Reproducing experiments on early verb understanding in infants

In this chapter, we describe an effort to reproduce the main result of the paper “Evidence for early comprehension of action verbs” by Nomikou et al. [1]. The study aimed at investigating the ability of 9-and-10-month old infants in under- standing verbs. The study in question followed a so called preferential looking paradigm consisting in investigating the ability to understand the meaning of words by testing whether infants look longer at a related stimulus compared to an unrelated stimulus. As a method to track looking time proportions to the target stimulus, an eye tracker was used. Data were collected from 9- to 10-month old infants who were presented with paired-picture trials while lis- tening to corresponding verbs. The infants saw two images on the screen side by side, each one from a different context category (CARE or PLAY). One of the pictures was related to the verb in question, while the other image was a confounder. The percentage of time that infants looked at the matching pic- ture, before and after having heard the verb, was recorded across participants, computing a difference score. In case the difference was positive, this was taken as evidence of understanding the meaning of the verbs. The study could only find a positive difference for 10-month olds but not for 9-month olds, showing that the ability to understand the verb in question emerges between 9 and 10 months. In close interaction with the authors of the original paper we rewrote the analysis scripts which were used by the authors to refine the results during a second iteration of reviewing in response to requests by reviewers. Overall, we could reproduce the central results of the study. This case represents a case of full analytical reproducibility.