We chose those particular time points based on standard practices in the literature for taking assessments of an outcome measure immediately prior to a target event, followed by subsequent repeated assessments post-target event (Metcalfe et al., 2004; Pemberton MK-8669 order Roben et al., 2012). We did not have data for one infant’s second session postcruising. Repeated-measures ANOVAs comparing infants’ Pattern Preference Index scores at the four sessions revealed no main effect for session for pulling-to-stand, F(3, 72) = 1.00, NS, but did reveal a significant main effect for session for cruising, F(3, 69) = 10.09,
p = .01, η = .20 (see Figure 3). Pairwise comparisons showed a significant difference between the session at cruising onset and both postcruising onset sessions, where infants showed a significant increase in bimanual reaching patterns after cruising onset, p = .02 and p < .01, respectively. There was also a significant
difference between the session prior to cruising SB203580 datasheet onset and the second postcruise onset session, p = .01. A cluster analysis classified participants into groups based on reaching pattern preference strength based on the z-scores of: The frequency of using two hands on total reaching trials per infant; Individual standard deviation of the Pattern Preference Index over time. Within-subject variance averaged 0.35 (range = 0.00–0.61; SD = 0.13); and The percentage of the seven observations for each infant in which a bimanual and unimanual preference
was documented (Index score > 0.5). The analysis revealed three groups: Strong unimanual (n = 6); Fluctuations in preference (n = 14); No preference (n = 5; see Table 2 and Figure 4). Kruskal–Wallis tests comparing the three groups found no differences between the groups in age of pulling-to-stand onset, cruising onset, gender, or hand preference. Infants with a Strong profile reached almost exclusively unimanually over the course of the study, as defined by over 90% of their sessions with a Pattern Preference score greater Clomifene than −.50; infants with a Fluctuations profile were unstable in their preference for unimanual or bimanual reaching from session to session, averaging four fluctuations over the course of the study; and infants with No preference primarily hovered between −.5 and .5 on the Pattern Preference Index at each session, with at least three sessions with a Pattern Preference Index of 0 (equal number of reaches with one and both hands in the same session). Two infants reflected the extremes of these profiles, with one showing an exclusive unimanual preference over the entire study and another showing a consistent weak preference for bimanual reaching over the course of the study.