Seeing what you expect

Introduction: Researchers tested whether information on a label changes how good a drink tastes.

Participants: Ninety adults aged 21 to 70 (51 women and 39 men) shopping at a large supermarket in Chicago, Illinois, who agreed to take part in a tasting. Race/ethnicity was not reported.

Method: Each participant tasted two cups of orange juice. Both cups held the same juice, but one was labeled "Fresh-squeezed premium juice, $6.99" and the other "Store-brand juice from concentrate, $1.99". Which cup was tasted first was randomly decided. Participants rated how good each juice tasted (1 = very bad, 10 = excellent). Finally, participants tasted two unlabeled cups, one of real fresh-squeezed juice and one of store-brand juice, and tried to pick out the fresh-squeezed one.

Results and Discussion: Participants rated the juice labeled premium higher (mean of 7.4) than the identical juice labeled store brand (5.9), a statistically significant difference. In the unlabeled test, 52% picked the fresh-squeezed juice correctly, close to the 50% expected by guessing. When told the first two cups held the same juice, 38% of participants said they didn't believe it.

Introduction: Researchers tested whether looking at one kind of picture changes how people see a drawing that can be seen in two ways.

Participants: 120 students (68 women and 52 men) aged 18 to 24 at a university in Singapore. Race/ethnicity was not reported.

Method: Participants were randomly assigned to look through a series of 12 photographs of either birds or small furry animals such as rabbits and squirrels, for 5 seconds each. They then saw, for 2 seconds, a simple line drawing that can be seen either as a bird's head facing left or as a rabbit's head facing right. Participants wrote down the first thing they saw.

Results and Discussion: After looking at birds, 81% of participants reported seeing a bird. After looking at small furry animals, only 23% reported seeing a bird; the rest reported a rabbit. The difference was statistically significant. When later shown a clear photograph of a bird, every participant in both groups identified it correctly.

Introduction: Researchers tested whether being told what to look for changes how experts and beginners read medical X-ray images.

Participants: Twenty-four experienced radiologists (doctors who specialize in reading medical images; 10 to 30 years of experience) and 24 third-year medical students at a hospital in London, England. Race/ethnicity was not reported.

Method: Each participant examined 40 chest X-rays. Twenty showed a real small lung growth and 20 did not, as confirmed by later tests. For a randomly chosen half of the X-rays, a note said, "Patient referred for possible lung growth." For the other half, the note said only, "Routine check." Participants reported whether they saw a growth in each X-ray.

Results and Discussion: When the note mentioned a possible growth, the medical students reported a growth in 31% of the X-rays that had none, compared with 12% with the routine note. For radiologists, these rates were 8% and 7%, which did not differ significantly. Both groups found slightly more of the real growths when the note mentioned one, and radiologists found more real growths overall (88%) than students (61%).