Relative versus absolute numerical representation in fish: Can guppies represent "fourness"?

Area of Science:

• Comparative Cognition
• Animal Behavior
• Numerical Cognition

Background:

• Operant conditioning allows diverse species to discriminate between different set sizes.
• Numerical discrimination tasks can be solved using either absolute or relative numerosity rules.
• Understanding numerical cognition in fish can provide insights into the evolution of number sense.

Purpose of the Study:

• To investigate whether fish can perform both absolute and relative numerosity judgments.
• To test fish's ability to generalize numerical discriminations to novel contrasts.
• To determine the flexibility of numerical decision-making strategies in guppies.

Main Methods:

• Experiment 1: Guppies trained on 6 vs. 12 shapes, tested with novel contrasts (6 vs. 3, 12 vs. 24).
• Experiment 2: Guppies trained to select 4 shapes against various alternatives (e.g., 4 vs. 1, 4 vs. 8).
• Generalization tests with novel, more difficult contrasts were conducted for both experiments.

Main Results:

• In Experiment 1, fish spontaneously used a relative numerosity rule, selecting novel quantities.
• In Experiment 2, fish successfully learned to identify a specific number (absolute rule) and generalized.
• Guppies demonstrated flexibility, adapting to either relative or absolute numerical criteria based on training.

Conclusions:

• Fish, specifically guppies, can learn and apply both relative and absolute numerosity rules.
• The choice of strategy (relative vs. absolute) depends on the experimental context and training.
• This study highlights the cognitive flexibility of numerical processing in fish.