I believe that the interpretation of this experiment is a case of leaping to a foregone conclusion. I temper this however with the acknowledgment that social dominance is indeed possible between human beings because human beings are capable of comparing one moment or one point-of-view to another. Thus it takes a certain amount of mental development before an infant can be surprised by an interaction between two blocks wherein the bigger block “yields” to the smaller one.
In the meantime however there is a far more parsimonious explanation that should first be eliminated before we conclude that infants understand social dominance, especially since the researchers are also talking about the intuitive grasp of physics that babies are born with. Because the blocks have been “personified” with eyes and a face, it’s presumed that the infant is judging the interaction as if it is between two people. But before one can respond coherently and vicariously to what’s happening between two-dimensional images on a screen, is to first induce the phenomenon of emotional projection. The eyes of the block instinctively create a “being” as it accords a “negative” to the block’s “positive,” its bulky shape and motion, this allows the baby to project into the blocks and have a vicarious experience. In my model what makes human beings so incredibly social, and which dogs share to a degree, more so than any other animal, is the capacity to project their “self” (physical center-of-gravity as the seed of the emotional center-of-gravity) into inanimate objects. This requires the capacity to divine a negative or predatory aspect around which a coherent response can crystallize. For example, I don’t believe any other animal gazes at the moon and construes a species-specific face from its surface features. Therefore what’s distinctly human in this experiment isn’t necessarily the concept of social dominance, but rather the capacity of the baby to project her “self” into inanimate objects that have a form and a predatory aspect and I believe being able to do this in terms of a two-dimensional abstract image is what takes time to neurologically develop, well before any comprehension of social dominance could exist in a child's mind.
With this in mind the simplest interpretation of this experiment is that the infant girl projects her self into the two blocks and by way of intuitive physics, can feel the relative forces of mass, motion and resistance that are in play in this interaction. These same laws of motion, mass, resistance, will go on to frame her adult experiences when she projects into other people and which will then allow her to make emotional sense of inter-personal interactions and relationships. She will be able to feel how much energy someone is investing in what they’re saying, doing and feeling, and then whether or not she resonates with these forces will be the amount of motion she feels moved by what they do or say. For example, she may be in class one day being given some information that meets with objects of resistance (judgments) that she has acquired through her own experience. But if there's something about the teacher and the nature of the delivery that resonates within, as well as the logic stream of the information, then the resistance melts and she feels moved by this information. She relives the physical memory of pure flow and harmonic motion and now has a new perspective on the subject.
In my view, in this experiment the infant baby is feeling the relative forces of motion because she has been induced to project into the images by way of their personification and the result of the interaction feels incongruent because according to physics the larger block should have displaced the smaller one given that they were moving with the same momentum. In other words, she's feeling how an external system is working in terms of her own internal emotional process. Her "self" is both blocks, she's not judging one block relative to the other. Therefore the next experiment should be a small block moving very fast so that it’s momentum is enough to knock down the resistance of the large block as simple force mechanics would predict. As long as the shock effect of the collision can be factored out, we might see that a slow, large block being knocked out of the way by a very fast moving small block makes perfect sense to an infant by way of their intuitive grasp of physics and so there's no need to invoke a complex social psychology to account for the infant's prolonged gaze when an interaction doesn't proceed according to what "feels right" in her gut.