Visual similarity effects on masked priming

Parafoveal letter identification in Russian: Confusion matrices based on error rates

In the present study, we introduce parafoveal letter confusion matrices for the Russian language, which uses the Cyrillic script. To ensure that our confusion rates reflect parafoveal processing and no other effects, we employed an adapted boundary paradigm (Rayner, 1975) that prevented the participants from directly fixating the letter stimuli. Additionally, we assessed confusability under isolated and word-like (crowded) conditions using two modern fonts, since previous research showed that letter recognition depended on crowding and font (Coates, 2015; Pelli et al., 2006). Our additional goal was to gain insight into what letter features or configurational patterns might be essential for letter recognition in Russian; thus, we conducted exploratory clustering analysis on visual confusion scores to identify groups of similar letters. To support this analysis, we conducted a comprehensive review of over 20 studies that proposed crucial properties of Latin letters relevant to character perception. The summary of this review is valuable not only for our current study but also for future research in the field.

On the distinction between position and order information when processing strings of characters

To probe the processing of gaze-dependent positional information and gaze-independent order information when matching strings of characters, we compared effects of visual similarity (hypothesized to affect gaze-centered position coding) with the effects of character transpositions (hypothesized to affect the processing of gaze-independent order information). In Experiment 1, we obtained empirical measures of visual similarity for pairs of characters, separately for uppercase consonants and keyboard symbols. These similarity values were then used in Experiment 2 to create pairs of four-character stimuli (four letters or four symbols) that could differ by substituting one character with a different character from the same category that was visually similar (e.g., FJDK-FJBK) or dissimilar (e.g., FJVK-FJBK). We also compared the effects of transposing two characters (e.g., FBJK-FJBK) with substituting two characters (e.g., FHSK-FJBK). "Different" responses were harder to make in the single substitution condition when the substituted character was visually similar, and this effect was not conditioned by character type. On the other hand, transposition costs (i.e., greater difficulty in detecting a difference with transpositions compared with double substitutions) were greater for letters compared with symbols. We conclude that visual similarity mainly affects the generic gaze-dependent processing of complex visual features, and that the encoding of letter order involves a mechanism that is specific to reading.

EXPRESS: Orthographic and feature-level contributions to letter identification

Word recognition is facilitated by primes containing visually similar letters (dentjst-dentist, Marcet & Perea, 2017), suggesting that letter identities are encoded with initial uncertainty. Orthographic knowledge also guides letter identification, as readers are more accurate at identifying letters in words compared to pseudowords (Reicher, 1969; Wheeler, 1970). We investigated how higher-level orthographic knowledge and low-level visual feature analysis operate in combination during letter identification. We conducted a Reicher-Wheeler task to compare readers' ability to discriminate between visually similar and dissimilar letters across different orthographic contexts (words, pseudowords, and consonant strings). Orthographic context and visual similarity had independent effects on letter identification, and there was no interaction between these factors. The magnitude of these effects indicated that higher-level orthographic information plays a greater role than lower-level visual feature information in letter identification. We propose that readers use orthographic knowledge to refine potential letter candidates while visual feature information is accumulated. This combination of higher-level knowledge and low-level feature analysis may be essential in permitting the flexibility required to identify visual variations of the same letter (e.g. N-n) whilst maintaining enough precision to tell visually similar letters apart (e.g. n-h). These results provide new insights on the integration of visual and linguistic information and highlight the need for greater integration between models of reading and visual processing. This study was pre-registered on the Open Science Framework. Pre-registration, stimuli, instructions, trial-level data, and analysis scripts are openly available (https://osf.io/p4q9u/).

