I didn’t realize that was scientific consensus. So that would imply that brains under a certain size are incapable of higher levels of intelligence? I don’t think that’s right... I thought the consensus was that brain size has no strong correlation with intelligence at all. That makes sense considering how neurons work, the connections they form seem like they would be more causal.
The scientific consensus is that from the evolutionary perspective, brain/body size is absolutely correlated with performance. This doesn't have to be general intelligence, but can be sensory processing ect.
That is not to say that structure isn't important too. This is especially relevant because the study observed some of the structural changes through to be associated with increased intelligence as well.
Its a complicated question. Within the human species, the correlation is not that strong at all. In cross-species comparisons it tends to be quite strong, especially when considering brain to body weight ratios. Bird brains may be an interesting exception however, which I suspect can be quite intelligent, depending on how intelligence is measured.
Part of what makes that interesting is we are very good at some tasks that might be quite expensive, and really bad at some tasks that could be simple. In other words, our personal views on difficulty could be wildly off. For example assuming computer vision should be easy and chess hard.
Information processing is limited to the capacity of the network. So it is easy to see that very small brains cannot be very smart (there is no set of connections that can make fruit fly human-intelligent). However, having a large capacity network doesn’t mean it will result in high intelligence. So it’s necessary but not sufficient.
