Pattern/Psychological Effect/No. 0458
Hawthorne Effect
The Hawthorne effect is a change in people’s behavior when they know they are being observed or taking part in a study. Named by Henry A. Landsberger in 1958 after Western Electric workplace research, it can affect study results; its size and direction vary.
- Evidence
- Mixed evidence
- Read
- 6 min
- Links
- 10 connections
01You've seen this when…
- in life
You send photos of your meals to a nutritionist for a week. Your lunches suddenly include more vegetables, even before you receive any advice.
- at work
A consultant shadows the warehouse team to measure packing errors. Everyone checks labels twice while she stands beside the conveyor.
- out in the world
Visitors sit at the back of a classroom to observe a lesson. Students who usually call out raise their hands; the room looks calmer than on an ordinary Tuesday.
02The idea
Warehouse staff may double-check labels. The classroom may be quieter. Neither necessarily shows what happens when the visitor leaves.
The Hawthorne effect is a broad label for behavior changes associated with knowing you’re being observed or taking part in research. Observation becomes part of the situation, not a neutral window onto it.
People often use the term to mean that attention makes people work harder. That’s too narrow. Being watched can make you more careful, more anxious, slower, more cooperative or more determined to resist. Different settings produce different responses.
The label covers several possible causes. One participant might notice a habit that usually runs automatically, while another might want to impress the observer or infer what the researcher expects. These explanations need to be tested individually.
This differs from the observer-expectancy effect: there, an observer’s expectations influence how a study is conducted or interpreted. Here, the person being observed changes behavior. Both can occur together.
03Why it happens
- Being watched makes judgment feel closer. A supervisor, researcher or clinician creates an audience. People may become more careful because their competence or reputation feels at stake. That’s evaluation apprehension.
- People try to present an acceptable version of themselves. Someone may actually drink less during a study, or merely report drinking less. The second is a reporting problem and leaves any change in behavior unproven. Social desirability bias can produce either misleading answers or pressure to change what others see.
- The study reveals what to pay attention to. A handwashing audit makes handwashing salient. A food diary makes snacks harder to overlook. Even without a visible observer, measurement can prompt reflection; the related question-behavior effect concerns changes associated with asking about behavior.
- Participation changes the surroundings. Extra visits, feedback, breaks or contact with staff may accompany observation. These can have effects of their own. When these changes arrive together, attributing an improvement to awareness of being watched requires evidence that separates their effects.
These are plausible routes, not ingredients of one universal effect.
04A worked example
In a study published in 2014, researchers at a Toronto hospital used an electronic monitoring system to record hand-hygiene dispenser use and the locations of human auditors. This let them examine what happened near visible auditors using a source of evidence separate from the auditors’ own counts.
What it looks like A human audit captures how reliably staff clean their hands during ordinary work. Observed performance can then stand in for performance throughout the ward.
What’s actually going on Dispenser-use rates were higher in hallways where auditors were visible than in comparison locations and periods. The pattern was consistent with staff changing behavior in the auditors’ presence. Dispenser use is an incomplete measure of correct hand hygiene: it leaves some occasions when cleaning was required uncounted. The study also left the exact reason for the behavior change unresolved.
What would have helped Interpreting visible audits together with measurements collected outside the auditors’ presence to check how well the audit represented ordinary practice. The electronic system helped reveal the discrepancy, while other measurement problems remained. Visible audits might still encourage safer behavior, but encouragement and measurement are different jobs.
05How to spot it
These clues call for investigation before drawing a conclusion. A temporary improvement can have several explanations.
06What to do about it
- Match attention across comparison groups. A control group should receive comparable observation and contact where practical. Otherwise you’re comparing the intervention plus extra attention against neither.
- Keep expectations from steering the test. Use blinding where feasible, and avoid announcing the desired result. Any withholding of study information must follow appropriate consent and ethical safeguards.
