A wide range of animal species, including humans, live and travel in cohesive groups. Group membership improves foraging success and reduces the risk of predation. When making a decision, members of groups have to balance their personal information and preferences with sometimes conflicting social information (derived from the behaviors of others) and their need to remain close to the rest of the group. As a result, individuals in groups may sometimes make behavioral choices they would have preferred not to, simply in order to remain with their group (for example, how many bad movies have you seen simply because all your friends wanted to?)

Our research considers both the mechanisms of collective behavior and how being in a group shapes individual cognition. Individuals that live in close proximity to others must perform all their cognitive functions within a group context. Social considerations can therefore have a decisive influence on individual cognition and behavior. We try to identify and measure these collective influences on cognition. Below are brief descriptions of some recent and ongoing research projects.

Mechanisms of collective movement

image: Noam Miller
Animals that move around in groups have to avoid crashing into each other, while also staying quite close together and synchronizing their motions. We found that zebrafish in groups will increase the distances between themselves and their neighbors when there is food in their tank and decrease the distance when a (simulated) predator has just been by [PDF] . We also found that zebrafish groups have regular oscillations in their distances from each other, possibly another way to avoid getting too close or too far from the group [PDF]. To begin to explore how the fish do all this, we exposed groups of zebrafish to varying concentrations of either alcohol or nicotine and measured how their collective movement changed. The different drugs, even at very low concentrations, affected the group in measurably different ways. [PDF] [Video]
Collective decision-making

image: Sean Fogarty
Animals have to make decisions (such as where to look for food) and animals in groups, in addition to moving together, have to make collective decisions, to ensure that the group stays (mostly) together. We trained two groups of Golden Shiners (pictured at left) to find food based on different types of cues. We then mixed the fish from both groups. By following the lead of the front few fish, such mixed groups were able to reach a consensus and search mostly in locations that contained both types of trained cues. [PDF] [Videos]

Collective learning

image: Noam Miller
When making decisions, either alone or in a group, animals rely on information that they have learned based on their past experiences with the environment. Animals in groups, making collective decisions, have to also take into account the preferences and learning of other individuals, which may conflict with their own information. This can alter the decisions they make, which affects the learning opportunities they have, and thus their future decisions. We modified a simple model of individual associative learning to show how collective behavior alters the contents of learning. [PDF]

Individual differences

image: Ariana Strandburg-Peshkin
In many animal species, including ourselves and fish, different individuals behave differently. This has been called a 'behavioral syndrome' or 'animal personality'. We are studying how these individual differences determine the behaviors of groups of zebrafish and how the composition of the group affects its cohesiveness and decisiveness. Colored fluorescent tags (as in the image to the left) allow us to identify and follow each individual fish. [PDF]

Mate choice copying

image: Noam Miller
One of the main challenges animals (including humans) face is choosing a mate. In some species (including humans), individuals avoid the costs of identifying a good mate by simply copying the mate choice of another individual - choosing the same or a similar mate. In collaboration with Dr. David White's lab, we examined how personality interacts with mate choice copying. We found that more social female guppies copy mate choices more than less social females. [PDF]