Bottom-up and top-down effects of unconscious

Transcription

1 Bottom-up and top-down effects of unconscious processing Eva Van den Bussche & Bert Reynvoet SCAN /23/2011 Herhaling titel van presentatie 1

2 Overview Introduction Bottom-up: The depth of unconscious processing Top-down: Is consciousness necessary for cognitive control? A new paradigm General conclusions Pag. 2

3 Introduction Can unconsciously / subliminally 9 presented information influence our 17ms ## behaviour? 33ms Masked priming paradigm (Marcel, 480ms ## 1983) 6 Smaller than 5 Larger than Pag. 3

4 Introduction Masked priming paradigm Congruent condition Incongruent condition Prime 6 1 Target 9 9 Difference (RT_I - RT_C) = priming effect Both > 5 One <, one > 5 Faster RTs Slower RTs Pag. 4

5 Bottom-up Can unconsciously / subliminally presented information influence our behaviour? YES! BUT: how far does this bottom-up strength reach? How deep can unconscious stimuli be processed? Pag. 5

6 Bottom-up How deep can unconscious stimuli be processed? 2 classes of theories: Semantically (e.g. Dehaene et al., 1998) Non-semantically, but due to low-level Stimulus-Response (S-R) mappings (e.g. Damian, 2001; Kunde et al., 2003) Pag. 6

7 Bottom-up 1. Semantic account: Prime 61 Smaller Larger than 5! 5! Response = press right left Target 9 Larger than 5! Incongruent Congruent Slower faster RT! Response = press right Pag. 7

8 Bottom-up 2. Non-semantic account: Prime 61 Larger than 5! Target 9 Response = press LEFT right Response = press right Incongruent Congruent Slower faster RT! Pag. 8

9 Bottom-up BUT: formation of S-R links limited to: Expected stimuli (e.g. repeated primes, same format) Small number of stimuli (e.g. small sets, small categories) NO subliminal priming expected for: unexpected stimuli, large stimulus sets, large stimulus categories Pag. 9

10 Bottom-up However: - Subliminal priming for large stimulus sets, large categories (for a meta-analysis see Van den Bussche et al., 2009a, Psych Bull) - Subliminal priming for unexpected formats (Dell Acqua & Grainger, 1999; Van den Bussche et al., 2009b; Van den Bussche et al., under review) Pag. 10

11 Bottom-up Conclusion: Despite the limited bottom-up strength, unconscious stimuli can influence behavior and be processed up to a high semantic level! ~ consensus Pag. 11

12 Top-down But, can an unconscious stimulus modify unconscious processing by exerting topdown control? = heavily debated! Subliminal processing = a condition of information inaccessibility where bottom up activation is insufficient for global ignition (Dehaene et al., 2006, p.3) Pag. 12

13 Top-down Double prediction (GNW): 1. Unconscious processes are sensitive to conscious strategic and contextual influences 2. However, an unconscious stimulus itself cannot modify unconscious processing by exerting top-down control Pag. 13

14 Top-down 1. Unconscious processes are sensitive to conscious strategic and contextual influences Yes! Unconscious priming can be influenced by temporal attention (Naccache et al., 2002), spatial attention (Sumner et al., 2006) and strategies, such as target set (Greenwald et al., 2003) and target notation (Kunde et al., 2003) Pag. 14

15 Top-down Example: Kunde et al. (2003) Targets Primes Priming? 1, 4, 1, 4, Yes 1, 4, one, four, No one, four, 1, 4, No one, four, one, four, Yes Unconscious priming effects were dependent on the target notation (i.e. a conscious manipulation) Pag. 15

16 Top-down 2. However, an unconscious stimulus itself cannot modify unconscious processing by exerting top-down control??? Pag. 16

17 Top-down Our study (VDB et al., 2008, Con & Cog) Investigate the 2 predictions by manipulating the proportion (50-50, or 75-25) of Arabic numbers (e.g. 1) versus number words (e.g. one ): Consciously (target level): experiment 1 Unconsciously (prime level): experiment 2 All other task conditions were controlled Pag. 17

18 Top-down Congruent trial nine 33ms 33ms 7 #$#$#$ 300ms $#$#$# Smaller than 5 Larger than Pag. 18

19 Top-down Prim ming effect (ms) F(2,43) = 3.70, p =.03 F(2,44) = 0.22, p =.81 N = 15 N = 16 N = 15 N = 16 N = 16 25% Arabic targets 75% Arabic targets baseline 25% Arabic primes 75% Arabic primes Arabic primes Number word primes The conscious manipulation exerted top-down control on the priming effects, but the unconscious manipulation did not Pag. 19

