La cognizione numerica degli animali: il Teleosteo Gambusia Holbrooki come modello sperimentale

It has long been recognized that the ability to make numerical judgments predates the evolution of human language. In the last few decades, a large body of evidence has accumulated on numerical competence in mammal and birds, but little is known about the numerical abilities in lower vertebrates. The present research investigated numerical competence in fish, using both spontaneous choice test and training procedure. Results of free-choice test show that female mosquitofish seem to use two distinct systems for quantity discrimination; at the same time this study provides persuasive evidence that, when choosing between two shoals differing in numerosity, fish do not use numerical representation but rather base their choice on non-numerical variables that are correlated with group size. Training procedure demostrated, however, that fish can learn how to distinguish among 2 e 3 elements without attending the visual cues spontaneously considered in free-choice tests. To date, this research represents the first evidence in literature of numerical competence in fish.