Developmental continuity? Crawling, cruising, and walking

Abstract

This research examined developmental continuity between "cruising" (moving sideways holding onto furniture for support) and walking. Because cruising and walking involve locomotion in an upright posture, researchers have assumed that cruising is functionally related to walking. Study 1 showed that most infants crawl and cruise concurrently prior to walking, amassing several weeks of experience with both skills. Study 2 showed that cruising infants perceive affordances for locomotion over an adjustable gap in a handrail used for manual support, but despite weeks of cruising experience, cruisers are largely oblivious to the dangers of gaps in the floor beneath their feet. Study 3 replicated the floor-gap findings for infants taking their first independent walking steps, and showed that new walkers also misperceive affordances for locomoting between gaps in a handrail. The findings suggest that weeks of cruising do not teach infants a basic fact about walking: the necessity of a floor to support their body. Moreover, this research demonstrated that developmental milestones that are temporally contiguous and structurally similar might have important functional discontinuities.

Keywords: crawling; cruising; developmental continuity; locomotion; walking.

Figure 1

Gaps apparatus used to test infants' use of upper and lower limb information. (A) Handrail-gap condition with adjustable gap in the handrail (0 cm – 90 cm) and a continuous floor. (B) Floor-gap condition with adjustable gap in the floor (0 cm – 90 cm) and a continuous handrail.

Figure 2

Cruising thresholds in the (A) handrail (N = 21) and (B) floor condition (N = 19).

Figure 3

Cruisers' attempts and exploration on safe and risky gaps. (A) Cruise ratio: (successful + failed attempts to cruise)/(successes + failures + refusals to cruise). (B) Exploratory limb extensions into gaps. (C) Latency to embark over gaps. Data are plotted according to relative amount of risk. The 0 point on the x-axis represents each infant's gap threshold in each condition. Baseline gap size was 2 cm in the floor-gap condition and 16 cm in the handrail-gap condition. Error bars represent standard errors.

Figure 4

Near-walkers' attempts and exploration on safe and risky gaps. (A) Walk/cruise ratio: (successful + failed attempts)/(successes + failures + refusals). (B) Exploratory limb extensions into gaps. (C) Latency to embark over gaps. Data are plotted according to relative amount of risk. The 0 point on the x-axis represents each infant's gap threshold in each condition. Baseline gap size was 2 cm in the floor-gap condition and 16 cm in the handrail-gap condition. Error bars represent standard errors.