Ask somebody to name a fruit, quickly, and one answer arrives far more often than the hundreds available.
Name a fruit.
The first one that comes to mind. Type it.
Apple. Performers expect it, and this is one of the forces with real evidence underneath rather than tradition alone.
Fruit was one of the ten categories in Eleanor Rosch's typicality work, where 209 English speakers rated how good an example each item was. Apple sits at the center of the category and pomegranate at the edge, and people confirm apple as a fruit measurably faster than they confirm pomegranate.
Out of 0 answers so far. Free to quote, with the sample size beside it so a reader can judge the weight.
Once this passes 1000 answers, the measurement replaces the claim above as the headline of this page, and the claim becomes the thing being checked rather than the thing being reported. Saying that in advance is the point: a threshold decided afterwards is not a threshold.
The mechanism has a name and a literature. Eleanor Rosch showed in the 1970s that categories are not lists we search through — they have a center. Some members are better examples than others, people agree closely about which, and they answer measurably faster when the item is a good example. Her study collected 565 typicality ratings from 209 English speakers.
That is the whole of a psychological force. Ask somebody to answer quickly and you are not sampling the category at random — you are asking for whatever sits closest to its center. Speed is the instruction that does the forcing.
Not popularity exactly, and not familiarity alone. A prototype is the member that shares the most features with the rest of the category and the fewest with anything outside it. An apple is medium-sized, roughly round, sweet, grown on a tree, eaten raw, with skin you can bite through and seeds you do not eat.
A tomato fails on sweetness and on how it is used. A coconut fails on nearly everything except growing on a tree. Both are fruit; neither is a good example of one, and the difference shows up in how long people take to say so.
Write the prediction, ask the question, and show the card only when it is right. The value of the effect is the true rate, and the true rate is a measurement.
The fruit question has a particular quirk worth knowing: because the category has a clear center, the second and third answers tend to be much rarer than the first. A force with one strong answer and a long thin tail is a better bet than one with three contenders.
Apple is the expected answer, and unusually for a magician's force it has academic support. Fruit was one of the categories in Rosch's typicality work, and apple sits at the center of it.
The running count above tests whether that holds when people are asked quickly rather than asked to rate.
Because it is the best example of the category. A prototype shares the most features with the rest of the category and the fewest with anything outside it, and an apple is round, sweet, tree-grown, and eaten raw.
People confirm an apple as fruit faster than they confirm a pomegranate, which is the same effect a force exploits.
Botanically yes, and it rarely comes up when people are asked to name one, because it fails the everyday test: it is not sweet and it is not eaten as fruit.
It is a good illustration that categories in the head are organized around typical examples rather than definitions.
This is one of eleven questions in the full study, which asks for a card, a number, a vegetable, a fruit, an animal and more, and shows the running counts for all of them. The rest of the site is self-working card tricks you can play in the browser.