Response threshold variance as a basis of collective rationality

Area of Science:

• Behavioral Ecology
• Neuroscience
• Social Systems

Background:

• Collective decision-making is crucial in various systems, from social insects to human societies.
• While social insects often use quality-graded responses for collective choice, brains rely on simple 'yes/no' neuronal responses.
• Existing models struggle to explain collective rationality in systems with binary (yes/no) decision units.

Purpose of the Study:

• To elucidate the fundamental mechanism enabling collective rationality in simple decision-making units.
• To demonstrate that this mechanism is employed by a specific ant species.
• To show how collective rationality can be achieved without quality-graded individual responses.

Main Methods:

• Theoretical modeling of collective decision-making with binary units and response thresholds.
• Experimental binary choice experiments with colonies of the ant *Myrmica kotokui*.
• Analysis of individual ant worker thresholds in relation to option quality.

Main Results:

• A larger number of binary units responding 'yes' to the best option leads to its selection by majority rule.
• *Myrmica kotokui* ant colonies demonstrated a preference for the better option in binary choice experiments.
• Individual ants exhibited variable response thresholds, contributing to the colony's collective choice.

Conclusions:

• Collective rationality can emerge from simple 'yes/no' decision units through a majority-based mechanism with variable thresholds.
• This mechanism explains how ants achieve optimal choices and has broad implications for understanding collective intelligence in brains, robotics, and human societies.