20 Top-down 2. However, an unconscious stimulus itself cannot modify unconscious processing by exerting top-down control Yes! But Pag. 20

21 Top-down Is consciousness necessary for cognitive control? Yes: Ansorge et al., in press; Kunde, 2003; Merikle & Joordens, 1997; Nieuwenhuis et al., 2001; Van den Bussche et al., 2008 No: Bodner & Masson, 2001; Cohen et al., 2009; Hughes et al., 2009; Lau & Passingham, 2007; van Gaal et al., 2008; Pag. 21

22 Top-down Unconscious manipulations can NOT influence priming (Merikle & Joordens, 1997; Van den Bussche et al., 2008) An unconscious conflict can NOT induce conflict adaptation effects (Ansorge et al., in press; Kunde, 2003) Unconscious errors do NOT lead to posterror slowing (i.e. remedial action to prevent future errors) (Nieuwenhuis et al., 2001) Pag. 22

23 Top-down Unconscious manipulations can influence priming (Bodner & Masson, 2001) An unconscious conflict can induce conflict adaptation effects (van Gaal et al., 2010) Unconscious errors can lead to post-error slowing (Cohen et al., 2009) Unconscious information can act as a stop signal and urge subjects to interrupt their ongoing response to a task (Hughes et al., 2009; van Gaal et al., 2008) Unconscious information can influence task selection (Lau & Passingham, 2007) Pag. 23

24 Top-down Aforementioned studies suffer from critical problems: 1. Objective post-hoc awareness tests which are heavily debated 2. Visual strength of the stimuli always critically differed in the conscious and unconscious conditions 3. Different experimental paradigms difficult to compare Pag. 24

25 A new paradigm Our current aim: investigate whether consciousness is needed for cognitive control, but using a paradigm which avoids the problems demonstrated for previous studies! How? Pag. 25

26 A new paradigm Design: #$#$#$ RED $#$#$# &&&&& How certain are you that the colour word presented before the target was "RED" or "BLUE"? Target classification Trials are divided based on prime awareness task in conscious and unconscious trials Pag. 26

27 A new paradigm Advantages: 1. Trial-based assessment method 2. Visual strength identical in conscious and unconscious conditions 3. Paradigm can be used to examine a wide array of top-down effects (priming, conflict adaptation, ) Pag. 27

28 A new paradigm Disadvantages: 1. Requires many participants 2. Requires many trials (exclusion of uncertain trials) 3. Takes some time to master Pag. 28

29 A new paradigm Does it work? - Took many pilot studies to get it right (masks, prime duration, PAS-scale, number of trials, etc.) - First finished study just completed! Pag. 29

30 A new paradigm Design (320 trials): 480 ms 40 ms 27 ms 2000 ms $#$#$# RED $#$#$# &&&&& a (RED) p (BLUE) How certain are you that the colour word RED or BLUE was presented before the coloured symbols? 1.I am certain that I saw the colour word RED: press button "1 2.I think I saw the colour word RED, but I am not certain: press button "2 3.I did not see the colour word: press button "3 4.I think I saw the colour word BLUE: press button "4 5.I am certain that I saw the colour word BLUE: press button "5" Press the spacebar when you're ready to start the next trial. Place your fingers on buttons "a" and "p" again to be able to categorize the coloured symbols as fast as possible If the symbols are red: press "a" If the symbols are blue: press "p" SPACE Pag. 30

31 A new paradigm Results - N=60 24 excluded - Conscious trials (on average 99) = subjects correctly identified the primes and were 100% certain - Semi-conscious trials (on average 97) = subjects correctly identified the primes but were not certain - Unconscious trials (on average 61) = subjects reported not being able to identify the prime Pag. 31

32 A new paradigm Results: - Repeated measures with condition (conscious, semi-conscious or unconscious) and congruency (congruent or incongruent) as within-subject factors - Significant interaction between condition and congruency (F(2,33)= 15.81, p<.001) Pag. 32

33 A new paradigm 146ms*** 33ms* 24ms* Pag. 33

34 A new paradigm Does it work? - Yes! - Next step: examine the effect of topdown manipulations on the conscious VS unconscious trials Pag. 34

35 General conclusions Unconscious information - Can influence our behavior - Has limited bottom-up strength, but is still able to be processed up to a high, semantic level - Seems to be able to exert top-down control as well, although further research using an improved paradigm is needed Pag. 35

36 Contact Eva Van den Bussche Vrije Universiteit Brussel Department of Psychology Pleinlaan Brussels Belgium Eva.Van.den.Bussche@vub.ac.be Pag. 36