Hello there @improv! Good points :)

All the 'good and bad' puppets played precisely the same short act for all the babies, and had no voice :) It is a silent puppet show. Further, one of the ways to control for preferences unrelated to behavior was counterbalancing the conditions :D (e.g placing the puppets in different order when present them for the babies to choose, using the same puppet to play the good and the bad guy and so forth). By all means have a look at the study to which link and full tittle I give in the in-text citation and the reference list. Personally, I think it is a wonderful study, which like every study has its strengths and limitations.

Excellent critical thinking though. Thank you for taking interest and the time to put forward insightful questions.

All the best to you.
Abigail.