A doctor was lecturing a group
of medical students and informed them that the presence of too much sugar in
urine can be detected by tasting the urine. He demonstrated by sticking his
finger into a urine sample, and then putting his finger in his mouth, after
which he stated that the sample was too sweet. He then asked each student to
try.
The students went up, one-by-one, and tested for themselves, and while some
agreed with the doctor, others weren’t sure. What no one noticed, however, was
that while the doctor had put his middle finger into the sample, he had put his
forefinger into his mouth. The test wasn’t a test for the sample, but was a
test of perception.