Letter identity and visual similarity in the processing of diacritic letters

Are letters with a diacritic (e.g., â) recognized as a variant of the base letter (e.g., a), or as a separate letter identity? Two recent masked priming studies, one in French and one in Spanish, investigated this question, concluding that this depends on the language-specific linguistic function served by the diacritic. Experiment 1 tested this linguistic function hypothesis using Japanese kana, in which diacritics signal consonant voicing, and like French and unlike Spanish, provide lexical contrast. Contrary to the hypothesis, Japanese kana yielded the pattern of diacritic priming like Spanish. Specifically, for a target kana with a diacritic (e.g., ガ, /ga/), the kana prime without the diacritic (e.g., カ, /ka/) facilitated recognition almost as much as the identity prime (e.g., ガ-ガ = カ-ガ), whereas for a target kana without a diacritic, the kana prime with the diacritic produced less facilitation than the identity prime (e.g., カ-カ < ガ-カ). We suggest that the pattern of diacritic priming has little to do with linguistic function, and instead it stems from a general property of visual object recognition. Experiment 2 tested this hypothesis using visually similar letters of the Latin alphabet that differ in the presence/absence of a visual feature (e.g., O and Q). The same asymmetry in priming was observed. These findings are consistent with the noisy channel model of letter/word recognition (Norris & Kinoshita, Psychological Review, 119, 517-545, 2012a).

Serial and syntactic processing in the visual analysis of multi-digit numbers

The visual analysis of letter strings and digit strings is done by two separate cognitive processes. Recent studies have hypothesized that these processes are not only separate but also qualitatively different, in that they may encode information specific to numbers or to words. To examine this hypothesis and to shed further light on the visual analysis of numbers, we asked adults to read aloud multi-digit strings presented to them for brief durations. Their performance was better in digits on the number's left side than in digits farther to the right, with better performance in the two outer digits than their neighbors. This indicates the digits were processed serially, from left to right. Visual similarity of digits increased the likelihood of errors, and when a digit migrated to an incorrect position, it was most often to an adjacent location. Interestingly, the positions of 0 and 1 were encoded better than the positions of 2-9, and 2-9 were identified better when they were next to 0 or 1. To accommodate these findings, we propose a detailed model for the visual analysis of digit strings. The model assumes imperfect digit detectors in which a digit's visual information leaks to adjacent locations, and a compensation mechanism that inhibits this leakage. Crucially, the compensating inhibition is stronger for 0 and 1 than for the digits 2-9, presumably because of the importance of 0 and 1 in the number system. This sensitivity to 0 and 1 makes the visual analyzer specifically adapted to numbers, not words, and may be one of the brain's reasons to implement the visual analysis of numbers and words in two separate cognitive processes.

The role of letter features on the consonant-bias effect: Evidence from masked priming

Recent research has shown an advantage of consonants at early stages of visual word recognition (C-bias), although the locus of this effect remains elusive. Here we examine whether the C-bias is affected by the consonant letters' features. Skilled readers performed a masked priming lexical decision task in which target words containing only either consonants without any ascending/descending features (flat words, canino[canine]) or consonants with ascending/descending features (non-flat words, palito[toothpick]) were preceded by briefly (50 ms) presented primes that could preserve the same consonants of the targets (cenune-CANINO, pelute-PALITO), the same vowels of the targets (raxizo-CANINO, fajibo-PALITO), or, as controls, unrelated (ruxuze-CANINO, fejube-PALITO) and identity primes (canino-CANINO, palito-PALITO). The case in which prime-target pairs were presented was also manipulated (lower-upper vs. upper-lower). Results showed that in both case conditions flat words were recognized faster than non-flat words. Evidence for the C-bias was observed both for flat and non-flat words in the lower-upper condition, in which a vowel inhibitory priming effect was also observed for non-flat words. In the upper-lower condition, however, the C-bias was restricted to flat words. These findings suggest that letter features play a role in the C-bias and ask for amendments in current models of visual word recognition.

Does a mark make a difference? Visual similarity effects with accented vowels

Visual similarity effects are pervasive in masked priming (e.g., T4BLE→TABLE; obiect→OBJECT; docurnent→DOCUMENT) and can be easily explained in terms of uncertainty regarding letter identity. However, recent research failed to show visual similarity effects for primes containing accented vowels (e.g., féliz-FELIZ behaves as fáliz-FELIZ [happy in Spanish]). This null effect has been taken to suggest that accented and non-accented vowels (e.g., é and e) activate completely distinct representations. However, priming effects are reinstated for non-accented vowels (e.g., facil-FÁCIL < fecil-FÁCIL [easy in Spanish]). Here we tested the hypothesis that the lack of priming effects for primes containing accented vowels is a simple consequence of the saliency of the accent marks. To investigate this issue, we conducted a masked priming lexical decision experiment in which we minimized the saliency of the diacritical marks by using primes containing the letter i (i.e., a letter that contains itself a glyph over the letter). We manipulated prime-target visual similarity and the presence/absence of an accented vowel in the prime (e.g., obieto-OBJETO vs. obaeto-OBJETO; obíeto-OBJETO vs. obáeto-OBJETO [object in Spanish]). Results showed a sizeable visual similarity effect regardless of whether the prime was accented or not. Therefore, these findings suggest that, at least in scripts like Spanish, there is nothing special about the processing of accented vs. unaccented vowels once the saliency of the diacritical marks is reduced.

