Age of motor milestone onset was determined using parents’ checklist Roxadustat chemical structure diaries and corroborated via video coding. Mean age of the onset of pulling-to-stand was 8.68 months (range = 7.20–11.89 months; SD = 1.17). Mean age of cruising onset was 9.79 months (range = 8.05–12.59 months; SD = 1.07). Six infants began to walk before the conclusion of the study, with one beginning to walk during the second postcruising session (range = 10.91–12.95 months; SD = 0.88). The average time frame between the onset of cruising and the onset of walking was 77.33 days (range = 49–99 days;

SD = 16.49). Age ranges fell within the expected normal developmental range (Bayley, 1993; Piper & Darrah, 1994). To ensure that changes in infants’ reaching were associated with the onset of cruising and not another coincident upright motor milestone, all analyses were run twice, both including and excluding the infant whose walking onset coincided with the second postcruising session. There were no differences for any outcome measure whether data from this infant were included Hydroxychloroquine in vivo or excluded, so all reported analyses are inclusive. The mean number of reaching trials

per infant in each session was 18.50 (range = 15–20). Infants averaged 180 total reaching trials across all observation sessions (range = 108–188). Immune system Pooled data from all participants across all sessions yielded 3,969 total reaching episodes. The majority of infants’ reaches were unimanual; only 25% (n = 992) were bimanual reaches. On average, infants reached bimanually on 24% of trials (range = 0–65%; SD = 15.39). For each infant, reaching pattern preference

was calculated by averaging all reaching trials performed at each session, for a total of 7 pattern preference scores. A score close to (+1) indicates a very strong bimanual preference, while a score close to (−1) indicates a very strong unimanual preference. A score close to (0) represents no reaching preference. Index scores ranged from −1 (absolute unimanual) to 0.9 (strong bimanual). A 2 (gender) × 2 (trial type: midline vs. dual presentation) × 7 (session) repeated-measures ANOVA on reaching pattern preference revealed no main effects for trial type or gender. Therefore, trial type and gender will be collapsed across all subsequent analyses. Figure 2 illustrates a significant quadratic main effect for session, F(1, 24) = 12.26, p < .01, η = 0.34. The quadratic trend suggests, and a series of post hoc, least significant difference, pairwise comparisons confirms, a strengthening of unimanual reaching from sessions 2 to 3, a peak at session 3, followed by a weakening of unimanual reaching, especially in session 7.