''Animal intelligence correlates with X"
But since what we care about is suffering and not intelligence, we're implying that more intelligence = more suffering, which if true would mean that hurting a children or a baby causes less suffering than hurting an adult.
Yet I would argue that the opposite seems to be true given that intelligence allows us to cope and contextualize and understand our suffering better than a child.

At best, there is no correlation between intelligence and suffering.
At worse, the opposite is true.