“babies too young to speak or understand intentions root for justice.”

The study design appears to have attempted to account for potential procedural bias (but I'm not a psychologist / psychology researcher).

That being said, does this not imply that a sense of justice is independent of, and perhaps one of the foundations for society, rather than society being the source of justice..Sort of the difference between natural law and common law at some level(??) :D

From the research article, the experimental procedure:

"Stimuli: Two familiarization animation scenarios were created using Poser 6.0 (e-frontier Inc.). In the familiarization scenario, each geometric cube agent (green or orange) with eyes, which was within a white bounded enclosure, watched an aggressor–victim interaction outside this enclosure in which one geometric spherical figure with eyes (aqua coloured) hit and crashed into another similar-looking (but yellow) figure. After this aggressive interaction, the cube agents (green and orange) either interfered in the interaction at the top of the display (interfering event) or did not interfere at the bottom of the display (non-interfering event) (Fig. 1a, Supplementary Videos 1 and 2). The two types of familiarization events (41 seconds in duration) were presented four times in alternate order (that is, the roles of the different coloured cubes and the presentation orders of the two familiarization animations were counterbalanced between participants). Following the familiarization phase was a forced-choice task in which infants were presented with two real cube objects corresponding to the colours and features seen in the animation (each cube was 6.5 × 6.5 × 6.5 cm). The presentation position of these two objects (left or right) was counterbalanced between participants."