The Hawthorne Effect: A Randomised, Controlled Trial

Department of Psychological Medicine, Imperial College London, UK. <>
BMC Medical Research Methodology (Impact Factor: 2.27). 02/2007; 7(1):30. DOI: 10.1186/1471-2288-7-30
Source: PubMed


The 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. Hawthorne Effects have been reported in previous clinical trials in dementia but to our knowledge, no attempt has been made to quantify them. Our aim was to compare minimal follow-up to intensive follow-up in participants in a placebo controlled trial of Ginkgo biloba for treating mild-moderate dementia.
Participants in a dementia trial were randomised to intensive follow-up (with comprehensive assessment visits at baseline and two, four and six months post randomisation) or minimal follow-up (with an abbreviated assessment at baseline and a full assessment at six months). Our primary outcomes were cognitive functioning (ADAS-Cog) and participant and carer-rated quality of life (QOL-AD).
We recruited 176 participants, mainly through general practices. The main analysis was based on Intention to treat (ITT), with available data. In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 140; mean difference = -2.018; 95%CI -3.914, -0.121; p = 0.037 favouring the intensive follow-up group), and on participant-rated quality of life score (n = 142; mean difference = -1.382; 95%CI -2.642, -0.122; p = 0.032 favouring minimal follow-up group). There was no significant difference on carer quality of life.
We found that more intensive follow-up of individuals in a placebo-controlled clinical trial of Ginkgo biloba for treating mild-moderate dementia resulted in a better outcome than minimal follow-up, as measured by their cognitive functioning.
Current controlled trials: ISRCTN45577048.

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    • "We believe therefore that the study reflects real-life EAEP in the ED. The predicted omission rate in the control group was much lower than anticipated by the local observational study pilot (80 % predicted vs 30 % observed).This may be explained by the Hawthorn Effect[28]and/or simulation artefact. Improved control group performance may have resulted in an underestimate of the effect size of the cognitive aids. "
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    ABSTRACT: Safety of emergency intubation may be improved by standardising equipment preparation; the efficacy of cognitive aids is unknown. This randomised controlled trial compared no cognitive aid (control) with the use of a checklist or picture template for emergency airway equipment preparation in the Emergency Department of The Royal Children’s Hospital, Melbourne. Sixty-three participants were recruited, 21 randomised to each group. Equal numbers of nursing, junior medical, and senior medical staff were included in each group. Compared to controls, the checklist or template group had significantly lower equipment omission rates (median 30 % IQR 20–40 % control, median 10 % IQR 5–10 % checklist, median 10 % IQR 5–20 % template; p < 0.05). The combined omission rate and sizing error rate was lower using a checklist or template (median 35 % IQR 30–45 % control, median 15 % IQR 10–20 % checklist, median 15 % IQR 10–30 % template; p < 0.05). The template group had less variation in equipment location compared to checklist or controls. There was no significant difference in preparation time in controls (mean 3 min 14 s sd 56 s) compared to checklist (mean 3 min 46 s sd 1 min 15 s) or template (mean 3 min 6 s sd 49 s; p = 0.06). Template use reduces variation in airway equipment location during preparation foremergency intubation, with an equivalent reduction in equipment omission rate to the use of a checklist. The use of a template for equipment preparation and a checklist for team, patient, and monitoring preparation may provide the best combination of both cognitive aids. The use of a cognitive aid for emergency airway equipment preparation reduces errors of omission. Template utilisation reduces variation in equipment location. Trial registration Australian and New Zealand Trials Registry (ACTRN12615000541505).
    Full-text · Article · Dec 2016 · Scandinavian Journal of Trauma Resuscitation and Emergency Medicine
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    • "Secondly, several studies reported that they failed to find any significant difference between manual and mechanical in their outcome of survival or survival to discharge. A possible explanation for these unexpected results advanced by the authors is a Hawthorne effect for manual CPR, which means a type of reactivity in medical rescuers modify or improve an aspect of their behavior in response to their awareness of being observed [42, 43]. Almost all of the included studies did not have the quality of CPR monitoring in place at the time, these data were not collected or reported specifics on how manual CPR was performed in the control group. "
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    Preview · Article · Dec 2016 · Scandinavian Journal of Trauma Resuscitation and Emergency Medicine
    • "For example, participants may have improved or modified an aspect of their behavior in response to the context in which they were acting rather than in response to the type of device used. This is known as the " Hawthorne effect "[37]. Fourth, the experimental setting cannot be considered as an ecologically valid one because the experiment took place in a controlled environment. "

    No preview · Article · Dec 2015
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