The impact of errors in infant development: Falling like a baby

Abstract

What is the role of errors in infants' acquisition of basic skills such as walking, skills that require immense amounts of practice to become flexible and generative? Do infants change their behaviors based on negative feedback from errors, as suggested by "reinforcement learning" in artificial intelligence, or do errors go largely unmarked so that learning relies on positive feedback? We used falling as a model system to examine the impact of errors in infant development. We examined fall severity based on parent reports of prior falls and videos of 563 falls incurred by 138 13- to 19-month-old infants during free play in a laboratory playroom. Parent reports of notable falls were limited to 33% of infants and medical attention was limited to 2% of infants. Video-recorded falls were typically low-impact events. After falling during free play in the laboratory, infants rarely fussed (4% of falls), caregivers rarely showed concern (8% of falls), and infants were back at play within seconds. Impact forces were mitigated by infants' effective reactive behaviors, quick arrest of the fall before torso or head impact, and small body size. Moreover, falling did not alter infants' subsequent behavior. Infants were not deterred from locomotion or from interacting with the objects and elevations implicated in their falls. We propose that a system that discounts the impact of errors in early stages of development encourages infants to practice basic skills such as walking to the point of mastery.

Keywords: errors; falling; negative feedback; reinforcement learning; walking.

Figure 1.

Conceptualization of fall severity, method, and data coding. (A). Pyramid of fall severity. Tiers 1–2 represent epidemiological research based on medical reports of death, hospitalization, and out-patient medical care. Tier 3 represents our parent reports of minor injuries. Tiers 4–5 represent our coding of real-time infant and caregiver responses to infant falls. (B). Number of boys and girls who contributed at least one fall across age (total N = 138). (C). Number of falls contributed by each infant (M = 4.08) by walking experience. Symbols denote individual infants; colors represent age groups. (D). Fisheye views of laboratory playroom. Left panel shows the room set up with a couch and several elevations (colored in red) and several standard toys. Caregivers were instructed to play with infants as they normally would. Right panel shows the same room with a different set of standard toys but no furniture or elevations (only flat ground). Caregivers sat on the edge of the room and did not interact with infants. A third room set up was identical, but no toys were available. In all three room set ups, the experimenter (not shown) stood at the corner of the room and recorded infants’ movements with a hand-held camera. (E) Time course of an exemplar fall (top panel) and a deliberate transition to the floor (bottom panel) from one infant. Top panel: Numbers indicate elapsed time from loss of balance to first body impact, last body impact, recovery and return to play, and re-initiation of locomotion. Bottom panel: Numbers indicate elapsed time from start of transition to the floor, moment body was on the floor, and re-initiation of locomotion.

Figure 2.

Measures of fall severity. (A). Infant and caregiver reactions to falls. Top panel and inset: Percent of falls in which infants fussed (red bars), caregivers showed concern (blue bars), both occurred (purple bars), or neither occurred (green bar). (B). Infant recovery time (time for infant to return to normal play activity after a fall). (C). Recovery time when infants fussed, caregivers showed concern, both occurred, or neither occurred. Letters denote significant differences (ps < .05) among fall outcomes.

Figure 3.

Infants’ reactive behaviors after losing balance. (A) Time course of four types of reactive behaviors after losing balance in one exemplar fall (reactive steps, grabbed nearby supports, flexed knees in landing, and arrested the fall with outstretched hands). Colored numbers indicate the elapsed time from loss of balance to each reactive behavior. (B) Histogram of reactive duration (from losing balance to first body impact) categorized by number of different reactive behaviors (0–4) after infants lost balance. Colors represent the number of different types of reactive behaviors involved in the fall. (C) Histogram of reactive duration categorized by number of reactive steps infants took after losing balance. (D) Latency between losing balance and hand impact. Colors represent the order of hand impact in the entire body-impact sequence (1 denotes hand was the first body part to impact ground, 2 denotes hand was the second body part, etc.).

Figure 4.

Sequence of body impacts during (A) forward, (B) backward, and (C) sideways falls. Video frames show the most common body-impact sequences for forward and backward falls and a representative sideways fall. The bubble strings show every observed body impact sequence that occurred in more than 1% of falls and all sequences that involved head impacts. The relative frequency (out of all falls) of each body impact sequence is represented by the area of the bubbles. Each bubble denotes one body impact; bubbles are split in two or three sections to represent simultaneous impact of two or three body parts. Bubble color represents body part involved in the impact (“cool” colors denote less risky body parts, “warm” colors denote more risky body parts).

Figure 5.

Infant body factors that mitigate fall impact relative to an average U.S. adult. (A) Height and weight. Scatterplot shows that older infants and boys were generally taller and heavier than younger infants and girls. Inset shows that adults are 2 times taller and 8 times heavier than infants. (B) Potential energy of falls (Joules). Top panel: Average potential energy generated by infants’ falls while standing versus walking or running on the floor. Error bars denote standard errors. Bottom panel: Estimated energy generated by falls if infants had the body size and movement speed of an average U.S. adult. Note, adult data taken from the literature.

Figure 6.

Activity before and after falling. Data were normalized to each fall in 30-s time windows. All falls included the time from the moment infants lost balance until the time infants recovered balance and returned to play. Post-fall time windows began at the moment of recovery for (A), (C), and (D), and at the moment locomotion resumed for (B). Red lines denote mean activity in each time window. (A-B) Accumulated time in motion. (C) Percent of time interacting with the object implicated in the fall. (D) Percent of time visiting the elevation where the fall occurred. Error bars denote +/− one standard error. Gray areas represent range of activity.