A letter visual-similarity matrix for Latin-based alphabets

Abstract

Indicators of letter visual similarity have been used for controlling the design of empirical and neuropsychological studies and for rigorously determining the factors that underlie reading ability and literacy acquisition. Additionally, these letter similarity/confusability matrices have been useful for studies examining more general aspects of human cognition, such as perception. Despite many letter visual-similarity matrices being available, they all have two serious limitations if they are to be used by researchers in the reading domain: (1) They have been constructed using atypical reading data obtained from speeded reading-aloud tasks and/or under degraded presentation conditions; (2) they only include letters from the English alphabet. Although some letter visual-similarity matrices have been constructed using data gathered from normal reading conditions, these either are based on old fonts, which may not resemble the letters found in modern print, or were never published. For the first time, this article presents a comprehensive letter visual-similarity/confusability matrix that has been constructed based on untimed responses to clearly presented upper-and lowercase letters that are present in many languages that use Latin-based alphabets, including Catalan, Dutch, English, French, Galician, German, Italian, Portuguese, and Spanish. Such a matrix will be useful for researchers interested in the processes underpinning reading and literacy acquisition.Keywords Letter visual-similarity/confusability matrix . Latin alphabets . Reading . Literacy acquisitionIn an extensive review of the literature spanning over 120 years, Mueller and Weidemann (2012) identified more than 70 published articles that had in one way or another sought to measure letter similarity (or confusability). From this review, the authors identified three main motivations for studying letter similarity: (1) practical attempts to make written text more comprehensible, and thereby allow learners to acquire reading skill more easily; (2) empirical investigations with the goal of understanding how the visual system functions; and (3) theoretical research attempting to explain how letters are represented by the visual system or, in abstract form, by the cognitive system. Regardless of the motivations for studying letter similarity, in the majority of these studies the same basic paradigm has been used-that of presenting single letters to participants, with the task being to name the presented item. A confusion matrix is then constructed by noting how often each letter was (incorrectly) given as a response to the presented letter. The number of responses given for each stimulus-response letter pair has been assumed to be an indication of the level of similarity (or confusability) between the two letters, with more errors on a pair indicating higher similarity/confusability. One problem with this paradigm is that if the letters are presented in a visually clear manner and no time limit to make a response is imposed on the participants, fe...

BACS: The Brussels Artificial Character Sets for studies in cognitive psychology and neuroscience

“…The results are highly similar for lowerand uppercase characters, for BACS-1 and BACS-2, and for the versions with and without serifs. Critically, the distributions are also very close to those computed for the Latin alphabet (data from Simpson et al, 2013), despite the use of a slightly different design (discrete scale, from 1 to 7) ( Fig. 12A and B).…”

“…11). Simpson et al (2013) Distribution plots show that the estimates are not uniformly distributed (Fig. 12C, D, E, F, G, H).…”

“…Among the different methods to measure letter similarity (e.g., Bagnara, Boles, Simion, & Umiltà, 1983;Boles & Clifford, 1989;Mueller & Weidemann, 2012), we used a similarity judgment task on a rating scale (e.g., Podgorny & Garner, 1979;Simpson, Mousikou, Montoya, & Defior, 2013). In this task, two characters are presented and participants have to assess how similar/dissimilar they are.…”

“…This was taken into account in BACS-1 and BACS-2. Furthermore, we provide objective measures of similarity (i.e., similarity matrices and clustering; Mueller & Weidemann, 2012;Podgorny & Garner, 1979;Simpson et al, 2013) so that researchers can easily select more similar or less similar characters.…”

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

“…Each target word was briefly preceded by (a) a lowercase identity prime; (b) a visually similar substituted-letter prime; or (c) a visually dissimilar substituted-letter prime. In Experiment 1, we used two critical letters (u and v) that had a high degree of estimated visual similarity: 4.93 in a 7-point Likert scale (Simpson, Mousikou, Montoya, & Defior, 2012) (e.g., neutral-NEUTRAL vs. nevtral-NEUTRAL vs. neztral-NEUTRAL). Experiment 2 was designed to replicate Experiment 1 with a different set of words; furthermore, the critical letters (i and j) had an even greater degree of visual similarity (5.17 out of 7; Simpson et al, 2012).…”