Certainty and the cognitive ecology of generalization of predator recognition

Prey exposed to unknown species have the ability to label them as predatory if they are closely related to a predator already known to the prey. This phenomenon is coined generalization of predator recognition. While increasing the threat level of the known predator widens the generalization window (i.e. prey respond to species that are more distantly related), nothing is known about whether or not certainty associated with the identity of the known predator affects the generalization window. Here, we compared the generalization of tadpoles that were conditioned once (low certainty) or five times (high certainty) to recognize the odour of a rainbow trout, Oncorhynchus mykiss, and subsequently tested them for their response to rainbow trout, brown trout, Salmo trutta (closely related), brook trout, Salvelinus fontinalis (more distantly related) or goldfish, Carassius auratus. We found that the window shifted in two opposite ways, with high-certainty tadpoles responding more to brown trout but less to brook trout, when compared to their low-certainty counterparts. Our results highlight the nonlinear nature of stimuli generalization. We discuss potential mechanisms for our results and provide directions for future research aimed at understanding the role of uncertainty in antipredator decision making.