Hunter referred to such experiments as ones in which “you can only skin a fox once.” Whether the experimental problem does indeed have but one pelt must always be determined by experimentation. (See Hunter, W. S., & Bartlett, S. C. Double alternation in young children, /. exper. Psychol., 1948, 38, 558-567). Other examples of “one-shot” experiments can be found in the study if hidden figures in perceptual patterns. Still others are in several types of experiment on memory where the mere testing of retention may facilitate future performance on retention tests (for example, Brown, 1923)