Poster #155 - Crawl, cruise, stand, then walk? Individual differences in motor skill acquisition

• In Event: 3-159 - Poster Session 12
  In Poster Session: PS 12 Section - Perceptual, Sensory, Motor

Integrative Statement

Research on infant motor development often relies on onsets—ages when infants first demonstrate new skills. Most studies that collect onset data tend to focus on particular motor skills (e.g., just crawling and walking) rather than charting their developmental progression. Studies about individual skills result in averages for specific behaviors but often sacrifice information about individual differences in the timing of successive motor skills.

Current methods used to pinpoint when infants acquire new skills are not standardized. Individual labs define onset criteria for purposes of particular studies and typically use one of several different approaches for data collection. Most commonly, researchers identify onsets with retrospective parent report. Some labs use structured interviews, asking caregivers to recall the first time their infant performed selected motor skills (e.g., Adolph, 1995). Others provide questionnaires that caregivers complete on their own. Onsets are also tracked prospectively (e.g., Adolph et al., 2003; Atun-Einy et al., 2011). Infants are enrolled before the expected skills and caregivers are provided calendars and checklists to track developmental change. Given known issues with accuracy of recall and potential problems of construct validity with prospective parent report, either approach on its own is not sufficient.

We addressed these methodological considerations in two ways. First, to increase rigor in data accuracy, we derived a corpus of motor skill onsets by leveraging (1) prospective parent report, (2) experimenter confirmation, and (3) video from a cohort of 30 infants visited in the home every two weeks from 2 to 19 months of age. Second, to uncover individual differences in patterns of motor skill acquisition, we determined the onsets of four skills: crawling, cruising, standing, and walking. Crawl onset was operationalized as continuous motion on hands and knees (or feet) for 3 cycles; cruise onset was defined as 5 continuous upright steps with hands supported by furniture; stand onset was credited when infants remained upright for a minimum of 10 s without support; and walk onset required 5 continuous independent steps without stopping or falling.

Replicating existing findings, crawling occurred at 8.62 months (range = 6.31-12.33, SD = 1.42), cruising at 9.69 months (range = 6.77-12.66, SD = 1.27), standing at 10.93 months (range = 8.28-14.17, SD = 1.31), and walking at 11.98 months (range = 8.74-14.86, SD = 1.31). However, as shown in Figure 1, our approach revealed immense individual differences. Though a predominant trajectory—crawl, cruise, stand, then walk—was demonstrated by 21 infants, the acquisition and timing of each motor skill was not obligatory. One infant crawled after she walked, 3 infants stood before they cruised, 2 infants stood and cruised at the same time, 2 infants cruised before they crawled, and 1 infant never crawled. Precocious crawlers cruised earlier (r = .653, p < .01), stood earlier (r = .637, p < .01), and also walked earlier (r = .404, p < .05).

Overall, we propose that a more rigorous approach, utilizing converging evidence from multiple sources, is necessary when identifying onsets in motor development.

Authors

• Joshua L. Schneider, University of Pittsburgh
  Presenting Author

• Jana M Iverson, University of Pittsburgh
  Non-Presenting Author