michael vassar: imagining a histogram of intelligence in multi-cell animalia by species (ignoring insects), there is a definite peak centered in the mouse-to-horse range, and the drop-off on the high intelligence side is steep and down-curving to vertical. Many top or middle predators are dog-smart. Beyond that, parrots, crows, monkeys, dolphins, octopi... widely scattered in taxa, but rare enough to name. A gap. Higher apes. A gap. Chimps. A big gap. Humans. And nothing.

This may be no more than my bias speaking, because it's not real data. Still, it looks pretty obvious to me that there's some serious difficulty crossing the dog-to-hominid gap. Otherwise, intelligence would be more smoothly spread out.