Previous studies have shown differential responses in the fusiform and lingual gyri during reading and suggested that the former is engaged in processing local features of visual stimuli and the latter is engaged in global shape processing. We used positron emission tomography in order to investigate how these regions are modulated by two common variables in reading: word length (three, six and nine letters) and perceptive similarity to the background (high and low contrast). Increasing both word length and visual contrast had a positive monotonic effect on activation in the bilateral fusiform. However, in the lingual gyrus, activation increased with increasing word length but decreased with increasing contrast. On the basis of previous studies, we suggest that (i) increasing word length increases the demands on both local feature and global shape processing, but (ii) increasing visual contrast increases the demands on local feature processing while decreasing the demands on global shape processing.

MiXeD-cAsE stimuli have long been used to test whether word recognition is based on holistic visual information or preliminary letter identification. However, without knowing which properties of mixed-case stimuli disrupt processing, it is not possible to determine which visual units mediate word recognition. The present studies examined the effects of case mixing on word and nonword naming as a function of (a) whether spaces were inserted between letters and (b) whether letter size was alternated independent of letter case. The results suggest that case-mixing disruption effects are due to at least 2 factors: the introduction of inappropriate grouping between letters with the same size and case, and the disruption of transletter features. The data support a model of visual lexical access based on the input from multiple visually based units.

MiXeD-cAsE stimuli are often used in reading research to investigate which characteristics of a word's visual form are important to its speed of processing. In this article, the effect of case mixing on a variety of lexical tasks was examined. Lexical decision was found to be more disrupted by case mixing than was word naming or semantic categorization. However, where word naming was shown to be purely lexical, it too was affected to a greater extent than categorization. Case mixing and word frequency interacted in sub lexical naming but were additive in lexical naming, lexical decision, and semantic categorization. Case mixing did not interact with spelling-to-sound regularity or eradicate homophone and pseudohomophone effects. It is concluded that case mixing disrupts both early letter coding and a familiarity check mechanism (D. Besner & R. S. McCann, 1987). Semantic and syntactic processing continues normally following the disrupted production of abstract letter codes.

The early stages of visual word recognition were investigated by scanning participants using PET as they took part in implicit and explicit reading tasks with visually disrupted stimuli. CaSe MiXiNg has been shown in behavioral studies to increase reaction times (RTs) in naming and other word recognition tasks. In this study, we found that during both an implicit (feature detection) task and an explicit word-naming task, mixed-case words compared to same-case words produced increased activation in an area of the right parietal cortex previously associated with visual attention. No effect of case was found in this area for pseudowords or consonant strings. Further, lowering the contrast of the stimuli slowed RTs as much as case mixing, but did not lead to the same increase in right parietal activation. No significant effect of case mixing was observed in left-hemisphere language areas. The results suggest that reading mixed-case words requires increased attentional processing. However, later word recognition processes may be relatively unaffected by the disruption in presentation.

This study investigates the relative roles of internal and external letter features in word recognition. In Experiment 1 the efficacy of outer word fragments (words with all their horizontal internal features removed) was compared with inner word fragments (words with their outer features removed) as primes in a forward masking paradigm. These forward masked primes were followed by a word to be read aloud. Outer word primes presented for longer durations produced significantly faster naming responses than inner primes. Outer parts of words appear to provide more relevant information for lexical access at an earlier stage than inner fragments. In Experiment 2 words with only external features were named correctly on 96% of occasions compared with 52% of words with only their inner features presented. This indicates much greater information content in the periphery of a word (despite having a reduced area of print available: 45% compared to 55%). Multiple regression analyses controlling for 'guessability' (from data in Experiment 2) still produced significantly faster reaction times in the outer relative to the inner priming condition for longer prime durations. These experiments demonstrate that first, the most informative letter features are concentrated in the peripheral region of words; and second, even controlling for this effect, readers appear to have a bias towards analysing outer features of a word before inner features.An enduring and unresolved issue in visual word recognition research has been the role of a word's outline shape in lexical access (e.g. Cattell, 1886;Haber, Haber & Furlin, 1983). An efficient and rapidly operating word recognition system might be expected to develop simplifying procedures that initially identify letter features on the outer edges of words, as the ascending, descending and neutral letters of words often produce unique configurations of salient features. One issue is whether it is the envelope (or the external contour) surrounding a word or the features on the periphery (e.g. the dot in the letter i) that are important. As will be seen, current evidence appears to be against the word envelope hypothesis, but not necessarily against the notion that the salient external features are important.Previous studies that have examined the role of word shape in lexical access have had mixed results. Haber, Haber and Furlin (1983) used a cloze paradigm, in which students