Because intelligence has evolved independently in many different parts of the animal family tree, it’s likely to be something that is very useful for survival. Culum believes the factors that drive it are both environmental and social. “It’s fundamentally to do with your lifestyle, the problems you need to solve to get by and the environment you live in,” he says. For example, it could be influenced by having to find food in sophisticated environments. But it could also be helpful for processing social complexity. “You need a big brain to keep track of social relationships,” Culum adds.
An aspect of intelligence that has long interested Culum has been the way fish learn and remember. One experiment he did on rainbowfish, a popular aquarium species endemic to Australia and Papua New Guinea, involved a net that moved from one end of a fish tank to the other. The net had a single hole in it; to avoid getting trapped, the fish needed to find the hole quickly.
It took them only five goes to master the test. Furthermore, larger groups did better than smaller ones, suggesting they learn from each other via a process known as social learning. And, even though rainbowfish live for only two years, the test fish still remembered the skill 11 months later.
Social learning and memory are essential for any creature living in a large, complex-social group. Fish can spend most of their lives in shoals or schools. They must learn and memorise their shoal’s structure, remember their status within it and be able to recognise kin and familiars.
Having social learning allows the potential for transferring information between individuals and also between generations, leading to the development of ‘cultural traits’ or ‘traditions’ that can persist over time,