In 1939, a psychology experiment proved that words from someone in a position of authority could permanently change a person's behaviour. It's not a historical curiosity. The same basic mechanism has since been measured, directly and repeatedly, inside modern healthcare.
The Monster Study
The experiment was run by Wendell Johnson, a University of Iowa researcher testing a theory of his own: that stuttering wasn't something a child was born with, but something that could be created by how the adults around them talked about their speech. His graduate student, Mary Tudor, tested it on 22 orphan children at the Iowa Soldiers' Orphans' Home. Some of the children were completely normal, fluent speakers. They were told for months that their speech was starting to show the beginnings of stuttering, and that they needed to fix it immediately, with orphanage staff instructed to reinforce the criticism between Tudor's own visits.
Several of them developed real, lasting stutters. It didn't wear off, either. At least one of the children developed a stutter that stayed with her for the rest of her life. Not because anything changed in their mouths or their brains. Because of what they were told. Johnson's own colleagues at the university were the ones who named it. They found what he'd done to healthy children so disturbing that some compared it to Nazi human experimentation, and warned him it would end his career if he ever published it. He never did.1
Now, no clinician today is running anything close to what Johnson did. But the underlying mechanism, a label from someone in authority changing how a person's body actually behaves, isn't unique to 1939. It comes across daily in the language we use with our clients: during an assessment, in giving someone a clear understanding of their pain without invoking fear or fragility, in how we prescribe exercise, and in whether someone avoids the gym entirely because they believe they can't meet some "perfect" exercise standard.
The same mechanism in modern healthcare
A well-known qualitative study interviewed 23 people with acute and chronic low back pain about where their beliefs about their own spine actually came from. Healthcare professionals had a stronger influence on those beliefs than the internet, family, or friends, and the effects lasted for years.
When clinician language got interpreted as "your back is vulnerable and needs protecting," people didn't just feel informed. They became hypervigilant, guilty when they couldn't stick to the protecting, frustrated when the protecting didn't work anyway. But the same influence ran the other way too. Genuine reassurance built real confidence, and clear encouragement to keep moving positively shaped how people approached activity for years afterward. The mechanism itself wasn't the problem. What clinicians actually said with it was.2
What's written on a scan can do the same thing
Phrases like "bone on bone," "your spine is degenerating," or "you've got the back of an 80-year-old" aren't lies. Plenty of that imaging language is technically accurate. It's also often just normal age-related change, with no relationship to someone's actual pain, present in a large share of people who have never had a symptom in their life.3 Said to a person mid-flare, it doesn't land as anatomy. It lands as a verdict.
One large, real-world trial tested this directly. Radiologists added a short, standardised note to spine imaging reports for older adults: a line stating what percentage of pain-free people the same age typically show the very same findings on a scan. Nothing about the scan itself changed, and nothing about how it was read changed either. Only that one added line of context did, and it meaningfully altered what happened next in someone's care: less follow-up imaging, fewer opioid prescriptions, fewer procedures.4 Nobody's anatomy changed. Only the words describing it did.
It's also a key reason we don't recommend a scan unless the result will genuinely change what we do next. Imaging ordered without a clear clinical indication is linked to worse outcomes, not better ones. In a randomised trial, patients who received routine spine X-rays for low back pain were more likely to still be in pain months later than those who weren't scanned, despite feeling equally satisfied with their care in the meantime.5 In workers' compensation data, early MRI without a clear indication has been linked to dramatically longer time off work, and to far more injections and surgery down the line, even after accounting for how severe the initial pain was.6
A core part of physiotherapy is being able to build a working diagnosis without a scan at all, using a thorough movement and symptom assessment as the primary evidence. When we do request imaging, it's to rule a specific diagnosis in or out, not because a scan feels like the only way to explain pain we can't otherwise account for. That distinction matters, because pathology shows up on almost every scan, even in people who are completely asymptomatic.3 A scan confirms or challenges what the movement assessment already points to. It isn't a substitute for one.
Perfect technique carries the same risk
The same pattern shows up in the gym. Many people are taught that their exercise technique needs to be close to perfect before it counts, and for some, that standard becomes a reason to avoid training altogether rather than risk getting it wrong.
There's a real, narrow window where that emphasis is genuinely appropriate. During an injury or a structured rehabilitation plan, biasing a specific technique, one that loads the muscles that need strengthening and protects a structure that's actually sensitised right now, is exactly the right approach. We'll push you toward that more precise version of the movement on purpose, for as long as it's actually needed. On what counts as a reasonable reference point outside of that context, see our piece on whether perfect movement actually exists.
For someone healthy and pain-free, chasing that same standard indefinitely tends to do the opposite of what it's meant to. People become so focused on doing it "right" that they simply do less: less loading, less variety, less exercise overall. The technique gets protected. The person underloads. And general underloading, over the long term, is worse for someone's health than an imperfect rep ever was.
The throughline
A 1939 psychology experiment, a modern radiology report, and a comment about your squat look like they belong in different conversations. They're not. Each one demonstrates the same basic mechanism, at wildly different scales of harm: a label from someone in a position of authority doesn't just describe a person's condition, it can change it.
In practice, that shapes a few concrete things about how we work. We explain a scan finding alongside how common, and how unrelated to pain, it usually is in people who feel fine. We order imaging only when the result will genuinely change what happens next, not because having one feels reassuring in the moment. And we describe a movement pattern as a reference point to build on, not a standard someone has failed to meet.
None of that means softening the actual clinical picture. It means being as deliberate with the words as we are with the treatment itself, because for the person on the other end of them, the words are very often what actually lands.
Masters of Physiotherapy, University of South Australia. Founded Move Physiotherapy in 2018. Provides match day services to sporting clubs across Perth, with a focus on evidence-based rehabilitation and objective return-to-sport testing.
References
- Silverman FH. The "monster" study. J Fluency Disord. 1988;13(3):225–231.
- Darlow B, Dowell A, Baxter GD, Mathieson F, Perry M, Dean S. The enduring impact of what clinicians say to people with low back pain. Ann Fam Med. 2013;11(6):527–534.
- Brinjikji W, Luetmer PH, Comstock B, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR Am J Neuroradiol. 2015;36(4):811–816.
- Jarvik JG, Comstock BA, James KT, et al. The effect of including benchmark prevalence data of common imaging findings in spine image reports on health care utilization among adults undergoing spine imaging: a stepped-wedge randomized clinical trial. JAMA Netw Open. 2020;3(9):e2015713.
- Kendrick D, Fielding K, Bentley E, Kerslake R, Miller P, Pringle M. Radiography of the lumbar spine in primary care patients with low back pain: randomised controlled trial. BMJ. 2001;322(7283):400–405.
- Webster BS, Bauer AZ, Choi Y, Cifuentes M, Pransky GS. Iatrogenic consequences of early magnetic resonance imaging in acute, work-related, disabling low back pain. Spine (Phila Pa 1976). 2013;38(22):1939–1946.