In the first ManyBabies project, we replicated a robust finding from developmental literature: infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). IDS is characterized by a higher pitch, greater pitch excursions, and shorter utterances when compared to ADS. Exposure to IDS has been shown to improve word segmentation and word learning. We asked if infants have a preference for IDS, and how this preference varies across age, native language background, and method. Sixty-nine labs from 16 countries participated and collected data from 2,329 infants (range: 3-15 months old). We focused on three primary methods for assessing infants’ interest: single-screen central fixation, eye tracking, and the head-turn preference procedure (HPP).
Forest plot of the meta-analytic results for infant-directed-speech preference. The standardized effect size [x axis] is shown for each lab and age group [y axis]; error bars indicate 95% confidence intervals. Effects are grouped by method [colors]: central fixation, eye tracking, or head-turn preference procedure (HPP). Larger plotted points correspond to greater inverse variance. For each method, the diamond and associated error bars represent the meta-analytic estimate from the method-moderated model and the estimate’s 95% confidence interval. The top diamond shows the global meta-analytic estimate and 95% confidence interval from the unmoderated model.
The lines on this plot shows fitted values from a mixed effects model predicting looking time [y axis] from trial number [x axis], age [columns], method [rows], trial type [IDS red vs. ADS blue], and language group [NAE dark vs. non-NAE light].
lt =transpose(lt_fits)age_groups = ["3-6 mo","6-9 mo","9-12 mo","12-15 mo"]nae_vals =newMap([["North American English (NAE)","NAE"], ["Not North American English (non-NAE)","non-NAE"]])td =transpose(trial_data)
viewof points = Inputs.toggle({label:"Show data points"})viewof nae = Inputs.checkbox(nae_vals, {value:Array.from(nae_vals.values())})