Yung-Chun Lin ( 林永雋 ） 2005/10/3

1. Merikle, P. M., Smilek, D., & Eastwood, J. D. (2001).Perception without awareness: Perspectives from Cognitive Psychology.Cognition, 79, 115-134. Yung-Chun Lin (林永雋） 2005/10/3

2. Background concept • Perception is not necessarily accompanied by an awareness of perceiving. • It challenges the idea that perception implies consciousness. • Perception • with awareness • without awareness

3. Purpose • To demonstrate that perception without awareness is valid. • A framework for classifying visual perception studies. • To examine the fact that perception without awareness can influence conscious experience.

4. Conceptual framework • Dimension 1: Experimental logic • To demonstrate a dissociation between two separate measurements • To contrast perception with and without awareness in one measurement (less frequently used) • Dimension 2: Control of awareness • By stimulus variation • By manipulation of subjects’ attention

5. 3 1 4 2

6. Cell 1: Example 1 • Sidis (1898) • Stimuli: cards printed with a single letter or digit. • Set an appropriate viewing distance. • Verbal report: Subjects did not see what was on the card. • Forced-choice guessing: Better than chance. • Conclusion: An evidence for perception without awareness.

7. Cell 1: Example 1 (cont.) • Reingold & Merikle (1990): An assumption behind any dissociation between measures to be interpreted as evidence • Observers' verbal reports of their conscious experiences were an exhaustive measure of all relevant conscious perceptual experiences. • Otherwise, the dissociation simply indicates that the two measures of perception were sensitive to different aspects of consciously perceived information.

8. Subjective v.s. Objective Measure • Subjective measure: Self-report • Objective measure: Forced-choice decision • Which one is more accurate than the other? • For summaries of discussions see Merikle & Reingold (1998); Reingold & Merikle (1990) • Do observers perceive stimuli even when both measures of awareness indicate that the observers are unaware of the stimuli? • Both measures lead to the same conclusion- “yes”.

9. Subjective 3 1 Objective 4 2 Subjective

10. Cell 1: Example 2 • Williams (1938) • Stimuli: A circle, a triangle, or a square that is near threshold. • Subjective measure: To name the first figure that enters your mind

11. Cell 1: Example 2 (cont.) • Report also whether • (a) they saw the figure clearly • (b) they saw something but were doubtful of their choice • (c) they saw nothing at all and the choice was a pure guess • Conclusion: Subliminal stimuli are effective in evoking a correct response.

12. Cell 1: More Examples • Early studies using subjective measures • Horizontal, vertical, and diagonal lines (e.g. Baker, 1937; Dunlap, 1900) • Circles, triangles, and squares (e.g. Miller, 1942; Williams, 1938) • Letters and digits (e.g. Sidis, 1898; Stroh, Shaw, & Washburn, 1908)

13. Cell 1: More Examples • Recent studies using subjective measures • The lexical status of letter strings (e.g. Forster & Davis, 1984; Forster & Veres, 1998) • The meanings of words (e.g. Cheesman & Merikle, 1986; Merikle, Joordens, & Stolz, 1995) • The emotions expressed in faces (e.g. Esteves, Dimberg, & Öhman, 1994; Esteves & Öhman, 1993)

14. Cell 1: More Examples &Summary • More recent studies using subjective measures • fMRI: Fearful faces lead to greater neural activity in the amygdala than happy faces (Whalen et al., 1998) • PET: Angry faces perceived without awareness lead to activation in the right amygdala but not the left amygdala (Morris, Öhman, & Dolan, 1998) • All the studies above show that the stimuli are perceived even when subjects report that they do not have conscious experience of perceiving.

15. Cell 1: Example 3 • Marcel (1974, 1983): Priming effect • Prime-target pairs • A sub-threshold stimulus precedes a supra-threshold target stimulus. • “nurse”-“doctor” faster than “butter”-”doctor” • Variant: Prime-mask(noise)-target

16. Cell 1: More Examples • Studies used Marcel’s method • Word-to-word (e.g. Balota, 1983; Dagenbach, Carr, & Wihelmsen, 1989; Fowler, Wolford, Slade, & Tassinary, 1981; Greenwald, Draine, & Abrams, 1996; Kemp-Wheeler & Hill, 1988) • Picture-to-word (McCauley, Parmelee, Sperber, & Carr, 1980) • Picture-to-picure (Bar & Biederman, 1998) • Event-related potentials (ERP) & fMRI: Brain areas associated with motor programming as well as sensory processing(Dehaene et al., 1998)

17. Cell 1: Summary • Compelling evidence : Visual stimuli are perceived, semantically analyzed, and responded to even when they are presented under stimulus conditions that make it difficult for observers to discriminate between alternative stimulus states.

