Interconnected

It's not just primates that react to babylike features: some songbirds can be duped by fish who rise up above the water's edge and gape like baby birds. A gaping mouth is the feature that elicits parental behavior in birds, the avian equivalent of big heads and large eyes, and so the poor birds dip down and stuff food into the mouths of the fish instead of their own young. -- The Other End of the Leash by Patricia McConnell, page 123.