How do pigeons represent numbers? Studies of number scale bisection

Area of Science:

• Comparative Cognition
• Animal Behavior
• Numerical Cognition

Background:

• Understanding how non-human animals perceive and process numerical information is crucial for evolutionary psychology.
• Pigeons (Columba livia) have demonstrated sophisticated cognitive abilities, including numerical discrimination.

Purpose of the Study:

• To investigate pigeons' ability to bisect numerical ranges on two different scales (1-16 and 2-32).
• To determine whether pigeons represent numbers on a linear or logarithmic scale.
• To test the predictive power of an associative model with varying generalization assumptions.

Main Methods:

• Two experiments involving pigeons choosing between keys based on the number of preceding key pecks.
• Pigeons were trained to bisect scales at geometric means (Experiment 1) and arithmetic means (Experiment 2).
• Psychophysical functions and discrimination accuracy were analyzed using an associative model.

Main Results:

• Pigeons superimposed the two number scales and showed indifference at the geometric means in Experiment 1.
• Asymmetries in discrimination accuracy were observed in Experiment 2, varying with number magnitude.
• An associative model best predicted the data when assuming a logarithmic representation of number and constant generalization.

Conclusions:

• Pigeons represent numerical values on a logarithmic scale, consistent with Weber's law.
• The findings support an associative learning model with constant stimulus generalization for number representation.
• This study provides insights into the fundamental mechanisms of numerical cognition in a non-human species.