This study uses a within-participant experimental manipulation. All participants will be exposed to all utterances types (across trials).

Children will participate in screen-based language processing and word learning tasks in which they hear utterances with different types and amounts of linguistic simplification (i.e., a within-group manipulation).

LWL involves a child looking at a screen with two images, one on each side of the screen, while being provided an auditory cue that includes the name of the target image. The primary outcome is a dichotomous variable indicating whether the child is fixated on the target image or the distracter image; gaze directed at neither image will be considered missing. It will be determined whether gaze is to the left or right image, using trained coders who are blind to target side. Gaze location will be observed every 33 ms from 300 ms after onset to 2000 ms after target word onset, for a total of 51 observations per trial. Analyses will focus on differences across trial types and child characteristics in the trajectory of gaze location over the course of the trial.

A secondary outcome measure will be gaze location during the Teaching Phase of the Fast Mapping task (Study 2b). The variable is a dichotomous variable indicating whether the child is fixated on the novel image (only a single image is presented in each trial during the Teaching Phase) or not. It will be determined whether gaze is directed to the novel image, as our prior attempts to manually code single-object trials have not been successful. Only children who successfully calibrate and provide adequate automatic eye-tracking data in the Fast Mapping task will be included. Gaze location will be observed every 33 ms during the Teaching Trials. Analyses will focus on differences across trial types (single-word vs. full, grammatical teaching utterances).