Flückiger, Christoph; Del Re, A. C.; Wampold, Bruce E. (2015). The sleeper effect: Artifact or phenomenon—A brief comment on Bell et al. (2013). Journal of consulting and clinical psychology, 83(2), pp. 438-442. American Psychological Association 10.1037/a0037220
Full text not available from this repository. (Request a copy)OBJECTIVE:
Bell, Marcus, and Goodlad (2013) recently conducted a meta-analysis of randomized controlled additive trials and found that adding an additional component to an existing treatment vis-à-vis the existing treatment produced larger effect sizes on targeted outcomes at 6-months follow-up than at termination, an effect they labeled as a sleeper effect. One of the limitations with Bell et al.'s detection of the sleeper effect was that they did not conduct a statistical test of the size of the effect at follow-up versus termination.
METHOD:
To statistically test if the differences of effect sizes between the additive conditions and the control conditions at follow-up differed from those at termination, we used a restricted maximum-likelihood random-effect model with known variances to conduct a multilevel longitudinal meta-analysis (k = 30).
RESULTS:
Although the small effects at termination detected by Bell et al. were replicated (ds = 0.17-0.23), none of the analyses of growth from termination to follow-up produced statistically significant effects (ds < 0.08; p > .20), and when asymmetry was considered using trim-and-fill procedure or the studies after 2000 were analyzed, magnitude of the sleeper effect was negligible (d = 0.00).
CONCLUSION:
There is no empirical evidence to support the sleeper effect.
Item Type: |
Journal Article (Review Article) |
|---|---|
Division/Institute: |
07 Faculty of Human Sciences > Institute of Psychology > Clinical Psychology and Psychotherapy 07 Faculty of Human Sciences > Institute of Psychology |
UniBE Contributor: |
Flückiger, Christoph |
Subjects: |
100 Philosophy > 150 Psychology 600 Technology > 610 Medicine & health |
ISSN: |
0022-006X |
Publisher: |
American Psychological Association |
Language: |
English |
Submitter: |
Adriana Biaggi |
Date Deposited: |
14 Apr 2015 16:29 |
Last Modified: |
05 Dec 2022 14:45 |
Publisher DOI: |
10.1037/a0037220 |
URI: |
https://boris.unibe.ch/id/eprint/67360 |
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