Unconscious Perception

Different Types of Unconsciousness

Although Sigmund Freud is generally given credit for raising consciousness about unconsciousness, his brand—the psychoanalytic unconscious—is only one aspect. While Freud's conception of the unconscious deals primarily with appetitive urges and motivations, more recent work by researchers including John Bargh, Ap Dijksterhuis, and John Kihlstrom has focused on—and found empirical evidence for—cognitive and social processes that operate at an unconscious level. Many of the cognitive and social processes involved in unconscious perception have been revealed to be surprisingly sophisticated and complex and are discussed below.

Terminology

A variety of terms have been used to describe perception without awareness: unconscious perception, nonconscious perception, subception, implicit perception, and subliminal perception. The term limen (a root of subliminal) implies a threshold for consciousness. Philip Merikle and Jim Cheesman (1986) have most effectively defined this boundary as a subjective threshold, or “the level of discriminative responding at which observers claim not to be able to detect perceptual information at better than a chance level of performance” (p. 42). However, since the subjective threshold is based entirely on a perceiver's self-report, it should be combined with an additional criterion—performance that is qualitatively different during aware versus unaware episodes—which in turn permits distinguishing conscious from unconscious processes. Thus, the term implicit perception has recently gained popularity among cognitive neuroscientists, both because it avoids the logical problem created by the term subliminal (i.e., evidence suggests the existence of a continuum along the conscious-subconscious spectrum, not simply a threshold) and, according to John Kihlstrom and others, because subliminal perception is just one subcategory of unconscious perception. In particular, we shall see that unconscious perception covers a much wider range of phenomena than the narrower term subliminal. A PsycINFO search (June 2010) revealed 1,932 citations concerned with unconscious perception, in contrast to only 636 involving subliminal perception.

Unconscious Processes versus Unconscious Stimuli

Information can be unavailable to consciousness for many reasons. On the event side, the stimulus can be uninterpretable or not sensed at all because it is too degraded (either optically or aurally distorted), too faint (too dim or too soft), or too brief (e.g., presented for 2 milliseconds). (The preceding are examples of an absolute threshold, a concept in psychophysical scaling.) Alternatively, the observer can be the cause of the unconscious processing. A person can be outright unconscious (e.g., asleep or under anesthesia), unaware because of concurrent attentional demands, or suffer from a neurological [Page 752]condition that precludes conscious perception (e.g., blindsight, discussed below).

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