title: The effects of crowding on eye movement patterns in reading.
abstract: Crowding is a phenomenon that characterizes normal periphery limiting letter identification when other letters surround the signal. We investigated the nature of the reading limitation of crowding by analyzing eye-movement patterns. The stimuli consisted of two items varying across trials for letter spacing (spaced, unspaced and increased size), lexicality (words or pseudowords), number of letters (4, 6, 8), and reading modality (oral and silent). In Experiments 1 and 2 (oral and silent reading, respectively) the results show that an increase in letter spacing induced an increase in the number of fixations and in gaze duration, but a reduction in the first fixation duration. More importantly, increasing letter size (Experiment 3) produced the same first fixation duration advantage as empty spacing, indicating that, as predicted by crowding, only center-to-center letter distance, and not spacing per se, matters. Moreover, when the letter size was enlarged the number of fixations did not increase as much as in the previous experiments, suggesting that this measure depends on visual acuity rather than on crowding. Finally, gaze duration, a measure of word recognition, did not change with the letter size enlargement. No qualitative differences were found between oral and silent reading experiments (1 and 2), indicating that the articulatory process did not influence the outcome. Finally, a facilitatory effect of lexicality was found in all conditions, indicating an interaction between perceptual and lexical processing. Overall, our results indicate that crowding influences normal word reading by means of an increase in first fixation duration, a measure of word encoding, which we interpret as a modulatory effect of attention on critical spacing.
authors.affiliation: Psychology Department, University of Milano-Bicocca, Milano, Italy; Milan Center for Neuroscience, Milan, Italy. Electronic address: emanuela.bricolo@unimib.it.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Bricolo
authors.affiliation: Psychology Department, University of Milano-Bicocca, Milano, Italy.
authors.forename: Carola
authors.initials: C
authors.lastname: Salvi
authors.affiliation: Psychology Department, University of Rome "La Sapienza", Rome, Italy; IRCCS Fondazione Santa Lucia, Rome, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Martelli
authors.affiliation: Department of Human Sciences, University LUMSA, Rome, Italy; Institute of Cognitive Sciences and Technologies, ISTC-CNR, Rome, Italy.
authors.forename: Lisa S
authors.initials: LS
authors.lastname: Arduino
authors.affiliation: Psychology Department, University of Milano-Bicocca, Milano, Italy; Milan Center for Neuroscience, Milan, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Daini
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011932:Reading; D055815:Young Adult
keywords: Crowding; Eye movements; Reading; Space