UNIVERSITÀ DEGLI STUDI DI PADOVA Sede Amministrativa: Università degli Studi di Padova Dipartimento di Psicologia Generale SCUOLA DI DOTTORATO DI RICERCA IN :Scienze Psicologiche CICLO: XXVI At the root of numerical cognition: fish as a model species to study pre - verbal numerical abilities. Direttore della Scuola : Ch.ma Prof. Francesca Peressotti Supervisore :Ch.mo Prof. Angelo Bisazza Dottorando : Maria Elena Miletto Petrazzini TABLE OF CONTENTS 1. INTRODUCTION ............................................................................................ 1 1.1. Numerical abilities in animals ...................................................................... 4 1.1.1. Field studies ........................................................................................... 4 1.1.2. Laboratory studies ................................................................................. 6 1.2. The role of continuous variables in quantity discrimination judgments ..... 10 1.3. One or multiple numerical systems of numerical representation ? ............. 17 1.4. Development of pre-verbal numerical abilities .......................................... 29 1.4.1. Developmental studies in humans ....................................................... 30 1.4.2. Developmental studies in animals ....................................................... 34 1.5. Numerical abilities in fish ........................................................................... 38 2. AIM OF THE RESEARCH ............................................................................ 45 3. THE SPECIES ................................................................................................ 49 Gambusia holbrooki ................................................................................... 49 Poecilia reticulata ...................................................................................... 50 Xenotoca eiseni ........................................................................................... 51 Betta splendens ........................................................................................... 52 Pterophyllum scalare .................................................................................. 53 Danio rerio ................................................................................................. 54 4. NUMERICAL ABILITIES IN ADULT FISH USING A TRAINING PROCEDURE ................................................................................................. 55 4.1. A new training procedure for studying discrimination learning in fish. ..... 55 4.1.1. Experiment 1: Influence of numerical ratio in large number discrimination .................................................................................................. 57 Subjects ....................................................................................................... 57 Apparatus .................................................................................................... 57 Stimuli ........................................................................................................ 58 Procedure .................................................................................................... 61 Results ........................................................................................................ 63 4.1.2. Experiment 2: Influence of total set size in large number discrimination .................................................................................................. 64 Subjects and procedure ............................................................................... 64 Results ........................................................................................................ 64 4.1.3. Experiment 3: Limit of small number discrimination ......................... 66 Subjects ....................................................................................................... 66 Stimuli and procedure ................................................................................. 66 Results ........................................................................................................ 66 4.1.4. Experiment 4: Influence of extended training on numerical discrimination .................................................................................................. 68 Subjects and procedure ............................................................................... 68 Results ........................................................................................................ 68 4.1.5. Discussion ............................................................................................ 70 4.2. Inter-specific differences in numerical abilities among teleost fish ........... 75 4.2.1. Experiment 1: Influence of numerical ratio and total set size in different fish species ........................................................................................ 78 Subjects ....................................................................................................... 78 Apparatus and stimuli ................................................................................. 78 Procedure ................................................................................................... 79 Results ........................................................................................................ 81 4.2.2. Experiment 2: Control test: shape discrimination test ........................ 85 Subjects, apparatus, stimuli and procedure ................................................ 85 Results ........................................................................................................ 85 4.2.3. Discussion ........................................................................................... 86 5. FACTORS AFFECTING NUMERICAL ABILITIES IN FISH ................... 91 5.1. Collective enhancement of numerical acuity by meritocratic leadership in fish .................................................................................................................. 91 5.1.1. Experiment 1: Spontaneous discrimination of shoals differing in numerosity ...................................................................................................... 93 Subjects ...................................................................................................... 93 Apparatus ................................................................................................... 94 Procedure ................................................................................................... 95 Results ........................................................................................................ 95 5.1.2. Experiment 2: Trained abilities to discriminate between sets of stimuli differing in numerosities ................................................................................. 98 Subjects ...................................................................................................... 98 Apparatus and stimuli ................................................................................ 98 Procedure ................................................................................................... 99 Results ...................................................................................................... 100 5.1.3. Discussion ......................................................................................... 102 5.2. Numerical acuity of fish is improved in the presence of moving targets, but only in the subitizing range ........................................................................ 104 Subjects .................................................................................................... 106 Apparatus and stimuli .............................................................................. 106 Procedure ................................................................................................. 108 Results ...................................................................................................... 110 5.2.1. Discussion ......................................................................................... 114 6. ONTOGENY OF NUMERICAL ABILITIES ............................................ 119 6.1. Development and application of a new method to investigate cognition in newborn guppies .......................................................................................... 119 6.1.1. Experiment 1: Ontogeny of gregarious behavior .............................. 122 Subjects .................................................................................................... 122 Apparatus ................................................................................................. 123 Procedure ................................................................................................. 124 Results ...................................................................................................... 124 6.1.2. Experiment 2: Preference between mirror image and real conspecifics ................................................................................................... 127 Subjects and apparatus ............................................................................. 127 Procedure ................................................................................................. 128 Results ...................................................................................................... 129 6.1.3. Experiment