Review of 'Explicit Memory for Unattended Words: The Importance of Being in the "No"'

Typically, young adults who are asked to ignore distracting information (i.e. inhibit it), are quite capable of doing exactly that.  They tend to perform well on the attended task and show little to no memory for items that are presented as distraction (which they were asked to ignore).  This has usually been taken as evidence that when tested implicitly for encoding distractors, young adults under normal conditions demonstrate excellent ability to filter these out and prevent access to working memory (i.e. Gazzaley et al., 2008; Lustig, Hasher, & Zacks, 2007).

The upshot is that young adults supposedly are more able to focus on what matters (the task at hand), but may not have access to the information they were asked to block out since it was supposedly filtered out before it could be incorporated into a memory trace.

This is where things get interesting...  Hoffman et al., claim that in fact this type of information is indeed accessible - scientists just haven't been using sensitive enough measures to evoke it.  The group used a task developed by Rees et al., (1999) where words were superimposed on line drawings and participants were asked to respond every time a line drawing repeated (ignoring the words).  Rees et al., showed that young adults successfully ignored the words unless they were specifically asked to attend them.

From Rees et al., (1999)

From Hoffman et al., (2011)

Hoffman et al., (2011) used a refinement of this study by adding confidence ratings on top of pure recognition.  In other words, not only were participants being asked "do you recall seeing this word?", but "how confident (using a 4 point scale) are you about that response?"

As you can see (above) using this new measure, the authors managed to look within the "No" responses (at words that were supposedly inhibited) and show that people are more confident that novel words are actually new than words that previously appeared as distraction meaning that young adults do in fact have access to this information at some level.

This is quite an impressive finding.

The authors then go on to claim that this is explicit memory.  Here I think they may be overstating their claims a bit.  True, recognition of items is explicit and requires a conscious memory to make that judgement. However claiming that items that were consciously rejected but show what I would argue is an implicit difference using a confidence rating is another kettle of fish altogether.  What the authors have, is a replication of the previously described explicit findings, but within them an implicit difference.

In the inhibition and attention literature, this is a very significant finding as it demonstrates that previously inhibited information isn't lost, but may be accessed given the right circumstance - that said, I would argue that this information is almost certainly not explicit, and would probably be more akin to an implicit "gut feeling" than anything else.

Gazzaley, A., Clapp, W., Kelley, J., McEvoy, K., Knight, R. T., & D’Esposito, M. (2008). Age-related top-down suppression deficit in the early stages of cortical visual memory processing. Proceedings of the National Academy of Sciences of the United States of America, 105(35), 13122-6. doi:10.1073/pnas.0806074105

Hoffman, Y., Bein, O., & Maril, A. (2011). Explicit memory for unattended words: the importance of being in the “no”. Psychological science, 22(12), 1490-3. doi:10.1177/0956797611419674

Lustig, C., Hasher, L., & Zacks, R. T. (2007). Inhibitory Deficit Theory : Recent Developments in a “ New View .” Inhibition in cognition, (571), 145–162. American Psychological Association Washington, DC. Retrieved from http://www-personal.umich.edu/~clustig/Publications/chapters/LustigHasherZacks.pdf

Rees, G., Russell, C., Frith, C. D., & Driver, J. (1999). Inattentional blindness versus inattentional amnesia for fixated but ignored words. Science, 286(5449), 2504-2507. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10617465