When does rotation disrupt letter encoding? Testing the resilience of letter detectors in the initial moments of processing

Previous research has reported that both letter and word identification are slower when the stimuli are presented at rotations above 45° than when presented in their canonical horizontal view. Indeed, influential models of word recognition posit that letter detectors in the visual word recognition system are disrupted by rotation angles above 40° or 45° (e.g., Local Combinations Detector model; Dehaene, Cohen, Sigman, & Vinckier, 2005, Trends in Cognitive Sciences). However, recent experiments have shown robust masked identity/form priming effects for 90° rotated words, thus calling into question this assumption. Here we aimed to isolate the degree to which letter detectors are disrupted when manipulating letter rotation in three masked identity priming letter match experiments. Probes and targets were always presented in the canonical upright position, whereas forwardly masked primes were rotated in different angles. The rotation angles were 0° versus 45° (Experiment 1), 22.5° versus 67.5° (Experiment 2), and 45° versus 90° (Experiment 3). Results showed a sizeable masked identity priming effect regardless of the rotation angle, hence demonstrating that letter detectors are not disrupted by rotations smaller than 90° in the early moments of letter processing. This pattern suggests that letter detectors are more resilient to changes in visual form than predicted by the LCD model.

Is nevtral NEUTRAL? Visual similarity effects in the early phases of written-word recognition

For simplicity, contemporary models of written-word recognition and reading have unspecified feature/letter levels-they predict that the visually similar substituted-letter nonword PEQPLE is as effective at activating the word PEOPLE as the visually dissimilar substituted-letter nonword PEYPLE. Previous empirical evidence on the effects of visual similarly across letters during written-word recognition is scarce and nonconclusive. To examine whether visual similarity across letters plays a role early in word processing, we conducted two masked priming lexical decision experiments (stimulus-onset asynchrony = 50 ms). The substituted-letter primes were visually very similar to the target letters (u/v in Experiment 1 and i/j in Experiment 2; e.g., nevtral-NEUTRAL). For comparison purposes, we included an identity prime condition (neutral-NEUTRAL) and a dissimilar-letter prime condition (neztral-NEUTRAL). Results showed that the similar-letter prime condition produced faster word identification times than the dissimilar-letter prime condition. We discuss how models of written-word recognition should be amended to capture visual similarity effects across letters.

Do Diacritical Marks Play a Role at the Early Stages of Word Recognition in Arabic?

A crucial question in the domain of visual word recognition is whether letter similarity plays a role in the early stages of visual word processing. Here we focused on Arabic because in this language there are various groups of letters that share the same basic shape and only differ in the number/location of diacritical points. We conducted a masked priming lexical decision experiment in which a target word was preceded by: (i) an identity prime; (ii) a prime in which the critical letter was replaced by a letter with the same shape that differed in the number of diacritics (e.g., ); or (iii) a prime in which the critical letter was replaced by a letter with different shape (e.g., ). Results showed a sizable advantage of the identity condition over the two substituted-letter priming conditions (i.e., diacritical information is rapidly processed). Thus, diacritical marks play an essential role in the “feature letter” level of models of visual word recognition in Arabic.

Context-dependent similarity effects in letter recognition

In visual word recognition tasks, digit primes that are visually similar to letter string targets (e.g., 4/A, 8/B) are known to facilitate letter identification relative to visually dissimilar digits (e.g., 6/A, 7/B); in contrast, with letter primes, visual similarity effects have been elusive. In the present study we show that the visual similarity effect with letter primes can be made to come and go, depending on whether it is necessary to discriminate between visually similar letters. The results support a Bayesian view which regards letter recognition not as a passive activation process driven by the fixed stimulus properties, but as a dynamic evidence accumulation process for a decision that is guided by the task context.