The Evolution of Collective Intelligence: A Comparative Approach

We repeatedly tested wild-caught individually marked guppies, Poecilia reticulata, in a y-maze and found that populations having evolved under different predation regimes displayed differences in their movement behaviour and degree of social information flow when making group decisions. In terms of decision-making performance, fish from low- predation environments decreased decision times at a greater rate over repeated trial rounds than fish from high-predation environments. This effect was only significant when fish were tested in groups of eight, not when tested individually. Low-predation groups increased social information transfer and made faster group decisions. High-predation groups also decreased decision time over trial rounds, despite not increasing social information transfer. We suggest that high- and low-predation populations decreased decision time via different mechanisms, one reliant on social information use (low-predation) and the other potentially through increased use of private information (high-predation). Predation pressure is a ubiquitous selective force and these findings may apply to a variety of natural social groups. Our results suggest decision-making performance can be increased via different mechanisms within the same species, depending on degree of selective pressure.