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Collective learning in fish schools

With: Noam Miller and Iain Couzin

From fish schools to grade schools, most learning takes place within a social context. Group dynamics may influence what an individual learns about its environment. Conversely, individuals' learned knowledge may impact group dynamics, resulting in a complex interplay between the information held by individuals and the behavior of the group. We are using a combination of experiments and modeling to explore this collective learning process.

When learning occurs in a group context, do all individuals learn equally? For example, when fish within a school learn to associate a light with food, do all individuals learn to move to the light, or do some simply follow the others to the food? If learning is a costly process, it may be advantageous for an individual to copy the behavior of others rather than to learn itself, resulting in a dynamic analogous to the producer-scrounger model of social foraging theory. On the other hand, if resources are scarce, following others may not be a good strategy, since those who learn are likely to arrive at the resource first and dominate the food supply.

Through experiments and modeling, we are investigating the impact of varying resource levels on the dynamics of collective learning. In our experiments, schools of zebrafish decide which direction to go in a Y-maze, where one direction always leads to food. Fish are individually marked with colored implant elastomer tags so that we can differentiate them (see image above).

Below is a video from one trial. For this group, the green arm is "correct." 

And here is an underwater view, taken with a GoPro, just for fun. The camera is pointing down the green arm of the maze, which contains a feeding ring with food in it. The surface of the water behaves like a mirror due to total internal reflection!