How do you measure the intelligence of an extinct animal? What we can say is that the intelligence of dinosaurs must have been sufficient for their way of life — otherwise they would not have survived for millions of years. Some plant-eating dinosaurs certainly had very small brains in proportion to their size. However, a large brain is not important in an animal which is too enormous to be attacked and has little to think about apart from grazing. On the other hand, some of the predatory dinosaurs had quite large brains, presumably because they needed to think quickly as they pursued their prey.
In comparison with their size, the brains of the smallest dinosaur predators were the biggest, because they needed to be agile and fast moving.
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