Ontogeny of numerical abilities in fish

Area of Science:

• Comparative psychology
• Animal behavior
• Neuroscience

Background:

• Human and primate numerical cognition involves separate systems for small (exact) and large (approximate) quantities.
• Fish exhibit numerical discrimination abilities comparable to primates, but whether these are innate or acquired remains unclear.

Purpose of the Study:

• To investigate the innate versus acquired nature of numerical discrimination in guppies.
• To determine the developmental trajectory of small and large quantity discrimination in fish.
• To explore the potential existence of separate numerical representation systems in fish.

Main Methods:

• Utilized guppies' natural tendency to join larger groups for quantity discrimination tasks.
• Tested newborn and juvenile guppies on discriminating small (2 vs. 3) and large (4 vs. 8, 4 vs. 12) quantities.
• Manipulated social experience by raising fish in pairs versus large groups to assess maturation and experience roles.
• Conducted control experiments to rule out non-numerical perceptual cues.

Main Results:

• Newborn guppies discriminated small quantities (2 vs. 3) but not large quantities (4 vs. 8, 4 vs. 12).
• Forty-day-old guppies discriminated large quantities (4 vs. 8) regardless of social experience.
• Twenty-day-old guppies discriminated large quantities only if raised in social groups, indicating a role for experience.
• Discrimination abilities persisted when non-numerical cues were controlled.

Conclusions:

• Small number discrimination in guppies appears innate, present from birth.
• Large number discrimination develops with age and is influenced by social experience, suggesting a maturational component.
• The developmental dissociation supports the hypothesis of distinct innate systems for small and large quantity representation in fish, paralleling primate systems.