The most obvious difference between the brains of mammals and other vertebrates is in terms of size. On average, a mammal has a brain roughly twice as large as that of a bird of the same body size, and ten times as large as that of a reptile of the same body size.
Try to answer this question if possible (otherwise reply "unanswerable"): A mammal's brain is how many times larger than a birds relative to body size?
twice as large