title: The effect of hand movements on numerical bisection judgments in early blind and sighted individuals.
abstract: Recent evidence suggests that in representing numbers blind individuals might be affected differently by proprioceptive cues (e.g., hand positions, head turns) than are sighted individuals. In this study, we asked a group of early blind and sighted individuals to perform a numerical bisection task while executing hand movements in left or right peripersonal space and with either hand. We found that in bisecting ascending numerical intervals, the hemi-space in which the hand was moved (but not the moved hand itself) influenced the bisection bias similarly in both early blind and sighted participants. However, when numerical intervals were presented in descending order, the moved hand (and not the hemi-space in which it was moved) affected the bisection bias in all participants. Overall, our data show that the operation to be performed on the mental number line affects the activated spatial reference frame, regardless of participants' previous visual experience. In particular, both sighted and early blind individuals' representation of numerical magnitude is mainly rooted in world-centered coordinates when numerical information is given in canonical orientation (i.e., from small to large), whereas hand-centered coordinates become more relevant when the scanning of the mental number line proceeds in non-canonical direction.
authors.affiliation: Department of Psychology, University of Milano-Bicocca, Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Rinaldi
authors.affiliation: Brain Connectivity Center, C. Mondino National Neurological Institute, Pavia, Italy; Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.
authors.forename: Tomaso
authors.initials: T
authors.lastname: Vecchi
authors.affiliation: Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.
authors.forename: Micaela
authors.initials: M
authors.lastname: Fantino
authors.affiliation: The Laboratory for Visual Neuroplasticity, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, USA.
authors.forename: Lotfi B
authors.initials: LB
authors.lastname: Merabet
authors.affiliation: Department of Psychology, University of Milano-Bicocca, Milano, Italy; Brain Connectivity Center, C. Mondino National Neurological Institute, Pavia, Italy. Electronic address: zaira.cattaneo@unimib.it.
authors.forename: Zaira
authors.initials: Z
authors.lastname: Cattaneo
mesh_terms: D000328:Adult; D001766:Blindness / Q000523:psychology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006225:Hand; D006801:Humans; D007600:Judgment; D008297:Male; D008875:Middle Aged; D009068:Movement; D010812:Physical Stimulation; D013028:Space Perception; D014785:Vision, Ocular / Q000502:physiology*; D014796:Visual Perception; D019987:Persons with Visual Disabilities
keywords: Blindness; Hand movements; Lateralization; Number bisection; Number line; Pseudoneglect