I'm an ECE who's worked with toddlers for quite a while, and I have to question the methodology here.
Adults interpretations of the motivations of toddlers and babies aren't reliable enough to form the basis of such a conclusion - they are always colored by those adult's basic view of children in general, and of that specific child. E.g. I've often seen adults who've assumed that a child is feigning deafness, while the child might as well just have been very concentrated on something else.
The conclusion might be right, but they need to find a better way of studying it. I actually clicked this because I was curious about the methodology.