Consciousness and Cognition 21 (2012) 1573–1574

Contents lists available at SciVerse ScienceDirect

Consciousness and Cognition journal homepage: www.elsevier.com/locate/concog

Reply

Response to Desender & Van den Bussche: On the absence of a relationship between discriminability and priming q Jolien C. Francken a, Simon van Gaal a,b, Floris P. de Lange a,⇑ a b

Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behavior, Nijmegen, Netherlands INSERM/CEA Cognitive Neuroimaging Unit, Gif-sur-Yvette, France

In their recent letter Desender and Van den Bussche (D&B) (2012) raise several issues with respect to our recent study (Francken, Gaal, et al., 2011), in which we describe a lack of relationship between how well a prime is perceived and its ability to influence behavior (i.e., priming). Here, we will shortly reply to these points. D&B argue that our results have no bearing on conscious vs. unconscious priming, since prime discriminability was above chance in both conditions. We fully agree with D&B that our study does not compare fully conscious with fully unconscious stimuli (as is also explicitly stated in the manuscript, where we speak about poorly discriminable and well discriminable primes). Nevertheless, there was a sizeable difference in discriminability between the low-visible and high-visible primes. If discriminability were relevant for priming, one would therefore expect the priming effects to differ between the conditions. Conversely, we found no differences in priming between low-visible and high-visible primes. Also, in spite of the large individual range of discriminability differences between metacontrast-masked and pseudomasked primes, there was no relationship between discriminability and priming effects, as visible from both a median-split analysis and correlation analysis (all p > 0.30). The second issue deals with the signal strength of the prime. According to D&B, signal strength was higher when primes were pseudomasked than metacontrast-masked, since they ‘‘critically differed in masking the direction of the prime’’. However, signal strength of the prime was defined in our study as the amount of priming it can elicit, not its visibility. Indeed, our study, as well as others (Vorberg, Mattler, et al., 2003) indicate that signal strength is dissociated from its visibility. Lastly, D&B describe their attempt to deal with the issues they raised, by ‘‘displaying the prime for an intermediate duration (40 ms), so that primes were unconscious on some trials and conscious on others’’. While we agree that this approach controls for potential stimulus differences, we would like to make a cautionary remark with respect to such a design. We believe that such a design may not allow for conclusive judgments about the role of awareness in priming per se. Namely, when not experimentally controlling awareness (e.g., by changing the masking parameters), but by relying on post hoc trial sorting, there are a number of (non-controlled) factors that may contribute to the effect. For example, it is well-known that there is an intimate relationship between awareness and attention (Dehaene & Changeux, 2011), which may well explain the larger priming effect for aware items in the study by D&B: on some trials, a subject’s attentional state was higher, leading to both stronger awareness and more priming. Also learning effects over time (subjects learn to ‘see’ the shape, therefore increasing awareness, while at the same time becoming more trained on the task, leading to larger prime congruency effects) may provide a partial explanation of the effect. In sum, we think that D&B raise some very important issues and we fully agree with D&B that ‘‘efforts should be made to compare conscious with truly unconscious conditions’’. The solution however, may not be to rely on post hoc sorting of data, but rather rigorous experimental control over the participant’s state of awareness.

q Reply to the Commentaries on Desender, K. & Van den Bussche, E. (2012). The magnitude of priming effects is not independent of prime awareness. Reply to Francken, van Gaal, & de Lange (2011). Consciousness and Cognition, 21, 1571–1572. ⇑ Corresponding author. Address: Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behavior, P.O. Box 9101, 6500 HB, Nijmegen, Netherlands. Fax: +31 24 36 10652. E-mail address: fl[email protected] (F.P. de Lange).

1053-8100/$ - see front matter Ó 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.concog.2012.04.005

1574

J.C. Francken et al. / Consciousness and Cognition 21 (2012) 1573–1574

References Dehaene, S., & Changeux, J. P. (2011). Experimental and theoretical approaches to conscious processing. Neuron, 70, 200–227. Desender, K., & Van den Bussche, E. (2012). The magnitude of priming effects is not independent of prime awareness. Reply to Francken, van Gaal, & de Lange (2011). Consciousness and Cognition, 21(3), 1571–1572. Francken, J. C., Gaal, S., et al (2011). Immediate and long-term priming effects are independent of prime awareness. Consciousness and Cognition, 20, 1793–1800. Vorberg, D., Mattler, U., et al (2003). Different time courses for visual perception and action priming. Proceedings of the National Academy of Sciences of the United States of America, 100, 6275–6280.