Two techniques for investigating perception without awareness

Abstract

This note deals with the logic of recent experiments on perception without awareness. In these experiments, a stimulus is presented in such a way that some forcedchoice discrimination concerning that stimulus is at chance. Usually this involves use of a backward pattern mask. Evidence is then sought that, despite chance performance on the forced-choice discrimination (' 'lack of awareness"), processing of the stimulus is indicated in some other aspect of behavior.I shall use priming experiments as an example. The masked stimulus S, is immediately followed by a second, clearly visible, stimulus, S2. The question of interest is whether the identity of S, can influence response to S2' For example, S, might be a color word, and S2 an ink patch whose color the subject is to name as fast as possible. A Stroop effect (i.e., an effect of congruence or incongruence between S, and S2), occurring even when discriminations concerning S, were at chance, would be taken as evidence for perception without awareness. Experiments of this sort have looked at the effects of various relationships between S, and S2' using both words and pictures as stimuli.The evidence on whether such priming effects can be found is in fact quite mixed (for positive results see Balota,

Confidence and Accuracy of Near-Threshold Discrimination Responses

“…Some studies have contradicted this conclusion by reporting evidence of subliminal perception with stimuli presented below performance-based thresholds (e.g., Balota, 1983;Erdley & D'Agostino, 1988;Fowler, Wolford, Slade, & Tassinary, 1981, Experiments 5 and 6;Greenwald, Klinger, & Liu, 1989;Greenwald, Klinger, & Schuh, 1995;Marcel, 1983;Niedenthal, 1990;Snodgrass, Shevrin, & Kopka, 1993), but the evidence from such studies has generally been disputed because of demonstrated or suspected methodological problems-for example, insufficient trials used for threshold determination (e.g., Dosher, 1998;Duncan, 1985;Holender, 1986;Kunimoto, 1994;Merikle, 1982Merikle, , 1992Miller, 2000;Nolan & Caramazza, 1982;Van Selst & Merikle, 1993). Thus, it is still arguable which paradigms are capable of determining whether perception occurs when stimuli are presented below the threshold for a discriminative or presence-absence response.…”

Unconscious perception: A model-based approach to method and evidence

“…One straightforward possibility (cf. Duncan, 1985) is to simply use a forced-choice identification task (Cheesman & Merikle, 1984). But what about other indexes?…”

Recent models and findings in visual backward masking: A comparison, review, and update

“…For instance, the magnitude of backward masking is affected by perceptual grouping and segmentation (Caputo, 1998;Kurylo, 1997;Wolf, Chun, & Friedman-Hill, 1995) and by deployment ofselective visual attention (Enns & Di Lollo, 1997;Havig, Breitmeyer, & Brown, 1998;Michaels & Turvey, 1979;Ramachandran & Cobb, 1995;Shelley-Tremblay & Mack, 1999). Closely related, backward masking recently has been used to study visual awareness (Bachmann, 1997;Dennett, 1991;Klotz & Neumann, 1999;Klotz & Wolff, 1995;Neumann & Klotz, 1994) and its implications for the controversial field ofsubliminal perception (Duncan, 1985;Holender, 1986;Kihlstrom, 1987;Marcel, 1983). Finally, backward masking has been used to study certain clinical anomalies related to vision and brain function, such as amblyopia (Tytla & Steinbach, 1984), closed head injury (Mattson, Levin, & Breitmeyer, 1994), developmental dyslexia (Williams, LeCluyse, & Bologna, 1990;Williams, Molinet, & LeCluyse, 1989), mania (Green, Nuechterlein, & Mintz, 1994a, 1994b, and schizophrenia (Green, Nuechterlein, & Breitmeyer, 1997;Green, Nuechterlein, Breitmeyer, & Mintz, 1999;Green et aI., I994a, I994b;Merritt & Balogh, 1984;Saccuzzo & Schubert, 1981;Slaghuis & Bakker, 1995).…”