The authors present their results of a series of laboratory experiments on perceptual phenomena from which they derive the proposition that three basic adaptive processes operate in perception: selection, accentuation (emphasizing certain features), and fixation (persistence and preferential retention of certain selected percepts). Three selective mechanisms are proposed: selective sensitization (lower thresholds for acceptable stimulus objects), perceptual defense (higher thresholds for unacceptable stimulus objects, or defense against anxiety-laden stimuli), and value resonance (guesses about doubtful percepts will reflect