Helmholtz (1821-1894) and Brunswik (1903-1955) are two scientists who were known for cue theories. Helmholtz held that the visual system constructs visual percepts through a process of unconscious inference, in which cues are used to make probabilistic best guesses about the state of the world. For Helmholtz (and most modern perceptual scientists), a visual percept is the manifestation of this process. Brunswik formalized Helmholtz's ideas with the lens model, which breaks the system's use of a cue into two parts: the ecological validity of the cue, which is its correlation with a property of the world, and the system's utilization of the cue. In these theories, accurate perception requires both the existence of cues with sufficiently high ecological validity to make inference possible, and that the system actually utilizes these cues in an appropriate fashion during the construction of percepts.
Some examples of visual cues include:
Some examples of auditory cues include:
Cue combination is an active area of research in perception, that seeks to understand how information from multiple sources is combined by the brain to create a single perceptual experience or response. Recent cue recruitment experiments have shown that the adult human visual system can learn to utilize new cues through classical (Pavlovian) conditioning.