Effects of stimulus size and spatial organization on pigeons' conditional same-different discrimination

Area of Science:

• Animal cognition
• Behavioral neuroscience
• Visual perception

Background:

• Pigeons previously learned same-different visual discrimination based on item identity, cued by background color.
• This study investigates how variations in stimulus size and spatial arrangement affect this discrimination behavior.

Purpose of the Study:

• To examine the impact of stimulus size variation on pigeons' same-different discrimination.
• To assess the effect of spatial organization (vertical vs. horizontal alignment) on discrimination performance.
• To determine if physical and spatial changes affect accuracy and reaction time in multi-item array discrimination.

Main Methods:

• Two experiments were conducted using pigeons trained on a same-different visual discrimination task.
• Experiment 1 tested generalization across various item sizes within 7-item arrays.
• Experiment 2 tested discrimination with items grouped in different spatial locations (top, bottom, left, right).

Main Results:

• Pigeons demonstrated near-perfect accuracy (stimulus generalization) across all tested item sizes and spatial arrangements.
• Reaction times showed pigeons perceived different sizes of a single icon as the same stimulus.
• Vertical arrangements were processed faster than horizontal arrangements.

Conclusions:

• Pigeons' same-different discrimination accuracy remained high despite changes in item size and spatial organization.
• While pigeons detected physical and spatial stimulus variations (indicated by reaction times), these changes did not impair their ability to discriminate array sameness or difference.
• These findings highlight the robustness of pigeons' abstract same-different concept in visual multi-item arrays.