Maximal response to a mechanical leader at critical group size in ant collectives

TL;DR

This study experimentally demonstrates that ant groups exhibit maximal collective response at a critical group size, supporting theories that biological collectives operate near criticality to optimize responsiveness.

Contribution

The paper provides the first direct experimental evidence that ant collectives respond most strongly at a critical group size, using a robotic system to mimic external stimuli.

Findings

Maximal response observed at critical group size

Experimental validation of criticality in collective response

Response amplification aligns with theoretical predictions

Abstract

It is widely recognized that biological collectives operate near criticality to amplify their capability of collective response. The peak in susceptibility near criticality renders these groups highly responsive to external stimuli. While this phenomenon has been recognized and supported by evidence from theory, a direct experimental demonstration has been elusive. To bridge this gap, here we record the response of a group of Paratrechina longicornis ants to external stimuli as they join efforts to carry food to their nest. Using a robotic system that mimics a transient leader, we apply tactile ant-scale forces and measure the group's response at sub, near, and supercritical regimes. Supported by theory and simulations, we provide direct experimental evidence to demonstrate that at critical group size, the collective response of the ants to an external force is maximally amplified.