-length effects found in the naming latencies of words and nonwords, provided that it includes a mapping from visual to orthographic representations, and that the nature of those orthographic representations are not preconstrained. The model can also simulate other supposedly "serial" effects. The overall findings were consistent with the view that visual processing contributes substantially to the word-length effects in normal reading and provided evidence to support the single-route theory which assumes words and nonwords are processed in parallel by a common mechanism.     

Serial processing in reading aloud: reply to Zorzi (2000)

K. Rastle and M. Coltheart (1999; see also M. Coltheart & K. Rastle, 1994) reported data demonstrating that the cost of irregularity in reading aloud low-frequency exception words is modulated by the position of the irregularity in the word. They argued that these data implicated a serial process and falsified all models of reading aloud that operate solely in parallel, a conclusion that M. Zorzi (2000) challenged by successfully simulating the position of irregularity effect with such a model. Zorzi (2000) further claimed that a reanalysis of K. Rastle and M. Coltheart's (1999) data demonstrates sensitivity to grapheme-phoneme consistency (which he claimed was confounded across the position of irregularity manipulation) rather than the use of a serial process. Here, the authors argue that M. Zorzi's (2000) reanalyses were inappropriate and reassert that K. Rastle and M. Coltheart's (1999) findings are evidence for serial processing.     

Predicting children's word‐spelling difficulty for common English words from measures of orthographic transparency,phonemic and graphemic length and word frequency

Spencer demonstrated that spelling and reading difficulty for English words can be predicted from a number of factors, including word frequency, phonemic length and measures of orthographic depth and complexity. In this study, spelling difficulty of high frequency words was investigated across five year groups (ages 7 to 11 years) with a wide ranging series of data sources from which to determine word frequency values and orthographic depth measures. A regression model accounted for 52–66% of the variance for 7‐ to 11‐year‐olds and 72% of the variance for the lowest performing quartile group, irrespective of age. The most influential factor, phonetic difference (being the difference in the number of letters and phonemes in a word, and representing grapheme complexity), links the relative influence of large graphemic units in foundation literacy to a similar phenomenon, the ‘whammy’ effect, which provides support for serial processing in the dual route cascade model of word recognition in skilled readers ( Rastle & Coltheart, 1998 ). The study supports recent research on European orthographies, which concludes that both orthographic depth and complexity contribute to delayed acquisition of foundation literacy skills.