There is a link between brain size and intelligence?
Quite possibly, but the findings are as yet ultimately inconclusive. You will find some scientists who swear that the bigger the brain, the more intelligent the person is. But such a thing is difficult to measure accurately. It's difficult to even agree what measure would matter the most.
Some studies suggest that the larger the frontal lobe in someone's brain, the more complex thought and reason they are capable of. Since that part of the brain is largely genetically and inherited trait, they scientists believed that they had found a connection between brain size and intelligence. Einstein's brain, it turns out was normal size, although the part that deals with mathematics was abnormally large.
Despite countless attempts to establish a link between brain volume of an animal with the degree of it's intelligence,it could not be reached a conclusion.
What has come out but was that the complexity of connections between neurons is what really matters. Researches on insects, living creatures with a so small and simply brain, have helped researchers to understand what happens in a much larger brain.Their opinion is, now, that "more does not mean necessarily better, in some cases can even be on the contrary".
Brain size seems to matter, in general,but not having any connection with intelligence. Even in terms of people, individuals with a common size brain, which have a high IQ, were compared with whales IQ, knowing that these have a brain that can reach up to 10 kilograms and a few billion neurons, but they are not at all more intelligent than people.
Intelligence is something which is not very clearly defined. Also there is no way to measure intelligence with precision. There are alternative ways of measuring intelligence and there may be considerable difference in measurement of intelligence of the same subject (a human being or an animal) by different methods. Also measurement of intelligence of the same subject using same method may result in significantly different measurements. Subject to these limitations of measuring intelligence, there is significantly high level of correlation between brain size of an animal in terms of brain volume or number of neurons and intelligence. As a matter of fact comparison of brain size is among many different methods used to compare intelligence of different animals.