“They’re also easier to use, I would argue, and easier to store. And it’s relatively cheaper to maintain and feed the fish.”
Another reason why zebrafish are ideal for his particular research, specifically behavioural research into mental disorders and addictions, is that they are very social, and in their natural settings are always found in shoals. “We use a variety of tests to measure basic movement, anxiety-like behaviour, boldness, and different types of memory, like episodic and object recognition memory,” Hamilton says.
An example is using a “novel object approach test” in which a Lego figurine is the novel object – never before seen by the fish.
Hamilton also dispels a myth. “Goldfish memory” is often used to describe a scatterbrained and forgetful individual based on the ( assumption that fish memory doesn’t extend beyond a few seconds. Research by Hamilton unequivocally proves that’s not the case.
“We have performed food-based reinforcement memory tests and shown that yellow cichlids can remember the cues associated with food reward for at least 12 days. We have also shown that zebrafish have a capable object recognition memory system that is enhanced by nicotine,” he says.
He also points to anecdotal evidence of sockeye salmon, who return from the oceans to the same freshwaters where they were spawned.
Unlike past researchers, Hamilton and his team have developed a method that allows them to administer fish with more precise doses of pharmacological substances, mimicking human consumption patterns. Some of the research, that tested the effects of substances such as nicotine and alcohol, brought results that are consistent with those found in humans.