Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations.

Which of the following two alternatives is more probable?

1. Linda is a bank teller.
2. Linda is a bank teller and active in the feminist movement.

Rationally, statement 2 cannot be more likely than statement 1, but in a 1983 study by Amos Tversky and Daniel Kahneman, fully 85 percent of respondents said that it was.

Why this happens is a matter of some debate. Tversky and Kahneman argued that in making this kind of judgment we seek the closest resemblance between causes and effects (here, between Linda’s personality and her behavior), rather than calculating probability, and that this makes statement 2 seem preferable.

Left: a basket of roses made of butter, by Frederick Nicholson, general manager of the Sussex Dairy Company, Brighton. “At one exhibition at which this basket was shown, several ladies and others stooped down to smell the flowers, quite thinking they were looking at a basket of real, yellow roses.”

Right: A dahlia and roses made of lard. “The dahlia … has sixty-two petals, each one of which has to be fashioned separately and then frozen, before the flower can be built up. It seems it is far more difficult to make flowers out of lard than out of butter, on account of the former substance being much softer and more oily. Mr. Nicholson says it takes him three minutes to make a rose-bud; four minutes to make a tuberose; five minutes to make an arum lily; six minutes to make a full-blown rose, and no less than three-quarters of an hour to make a dahlia.”

(From Strand, February 1898)

At Amsterdam, in a street called the Wood Market, recently lived a man who was curious in keeping fowls. One of his hens, though in the midst of summer, had several days stopped yielding her usual produce, and yet made her usual cackling; he searched the nest, but could not find even the shell of an egg, which made him resolve to watch her closely. He accordingly, the next day, placed himself in such a situation as to be able to observe her motions minutely; when, to his great surprise, he saw her discharge her egg; but no sooner was she off the nest, than three rats made their appearance. One of them immediately laid himself on his back, whilst the others rolled the egg upon his belly, which he clasped between his legs, and held it firm; the other two laid hold of his tail, and gently dragged him out of sight. This wonderful sagacity was exhibited for several days to some curious observers.

— London Globe, quoted in The Retrospective Review, 1826

Yesterday, at about five o’clock in the afternoon, when the daily labours in this mine were over, and all the workmen were together awaiting their supper, we saw coming through the air, from the side of the ternera, a gigantic bird, which at first sight we took for one of the clouds then partially darkening the atmosphere, supposing it to have been separated from the rest by the wind. Its course was from north-west to south-east; its flight rapid and in a straight line. As it was passing a short distance above our heads we could mark the strange formation of its body. Its immense wings were clothed with a grayish plumage, its monstrous head was like that of a locust, its eyes were wide open and shone like burning coals; it seemed to be covered with something resembling the thick and stout bristles of a boar, while on its body, elongated like that of a serpent, we could only see brilliant scales, which clashed together with a metallic sound as the strange animal turned its body in its flight.

— “Copiapo (Chili) paper,” quoted in The Zoologist, July 1868