title: Non-visual numerical discrimination in a blind cavefish (Phreatichthys andruzzii).
abstract: Over a decade of comparative studies, researchers have found that rudimentary numerical abilities are widespread among vertebrates. While experiments in mammals and birds have employed a variety of stimuli (visual, auditory and tactile), all fish studies involved visual stimuli and it is unknown whether fish can process numbers in other sensory modalities. To fill this gap, we studied numerical abilities in Phreatichthys andruzzii, a blind cave-dwelling species that evolved in the phreatic layer of the Somalia desert. Fish were trained to receive a food reward to discriminate between two groups of objects placed in opposite positions of their home tank. In Experiment 1, subjects learned to discriminate between two and six objects, with stimuli not controlled for non-numerical continuous variables that co-vary with numbers, such as total area occupied by stimuli or density. In Experiment 2, the discrimination was two versus four, with half of the stimuli controlled for continuous quantities and half not controlled for continuous quantities. The subjects discriminated only the latter condition, indicating that they spontaneously used non-numerical information, as other vertebrates tested in similar experiments. In Experiments 3 and 4, cavefish trained from the beginning only with stimuli controlled for continuous quantities proved able to learn the discrimination of quantities based on the sole numerical information. However, their numerical acuity was lower than that reported in other teleost fish tested with visual stimuli.
authors.affiliation: Department of General Psychology, University of Padova, 35131 Padova, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Bisazza
authors.affiliation: Department of General Psychology, University of Padova, 35131 Padova, Italy.
authors.forename: Christian
authors.initials: C
authors.lastname: Tagliapietra
authors.affiliation: Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Bertolucci
authors.affiliation: Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy.
authors.forename: Augusto
authors.initials: A
authors.lastname: Foà
authors.affiliation: Department of General Psychology, University of Padova, 35131 Padova, Italy christian.agrillo@unipd.it.
authors.forename: Christian
authors.initials: C
authors.lastname: Agrillo
mesh_terms: D000818:Animals; D003071:Cognition; D003216:Conditioning, Operant; D003530:Cyprinidae / Q000502:physiology*; D004192:Discrimination, Psychological; D007858:Learning
keywords: ANS; Approximate number system; Core number system; Numerical cognition