1. Colour Discrimination Task
Exogenously Controlled Attention Does Not Inevitably Engage Awareness
C. Arnold1, J. Kinsella1, C. Heywood1 & R. Kentridge1
1Department of Psychology, University of Durham
Introduction
A stimulus can be the subject of endogenously controlled attentional biasing without reaching awareness.[1-3]
However, exogenous attention may be linked more closely with consciousness and more likely to lead to awareness. [4,5] .
This study aimed to investigate whether exogenous attention is sufficient for awareness.
Glossary
Attention – Selective biasing of neural processing of a region of space, object or feature (can facilitate or inhibit).
Congruency – Prime the same (congruent) or different (incongruent) colour as mask.
Consciousness/Awareness – Used interchangeably here to refer to the ability to report the memory of sufficient visual experience for stimulus detection.
Endogenous – Top-down, ‘voluntary’ shift of focus of attention.
Exogenous – Bottom-up, ‘involuntary’ capture of focus of attention.
ISI (Interstimulus Interval) – Time between offset and onset of two stimuli.
2. Method
Colour Discrimination Task
An exogenous cue was presented at one of 2 locations, above or below fixation, shortly followed by two different-coloured primes at both locations and then two identical annuli (meta-contrast masks).
Participants were not informed of the existence of the primes.
Participants (n = 13) made speeded discriminations of the colour of the 2 annuli targets/masks (1080 trials).
Prime Detection Task
Participants were then informed of primes’ existence and performed a detection task to test whether the primes reached visual awareness.
Trials were presented in sequential pairs, one with and one without primes (1200 pairs of trials).
Participants (n = 13) were asked to discriminate which trial in each pair had primes present.
Fixation
Cue: 54ms
ISI: 87/142/348ms
Primes: 33ms
ISI: 22ms
Masks:
Until Response
Fixation
Cue: 54ms
ISI: 87/142/348ms
Primes/No Primes: 33ms
ISI: 22ms
Masks:
1000ms
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3. Results
Prime Detection Task
Colour Discrimination Task
Mean accuracy (% +/- 95% confidence binomials) 20 40 60 80
100 * CE EK KF AD AM CC DS JA LM PM PT TM
Participant
141
196
402
Cue-Prime Stimulus Onset Asynchrony (ms)
Mean reaction time (ms +/- 1SE) *
300
350
400
450
500
Congruent
Incongruent
Detection data were analysed first to exclude participants able to detect the primes’ presence above chance.
One participant was excluded due to excessive eye movements.
All Trials (1200 pairs)
AD discriminated the primes’ presence significantly above chance (61%, p<.001).
All other participants p>.05 (maximum accuracy: TM, 53%, p=.078). AM CC CE DS EK JA KF LM PM PT TM
Mean accuracy (% +/- 95% confidence binomials) 20 40 60 80
100 *
Participant
Congruent
Incongruent
JA and TM discriminated incongruent primes’ presence different to chance
(p=.015 and p=.058).
All other participants p>.05 (maximum accuracy: EK incongruent, 53%, p=.149).
Trials split by cued-prime’s congruency (600 pairs each)
Only participants who could not detect the primes’ presence in the prime detection task were included in the colour discrimination analyses (n = 9).
Reaction times (RT) were faster when the cued prime was congruent (M=428ms) than incongruent (M=434ms), p=.006.
More errors when cued prime was incongruent (M=13.89) than congruent (M=12.67), but p=.433.
RTs were slower at 141ms SOA (M=441ms) than 196ms (M=427ms, p=.003) or 402ms SOAs (M=424ms, p=.042). No interaction between cue congruency and SOA (p=.326).
AD, JA and TM excluded from further analyses.
4. Conclusions
A stimulus can be the focus of selective, exogenously-controlled attentional biasing without necessarily reaching awareness - exogenous attention is not sufficient for awareness. This dissociation was demonstrated even in the absence of target detection - a more sensitive measure of visual awareness than target identification, used in some studies.
Attention and awareness are distinct processes and evidence of attention should not be assumed to be evidence of consciousness. The neural correlates of consciousness should not be confounded with the neural correlates of attention.
Future research should investigate what mechanisms modulate whether an attended stimulus reaches awareness or not.
References: [1] Kentridge, R., Heywood, C. & Weiskrantz, L. (1999). Attention without awareness in blindsight. Proceedings of the Royal Society London B, 266, [2] Kentridge, R., Heywood, C. & Weiskrantz, L. (2004). Spatial attention speeds discrimination without awareness in blindsight. Neuropsychologia, 42, [3] Kentridge, R., Nijboer, T. & Heywood, C. (2008). Attended but unseen: Visual attention is not sufficient for awareness. Neuropsychologia, 46, [4] Chica, A., Lasaponara, S., Lupianez, J., Doricchi, F. & Bartolomeo, P. (2010). Exogenous attention can capture perceptual consciousness: ERP and behavioural evidence. NeuroImage, 51, [5] Chica, A., Lasaponara, S., Chanes, L., Valero-Cabré, A., Doricchi, F., Lupianez, J. & Bartolomeo, P. (2011). Spatial attention and conscious perception: the role of endogenous and exogenous orienting. Attention, Perception and Psychophysics, 73,