Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Psychology

Program Name/Specialization

Behavioural Neuroscience

Faculty/School

Faculty of Science

First Advisor

Dr. Noam Miller

Advisor Role

Supervisor

Abstract

This thesis addresses how animals cope with unpredictability by testing how environmental stability changes the behaviour of zebrafish (Danio rerio) in two complementary experiments. In Experiment 1, fish lived for three months in either a Dynamic environment (water temperature, feeding times, habitat complexity, group size, and membership fluctuated) or a Stable environment (all factors constant). Across seven behavioural assays, measuring individual behavioural differences, collective movement, social memory, and information use, Dynamic condition fish were found to be more sensitive to social cues and more likely to conform to recent social information, independent of the quality of the information itself. They also maintained social motivation and swam closer together, but were less coordinated in shoals. These results suggest that when conditions change frequently, older information degrades quickly, while recent information becomes more valuable. Social stimuli may also become more salient because social information allows for faster updating in changing conditions.

In Experiment 2, to test whether social stability drove these effects, I isolated group membership and manipulated group phenotypic composition. Fish were housed in either a stable homogeneous group (similar personalities), a stable heterogeneous group (mixed personalities), or in groups with membership that changed every other day. Extending three assays from Experiment 1, I examined consistent individual behavioural differences (personality) and collective movement while controlling for familiarity. Fish from dynamic social environments increased the most in boldness and decreased the most in sociability (contrary to Experiment 1), and were the most repeatable in both traits, becoming the most extreme and rigid in personality, likely because continuous role-shifting is costly. Fish from the Dynamic condition were again closer together and less coordinated in shoals than those from one of the Stable conditions (similar to Experiment 1), independent of familiarity, showing that social instability alone can disrupt schooling in fish. Shoals composed of bolder fish were also more coordinated. Lastly, living in heterogeneous groups pushed for conformity, while homogeneous groups did not change meaningfully in either trait.

In rapidly changing environments, information quickly becomes outdated, and conspecifics provide the most recent information. This thesis shows that zebrafish adjust their decision-making strategies and both individual and collective behaviour to adapt to unpredictable conditions, offering insight into the mechanisms and possibly implications of behavioural plasticity in an increasingly unpredictable world.

Convocation Year

2026

Convocation Season

Spring

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Available for download on Wednesday, March 25, 2026

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