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Individual differences, daily fluctuations, and developmental changes in amounts of infant waking, fussing, crying,
1London University Institute of Education.
Insights
Infant behavior, including sleeping, fussing, and crying, shows significant day-to-day instability. While development drives changes in waking and feeding, individual differences play a role in sleep and fussing patterns in infants.
Area of Science:
- Developmental Psychology
- Infant Behavior Studies
- Behavioral Pediatrics
Background:
- Infancy is characterized by rapid developmental changes and behavioral variability.
- Understanding the sources of variance in infant behaviors is crucial for developmental research and clinical practice.
- Previous studies have not fully disentangled developmental changes, individual differences, and day-to-day fluctuations in infant behaviors.
Purpose of the Study:
- To quantify the contributions of developmental changes, individual differences, and day-to-day fluctuations to infant sleeping, awake-content, feeding, fussing, and crying.
- To examine the stability of these behaviors across the first year of life.
- To compare the patterns of variance for different infant behaviors.
Main Methods:
- Multilevel analysis was used to examine infant behaviors at 2, 6, 12, and 40 weeks of age.
- The study analyzed the variance attributable to individual differences, age-related changes (development), and day-to-day fluctuations within infants.
- Key behaviors studied included sleeping, awake-content, feeding, fussing, and crying.
Main Results:
- Day-to-day fluctuations accounted for the largest proportion of variance in sleeping, fussing, and crying (44-53%).
- Developmental changes primarily explained waking and feeding, with no significant individual differences found.
- Individual differences and development each contributed about 25% to the variance in sleeping, showing moderate stability from 6 weeks to 9 months.
Conclusions:
- Infant behaviors exhibit significant instability, particularly in sleeping, fussing, and crying.
- Developmental trajectories are prominent in waking and feeding, while sleep and fussing show both developmental and individual difference components.
- Fussing demonstrates greater stability than crying, with early fussiness predicting later behavior, highlighting the importance of considering individual behavioral patterns.
Abstract:
Measures of the amounts of time infants spent asleep, awake-content, feeding, fussing, and crying at 2, 6, 12, and 40 weeks of age were examined using multilevel analysis. This method enables the proportion of the variance in each behavior due to individual differences to be compared to the proportion due to age changes (development) and to day-to-day fluctuations at each age in the same infants. Day-to-day fluctuations were found to account for the largest proportion of the variance in amounts of sleeping, fussing, and crying (between 44% and 53%), testifying to the importance of instability in these behaviors as a characteristic of infancy. Against this background, both development and individual differences explained substantial proportions of the variance, with a somewhat different picture in each area of behavior. Amounts of waking and feeding were mainly accounted for by development, and no evidence of enduring individual differences was found. For sleeping, development and individual difference each contributed approximately a quarter of the variance, and the amounts infants slept remained moderately stable from 6 weeks to 9 months of age. Crying decreased linearly with age, with development accounting for 38% and individual difference 15% of the variance. Fussing proved a more stable characteristic than crying, and "high fussers" at 6 weeks of age were particularly likely to retain this characteristic at 9 months, whereas amount of crying in the first 3 months did not predict 9-month behavior. The study's clinical, conceptual, and methodological implications are discussed.