- Compare several kinds of evidence. Pair observation with routine records, outcomes and follow-up after the observer leaves. This triangulation helps reveal whether the apparent change survives a different way of measuring it.
- Give people time to settle into the setting. Repeated sessions may reduce novelty through habituation. Check whether behavior stabilizes; waiting alone leaves uncertain whether the effect has disappeared.
- Separate measuring from encouraging. If your goal is better hand hygiene, visible monitoring may help. If your goal is estimating ordinary practice, that same visibility can distort the estimate.
- Protect privacy while improving measurement. Less obtrusive methods remain subject to privacy protections against covert surveillance. Use justified, proportionate measures with appropriate consent, safeguards and oversight.
The practical question is whether your measurement changes the behavior you need to understand.
07Where it doesn’t invalidate the result
A study can yield valid results under observation. In a randomized experiment, the difference between groups can remain informative when both groups have similar participation effects. Problems remain if the intervention changes how strongly participants respond to observation.
A careful action under observation is still careful. The concern is whether it represents other settings, an issue of ecological validity, and whether the improvement lasts.
Finally, attributing an unexplained change to a Hawthorne effect requires evidence linking it to observation. Learning, fatigue, incentives, staffing and ordinary variation are competing explanations. Naming the pattern should open an investigation into what caused the change.
08Roots
At Western Electric’s Hawthorne Works in Cicero, Illinois, investigators began lighting experiments in 1924. The factory made telephone equipment, and the practical question was straightforward: could changing illumination improve workers’ output? Later studies examined other working conditions, including breaks and hours, with some workers assembling telephone relays in a separate test room.
The experiments became famous for a much tidier story: output supposedly improved whether the lights became brighter or dimmer, because workers knew they were being studied. The research involved changing conditions, incentives and relationships, leaving observation’s contribution mixed with other influences. Later reanalysis of the original lighting data challenged that familiar account.
In 1958, sociologist Henry Landsberger revisited the workplace studies and is generally credited with naming the Hawthorne effect. The phrase traveled from industrial research into medicine, education and product testing. Its usefulness outlasted the factory story: researchers still need to account for participation changing behavior. What hasn’t survived scrutiny is the claim that the original experiments proved a single, reliably positive effect of being watched.
09How solid is this?
Research supports behavior changes associated with observation or study participation in some settings, but their size, direction and mechanisms vary. Systematic review finds a heterogeneous evidence base, and reanalysis challenges the popular story about the original lighting experiments.
10Connections
- Often confused withObserver-Expectancy Effect, Mere Measurement Effect (Question-Behavior Effect)
- Countered byBlinding, Control Group, Triangulation, Randomized Experiment
- Part ofEcological Validity
- Includes Evaluation Apprehension
- See alsoSocial Desirability Bias, Habituation
11Origin and sources
Henry A. Landsberger is generally credited with naming the effect in Hawthorne Revisited (1958), interpreting Western Electric workplace studies conducted in the 1920s and 1930s.
- [1]Landsberger, H. A. (1958). Hawthorne Revisited: Management and the Worker, Its Critics, and Developments in Human Relations in Industry. Cornell University.
- [2]Levitt, S. D., & List, J. A. (2011). Was There Really a Hawthorne Effect at the Hawthorne Plant? An Analysis of the Original Illumination Experiments. American Economic Journal: Applied Economics, 3(1), 224–238.
- [3]McCambridge, J., Witton, J., & Elbourne, D. R. (2014). Systematic review of the Hawthorne effect: New concepts are needed to study research participation effects. Journal of Clinical Epidemiology, 67(3), 267–277.
- [4]Srigley, J. A., Furness, C. D., Baker, G. R., & Gardam, M. (2014). Quantification of the Hawthorne effect in hand hygiene compliance monitoring using an electronic monitoring system: a retrospective cohort study. BMJ Quality & Safety, 23(12), 986–993.
Suggest an edit· Updated 2026-10-02