A milkshake made dieters eat more ice cream, and what that says about one missed morning
The what-the-hell effect began with a 1975 milkshake study of dieters. What Herman and Mack measured, and what it does and does not say about never miss twice.
In this article7 sections
Picture the cover story. You are told you are rating ice cream flavors, and you are given ten minutes with three tubs. Before that, some of you were handed one milkshake, some two, some none. What the experimenters actually care about is how much you eat.
That was the setup in Herman and Mack’s 1975 paper “Restrained and unrestrained eating” (Journal of Personality, 43(4), 647-660). The result is the origin of what later became known as the what-the-hell effect: for people holding a strict rule about food, a breach of the rule can lead to eating more, not less. The finding was measured in ice cream. Whether it describes your alarm clock is a separate question, and this post tries to keep the two apart.
What Herman and Mack measured
The participants were sorted by an early version of the Restraint Scale, a questionnaire about dieting and concern over eating. In the abstract, the normal-weight participants are split into a “hypothetically deprived” high-restraint group and a “non-deprived” low-restraint group. Each person was then assigned to drink nothing, one milkshake, or two before the ice cream test.
The prediction was a crossover. Low-restraint eaters should behave as the old hunger-and-fullness model says: the bigger the milkshake, the less ice cream. High-restraint eaters, the dieters, should do the opposite, with intake rising as the preload grew. The abstract reports that this expectation was confirmed.
On size, I have only a secondary figure. A summary on the Society for the Study of Ingestive Behavior’s site reports that restrained eaters ate about 66% more ice cream after one or two milkshakes than after none, while unrestrained eaters ate about 47% less. I could not reach the paper’s tables, so I cannot give grams per condition or group sizes, and I am not going to guess at them.
The same summary says the results were adjusted for acute deprivation, meaning time since last eating and approximate calories. That matters, because the obvious objection is that dieters were simply hungrier.
A table of what has been read
| Source | What varied | What was measured | Read for this post |
|---|---|---|---|
| Herman & Mack, 1975, J Pers | Milkshakes: none, one, two | Ice cream eaten in a taste test | Abstract and secondary summary |
| Polivy, Herman & Deo, 2010, Appetite | Pizza slice that looked larger, smaller, or had no comparison | Cookies eaten afterward | Abstract |
| Polivy & Herman, 1985, Am Psychol | Review article | Argument that dieting precedes binge eating | Citation only |
| Cochran & Tesser, 1996, book chapter | Goal proximity and goal framing | Performance | Title only |
I could not get full text for any of the four. The table is a map of what stands behind the claims below.
The pizza slice that never changed size
The cleanest follow-up I could read is Polivy, Herman and Deo (2010, Appetite), “Getting a bigger slice of the pie.” Everyone was served the same slice of pizza. A third were led to think their slice was larger than another participant’s, a third that it was smaller, and a third saw no second slice. Then everyone “tasted and rated” cookies.
When the slice looked large, restrained eaters tended to eat more cookies and unrestrained eaters tended to eat fewer. Press coverage of the study reports 106 young women; the abstract I read does not give a sample size.
The pizza never changed. What changed was the belief about having overeaten, and the authors read their emotion data as pointing the same way. That is the mechanism worth keeping: the damage came through the story told about the slip, not the slip itself.
The 1985 American Psychologist paper “Dieting and binging: A causal analysis” extends this into an argument that dieting itself produces binge eating. I only know it from its citation and secondary descriptions. I know Cochran and Tesser (1996) only as a chapter in the book Striving and Feeling, on goal proximity and goal framing, and I could not read what they found. Those two stay out of the evidence here.
What never miss twice gets right
James Clear’s “never miss twice” rule in Atomic Habits (2018) says a single missed repetition is not the problem; a second one in a row starts a slide. I run the arithmetic on that in a two-log comparison. Read against the milkshake work, it is aimed at the right place. The ice cream data suggest the harm of a slip flows through what the slip is taken to mean, and the rule tells you in advance what it means: a single miss, not a verdict.
It also fits the habit side of the evidence. The Lally group at University College London, whose study I cover in the 66-day piece, reported that missing one opportunity did not materially affect habit formation. So one miss costs little in automaticity. The rule keeps the motivational cost from exceeding it.
Where the rule runs out
Two things the milkshake studies make awkward for the rule.
First, it asks you to apply a calm rule at the moment the what-the-hell reasoning is loudest. The participants in these experiments were not ignorant of their diets. They knew the rule and still ate more once it looked broken. A rule that depends on being in a reasonable mood after the miss is a rule that is weakest when needed.
Second, “twice” quietly licenses a first slip. For someone whose goal is rigid, that can turn the first miss into the very breach that starts the reasoning. Herman and Polivy’s boundary model, as I know it from secondary summaries, describes restrained eating as living inside a boundary, and the disinhibition shows up once the boundary is crossed. A streak counter that drops to zero is a boundary with a very visible edge. My reading, and it is an inference, is that goals counted in a single bright number invite this reasoning more than goals counted as a share of mornings. The pull of a finish line works similarly in the goal-gradient research: where the line sits changes behavior.
There is also the matter of scope. Everything above was measured in food, in laboratory taste tests, with people classified by a questionnaire. Unrestrained eaters showed the opposite pattern. Nobody here measured wake-up times.
The first missed morning
The point where the reasoning begins is easy to recognize. The alarm goes, you sleep through it or silence it, and by the time you are awake the thought is already assembled: the week is wrecked, the streak is gone, I will restart Monday. In ice cream terms, that is the second milkshake.
What the 2010 pizza result adds is that the belief matters more than the event. A consequence that has already fired changes what the belief can be. If a friend has seen the photo, the cost of the miss is paid, specific and finished, and the thought “nobody will know” no longer works. There is less left to hide, which leaves the next morning as a clean line item rather than the continuation of a failure.
DontSnooze is an alarm app that sends a random camera-roll photo to chosen friends when you do not record video proof after the alarm. It is built around that second case. No trial has tested whether it weakens the what-the-hell reasoning, and the argument cuts the other way too: a visible penalty could feed the sense of having failed, which the pizza study suggests is the active ingredient.
A practical version for a Tuesday
Nothing below is a tested protocol. It is what the evidence above supports.
- Write the response to a miss when you are calm, before any miss, in one sentence you can find on your phone.
- Name the size of the slip in numbers. “One missed morning of 21” is smaller than “I fell off.”
- Skip the make-up. No double workout, no extra early wake-up, since catch-up work rebuilds the feeling of being behind.
- Decide tonight’s alarm time before you put the phone down, and treat tomorrow as the next repetition.
- If you track a streak, also track a share, such as mornings up out of mornings tried, so that a zero is never the only number on screen.
The Lally finding says the single miss is cheap. The milkshake and pizza findings say the story told about it can cost more, and that story is the part you can prepare for ahead of time. The same logic of deciding before the loaded moment arrives is tested in the cake-or-fruit-salad experiment.