A subtler hint, such as suggesting that the person examine the spaces between the trees, preserves more of the challenge. It changes the search strategy without directly revealing the answer. Once the appropriate region receives enough attention, recognition may occur naturally.
People should not interpret the speed of that recognition as a reliable measurement of intelligence. Hidden-image puzzles are recreational visual challenges, not standardized intelligence assessments. A person who discovers the face within seconds has not thereby demonstrated greater general intelligence than someone who needs several minutes. Performance can be
