Stability of deferred imitation in 12- to 18-month-old infants: A closer look into developmental dynamics

Abstract

Deferred imitation is used to assess declarative memory in infants. Although a lot of studies show that infants from 6 months onwards are able to re-enact actions following a delay, only a few studies describe early declarative memory longitudinally. From a variable-centred approach, these studies found a modest relationship between measurement occasions that increases with age. However, no studies have analysed the differential aspect of memory development from a person-centred perspective. The present study analyses memory stabilities both from a variable-centred and person-centred approach within a sample of N = 87 infants of a 2-wave longitudinal design (12- and 18-month-olds). From a variable-centred perspective, the results indicate that, first, there was a significant increase in infants' memory performance and, second, that although reliable, the stability of infants' memory performance was relatively low. From a person-centred perspective two vs. three groups of infants were differentiated showing different developmental growth trajectories and stability correlations but no differences in language, cognitive and motor development. The implications of those results in terms of further test development are discussed. Furthermore, important methodological expansions for the analysis of infants' memory data are presented and discussed.

Keywords:

• Deferred imitation
• Infant memory
• Person-centred approach
• Stability of early declarative memory
• Variable-centred approach

Acknowledgments

This study was supported by a grant from the German Research Foundation (Deutsche Forschungsgemeinschaft) to MK (KN 275/3 – 1).

We would like to thank Regina Kressley-Mba for her help during the preparation of the study and we gratefully acknowledge the assistance of Christina Mack, Veit Kubik, Micha Best, Ali Koc, Margit Feyler and Eva Riedmueller for scoring the video tapes and helping with data collection. Special thanks are due to all the babies and their families who participated in the study.

Notes

¹The target action tin can had a baseline performance rate of 20.8% the target action toy pig with hat of 8.3%, the target action cup and knife of 29.2%, and the target action drum of 20.8% and the target action mouse of 4.2%.

²The target actions car, goose, frog, octopus had a baseline performance rate of 0%. The target action mouse had a baseline performance rate of 19.2% and the target action drum of 7.7%.

³Four raters rated the video tapes. Rater 1 and Rater 2 reached an interrater reliability of r = 96.1% (Cohen's kappa κ = .92), Rater 2 and Rater 3 an interrater reliability of r = 96.1% (Cohen's kappa κ = .92) and Rater 3 and Rater 4 an interrater reliability of r = 95.8% (Cohen's kappa κ = .91).