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The stability of individual differences in infant attachment: comments on the Thompson, Lamb, and Estes contribution
Insights
Infant attachment security shows surprising instability, with only 53% of infants maintaining classifications across two key developmental periods. This challenges previous findings on attachment stability in middle-class infants.
Area of Science:
- Developmental Psychology
- Attachment Theory
Background:
- Attachment security is typically considered stable in infant development.
- Previous studies reported high stability in infant attachment classifications.
Purpose of the Study:
- To evaluate the stability of infant attachment classifications.
- To investigate discrepancies in attachment stability findings between studies.
Main Methods:
- Analysis of infant attachment classifications using the Ainsworth Strange Situation at 12.5 and 19.5 months.
- Comparison of results with previous research on attachment stability.
Main Results:
- Only 53% of middle-class infants maintained the same attachment classification (avoidant, secure, or resistant) between 12.5 and 19.5 months.
- Low stability contrasts with previous findings, with sample differences suggested as a potential factor.
Conclusions:
- The stability of infant attachment may be lower than previously reported, particularly in diverse samples.
- Methodological differences and sample characteristics can influence observed attachment stability.
- Further research using quasi-experimental designs with heterogeneous populations is recommended to inform developmental theory.
Abstract:
In a recent article, Thompson, Lamb, and Estes reported that only 53% of middle-class infants seen in the Ainsworth Strange Situation at 12.5 and 19.5 months received the same attachment classification (avoidant, secure, or resistant) at both ages. Thompson et al. suggest that differences between their results and very high levels of stability reported by Waters can be attributed to subject selection that minimized the incidence of family stress and maximized the possibility of finding stability in the earlier study. In fact, Waters did not employ any procedure for maximizing stability beyond the use of a middle-class sample. Stability of individual differences in infant attachment is a well-replicated finding. Nonreplication in a single small sample is difficult to evaluate. Among the possible explanations, sample differences are weak and necessarily post hoc as explanations for the low stability reported by Thompson et al. It is suggested that when populations are heterogeneous with respect to significant influences on development, quasi-experimental comparisons among well-defined elements of the population and relevant control groups can inform developmental theory; correlational data from small unselected samples cannot.