18. Distribution of Attention • Display stimuli at a number of spatial locations and instruct the observers to focus their attention at just one location. • It is possible to make subjects • aware of the stimuli at the focus of attention • unaware of the stimuli at spatial locations outside the focus of attention. • More analogous with daily experience

19. Cell 2: Example 1 • Mack and Rock (1998): Inattentional blindness 1500ms 200ms 500ms

20. Cell 2: Example 1 (cont.) • 60% of the participants in these studies were ‘blind’ to the presentation of the word. • For those who appeared to be ‘blind’ • Forced-choice recognition: Choose 1 from 5 words • 47% (baseline: 20%) • Stem completion: First two English words that came to mind. (e.g. fla  flake, flash) • 36% (baseline: 4%) • Despite they claimed to be unaware of the unattended words, sufficient information was perceived to influence their subsequent performance.

21. Subjective v.s. Objective Measures • Subjective measures show that correct forced-choice performance can occur even when there is no awareness of perceiving. • Objective measures • may provide more conservative estimates. • may also lead to an underestimation of the influence of information perceived without awareness (Merikle & Reingold, 1998). • Self-reports of conscious experiences is preferred (cf. Chalmers, 1996; Merikle, 1992).

22. Contrast the two types of perception in one measurement • Assumption • Information perceived with awareness enables a perceiver to act intentionally on the world and to produce effects on the world (cf. Chalmers, 1996; Searle, 1992). • information perceived without awareness leads to more automatic reactions that cannot be controlled by the perceiver.

23. Cell 3: Example 1 • Debner and Jacoby (1994) • Stimuli: Word-mask, the interval between them was either 50ms or 150ms • Procedure • The first three letters of the word were presented again • Participants were told to complete the word stem with the first word that came to mind except the word that had just been presented

24. Cell 3: Example 1 (cont.) Smith and Merikle (1999) Also, the attended and unattended words influenced performance in opposite ways.

25. Cell 3 & 4: More Examples • Cell 3: • Jacoby & Whitehouse, 1989; Marcel, 1980; Merikle & Joordens, 1997a; Murphy & Zajonc, 1993 • Cell 4: • Merikle & Joordens, 1997b • Summary: • These are additional evidence that stimulus information is perceived even when there is no awareness of perceiving.

26. Functions of perception without awareness • How does information that is perceived without awareness influence conscious experience? • It biases what is perceived with awareness • It influences how stimuli perceived with awareness are consciously experienced

27. Functions of perception without awareness: Example 1 • McCormick (1997) • A cue was briefly presented to the left or right of a central fixation cross and followed 500 ms later by a target letter (i.e. X or O). • 15% same side, 85% opposite side • Aware of the cue  judge the opposite side better • Unaware of the cue  judge the same side better

28. Functions of perception without awareness: Example 2 • Danziger, Kingstone, & Rafal (1998) • Patients with visual neglect in the left visual field • Cues was always followed by the presentation of a single target stimulus (i.e. a white cross) at the location of one of the cues. • A cue presented to the neglected, left visual field would attract attention despite the fact that the patients were unaware of the cue.

29. Functions of perception without awareness: Example 3 • Dunlap (1900) • The Müller-Lyer illusion can be induced by stimuli that are of such a low intensity as to be imperceptible.

30. Functions of perception without awareness: Example 4 • Mattingley, Bradshaw, & Bradshaw (1995) • Patients with left visuospatial neglect to bisect horizontal line segments. • Biased toward the right • Add either inward or outward pointing angular lines at the left ends of the lines. • The way in which the patients bisected the lines was biased by the angular lines in the neglected left visual field.

31. Conclusion • The concept of perception without awareness has been shown to have a solid empirical basis. • An important direction for future research studies is to explore the ways in which stimulus information perceived without awareness influences conscious experience. • bias what stimuli are attended. • influence how attended stimuli are consciously experienced.

32. Conclusion • Also, to evaluate how any functional differences that are documented may be related to or mediated by different neural pathways. • E.g. Posner and Rothbart (1992) have made a distinction between a posterior attention network, which mediates the orientation of attention, and an anterior attention network, which mediates consciousness awareness of attended objects.