Chimpanzees (Pan troglodytes) accurately compare poured liquid quantities.

Area of Science:

• Cognitive Science
• Animal Behavior
• Comparative Psychology

Background:

• Previous research indicates nonhuman animals can discriminate discrete quantities.
• Limited research exists on nonhuman animals' ability to discriminate continuous quantities.

Purpose of the Study:

• To investigate chimpanzees' ability to discriminate continuous quantities (liquids).
• To compare discrimination performance for continuous versus discrete quantities.
• To assess the impact of presentation methods and visual illusions on quantity discrimination.

Main Methods:

• Chimpanzees performed quantity judgments on liquid amounts in three experiments.
• Tasks involved visible and non-visible liquid quantities.
• Presentation methods included pouring and dispensing liquids, with varying heights to create potential visual illusions.

Main Results:

• Chimpanzees succeeded in all continuous quantity discrimination tasks.
• Performance showed similarities to discrete quantity tasks, notably ratio-dependent accuracy.
• Chimpanzees accurately judged quantities regardless of visibility or presentation-induced visual illusions.

Conclusions:

• Chimpanzees possess robust quantitative discrimination skills for continuous quantities.
• These skills are comparable to their abilities with discrete quantities.
• Chimpanzees are not easily misled by perceptual manipulations when judging quantities.