Imagine that you’re taking an IQ test. You’re asked questions that assess a range of cognitive domains, such as verbal comprehension, perceptual organisation, working memory, processing speed… and the list goes on. If you reckon you did well in one cognitive domain of the imaginary IQ test you just took, chances are you did pretty well in the rest of them too.
A remarkable aspect of human psychometric test batteries is that scores between tests of different cognitive domains are positively correlated. In fact, human psychometric test battery performance is underpinned by a “general factor”, called g (for general intelligence), that typically accounts for 40-50% of the variance in task performance. Evidence for human g was first reported well over a hundred years ago.
By contrast, there has been little research into whether g exists in non-human animals. In particular, we know very little about the structure of intelligence in birds. Luckily, however, wild North Island robins are very willing psychometric test subjects.
Robins participated in a test battery that used six established measures of avian cognitive performance: a motor task, colour and shape discrimination, reversal learning, spatial memory and inhibitory control. Much like human test subjects, individual robins varied greatly in their ability to solve the tasks. Analysis of their performance in the test battery revealed that birds that did well in one task were likely to do well in the other tasks.
Strikingly, a general cognitive factor, analogous to human g, underpinned cognitive performance and explained over 34% of variance in the robin test battery. There is still a long way to go in terms of developing a truly comprehensive test battery for birds, but this result suggests that their cognitive performance may share a similar structure with humans. The next step will be adding tests that can tap into more cognitive domains, to get a fuller picture of how these little bird brains think about the world.