Tracking changing environments: innovators are fast, but not flexible learners

Abstract

Behavioural innovations are increasingly thought to provide a rich source of phenotypic plasticity and evolutionary change. Innovation propensity shows substantial variation across avian taxa and provides an adaptive mechanism by which behaviour is flexibly adjusted to changing environmental conditions. Here, we tested for the first time the prediction that inter-individual variation in innovation propensity is equally a measure of behavioural flexibility. We used Indian mynas, Sturnus tristis, a highly successful worldwide invader. Results revealed that mynas that solved an extractive foraging task more quickly learnt to discriminate between a cue that predicted food, and one that did not more quickly. However, fast innovators were slower to change their behaviour when the significance of the food cues changed. This unexpected finding appears at odds with the well-established view that avian taxa with larger brains relative to their body size, and therefore greater neural processing power, are both faster, and more flexible learners. We speculate that the existence of this relationship across taxa can be reconciled with its absence within species by assuming that fast, innovative learners and non innovative, slow, flexible learners constitute two separate individual strategies, which are both underpinned by enhanced neural processing power. This idea is consistent with the recent proposal that individuals may differ consistently in 'cognitive style', differentially trading off speed against accuracy in cognitive tasks.

Figure 1. Schematic of innovation tasks.

Each bird was tested on a pseudorandom selection of two tasks amongst those depicted in a–d. All birds were also tested on the task depicted in e. See text for more details.

Figure 2. Relationship between innovation performance and discrimination learning.

Innovation performance was calculated as the mean latency to solve three different extractive foraging tasks (see Figure 1). Learning performance was measured using the total number of 20-trial blocks to reach a learning criterion (see text for more details). Open circles indicate female mynas, filled circles indicate male mynas.

Figure 3. Relationship between innovation performance and reversal performance.

Each panel depicts this relationship for one of four successive reversals. Innovation performance was calculated as in Figure 2. Reversal performance was measured using a reversal score, expressed as the total number of 20-trial blocks to reach criterion on a given reversal relative to the total number of 20-trial blocks to reach criterion on the initial discrimination (see text for more details). Open circles indicate female mynas, filled circles indicate male mynas.