'The minimal exposure duration required for reflective consciousness' (AsPredicted #27805)
Author(s) Renzo Lanfranco (University of Edinburgh) - Renzo.Lanfranco@ed.ac.uk Andres Canales-Johnson (University of Cambridge) - afc37@cam.ac.uk Axel Cleeremans (Université Libre de Bruxelles) - axcleer@ulb.ac.be Hugh Rabagliati (University of Edinburgh) - hugh.rabagliati@ed.ac.uk David Carmel (Victoria University of Wellington) - david.carmel@vuw.ac.nz
Pre-registered on 09/12/2019 05:10 PM (PT)
1) Have any data been collected for this study already? It's complicated. We have already collected some data but explain in Question 8 why readers may consider this a valid pre-registration nevertheless.
2) What's the main question being asked or hypothesis being tested in this study? Two ERPs have been related to consciousness. First, the visual awareness negativity (VAN) has been related to phenomenal consciousness. Second, the late positivity (LP) has been related to reflective consciousness. If this is the case, in a visual discrimination task there should be a minimal exposure duration required for LP to discriminate between aware and unaware images while there should not be one for VAN.
We ran an experiment using an LCD tachistoscope that can present visual stimuli for microseconds. In one experiment, we presented participants with images of faces (and their scrambled counterparts), one of each on each side of the screen, and of objects in the same fashion. We found that VAN responds to the subjective awareness rating of the participant even when there was no perceptual discrimination. We also found that LP can only discriminate between aware and unaware trials when the exposure duration was 4.3 milliseconds or higher.
Here, we are pre-registering the analyses we will run for a second experiment. In this new experiment, we used emotional facial expressions instead:
1. If VAN is related to phenomenal consciousness, it should not depend on the exposure duration of the stimulus, even if they are emotional faces.
2. If LP is related to reflective consciousness, it should require a minimal exposure duration to be able to discriminate between "aware" and "unaware" faces.
3. If emotional valence can facilitate reflective awareness, then LP amplitude should be higher for emotional than non-emotional faces once it can distinguish between "aware" and "unaware" trials.
3) Describe the key dependent variable(s) specifying how they will be measured. It is voltage measured with EEG electrodes. We have defined two ERPs of interest, which will be measured at two different topographic locations on the scalp. Both respond to consciousness-related aspects of visual processing.
There are also other dependent variables that are relevant but their results are not new: location sensitivity, emotion identification sensitivity, emotion decision criterion, metacognitive sensitivity, metacognitive bias, and perceptual awareness.
4) How many and which conditions will participants be assigned to? This particular experiment involved presenting emotional expressions (neutral or emotional - the latter could be fearful or happy) at three different exposure durations (1.7, 4.4, and 6.2 ms). Therefore, there were 6 conditions in a repeated-measures within subjects design.
5) Specify exactly which analyses you will conduct to examine the main question/hypothesis. This time, the main hypothesis is about VAN and LP and about what aspects of consciousness they mark. We will separate each trial by their perceptual awareness scale (PAS) subjective score. Trials with a PAS = 1 ("no experience") will be classified as the "unaware" trials while the PAS > 1 trials ("vague impression", "almost clear experience", "clear experience") will be classified as the "aware" trials. We will compare:
1) VAN mean voltage between aware and unaware trials for each face expression condition
2) The same as 1 but for LP.
6) Describe exactly how outliers will be defined and handled, and your precise rule(s) for excluding observations. Exclusion criteria:
1. Participants whose EEG signal required >10 channels to be interpolated
2. Participants who required >5% of trials to be rejected due to EEG artifacts.
7) How many observations will be collected or what will determine sample size? No need to justify decision, but be precise about exactly how the number will be determined. 40 participants were tested. 32 of them were included in the analysis. This is because 8 of them either presented >5% of rejected trials or >10 channels that needed interpolation.
8) Anything else you would like to pre-register? (e.g., secondary analyses, variables collected for exploratory purposes, unusual analyses planned?) Originally, these two experiments were ran with a completely different purpose. The objective was to measure with psychophysics the minimal exposure durations required for (1) perceptual discrimination and metacognitive sensitivity of faces and emotional expressions, and (2) neural markers of face and emotion processing (N170, EPN, and LPP).
Now, we thought about using the same experiments for a very different purpose. To use the PAS scores originally thought to measure metacognitive sensitivity in order to categorise trials as aware or unaware and look whether there is a minimal exposure duration of reflective consciousness.
