Forgetting in the no-think paradigm: Interference or inhibition?

Abstract

When participants, after learning a set of paired associates (e.g., "plane-doctor"), are repeatedly asked to suppress the target ("doctor") upon presentation of its cue ("plane"), such suppression trials can cause later forgetting of the target information. Whereas the original account attributed such forgetting to inhibition of the suppressed memory (1), Tomlinson et al. (2) suggest that forgetting may arise as a result of interference at test. Tomlinson et al. argue that, although in opposition to task instructions, participants occasionally may sample the target during no-think training and then learn to associate this memory with the no-think response (i.e., "sitting quietly"). Later, at test, the newly learned association interferes with recovery of the target information, causing the observed forgetting.Tomlinson et al.'s account is in the tradition of global computational memory models, which assume that recall of memory traces occurs by means of a two-stage process, which includes initial sampling and a subsequent recovery stage. Although to date such memory models have placed interference effects alone at the sampling stage of recall, Tomlinson et al. allow interference to affect the recovery process as well. Assuming that the sampled memory of a target is an incomplete representation (e.g., "d_ct_r"), they suggest that, during no-think trials, participants learn to associate the sampled target memory with the no-think response, which then at test compete for conscious recall. Doing so, Tomlinson et al. generalize existing global memory models and provide an elegant, noninhibitory account of forgetting over a wide range of recall conditions. A crucial assumption of Tomlinson et al.'s interference account is that new associations are built up during no-think trials, suggesting an increase in memory-related activity over repeated suppression trials. This suggestion contrasts with findings from neurocognitive studies reporting evidence for a down-regulation of memory-related neural activity during no-think trials (3, 4). When no-think trials are compared with a no-recall fixation baseline (3), fMRI results show that suppression trials lead to decreases in hippocampal activity. Similarly, a recent eventrelated potentials study (4) reported a reduction in cued-recall positivity with increasing no-think trial repetitions that predicted the amount of no-think forgetting. Remarkably, memory-related neural activity was already down-regulated in anticipation of a suppression trial, suggesting a role of anticipation for no-think forgetting (5).When different measures of neural activity (fMRI, EEG) are used, the results from the two neurocognitive studies converge on the view that retrieval success is voluntarily down-regulated during suppression trials. These results support the inhibition view of no-think forgetting but appear incompatible with the suggested interference account, according to which memoryrelated activities during suppression trials should increase rather than decrease.

Emotions shape memory suppression in trait anxiety

“…Negative scenes coming from the no-think procedure showed enhanced accuracy and shorter reaction times in the high compared to the low trait anxiety group. One should note that these results are unlikely to be related to the use of different strategies causing possible interferences during the no-think phase because participants were strongly discouraged from generating other memory associations while viewing the word-cues ( Bäuml and Hanslmayr, 2010 ; van Schie et al, 2013 ).…”

Blocking of irrelevant memories by posterior alpha activity boosts memory encoding

“…It is debated to what extend impaired memory encoding is explained by interference or inhibition [Bauml and Hanslmayr, ]. It could be argued that reduced memory encoding after the “No‐Remember” cue is explained by a strategy in which subjects deliberately engage in other mental processes to prevent encoding.…”

“…This implies that efficient memory functioning involves not only successful remembering but also successful forgetting [Johnson, 1994;Van Hooff et al, 2009]. The mechanisms controlling memory encoding have been investigated by directed forgetting, think/no-think or cued encoding paradigms using various kinds of brain imaging techniques [Anderson and Green, 2001;Anderson et al, 2004;Bauml and Hanslmayr, 2010;Daselaar et al, 2004;Depue et al, 2007;Fawcett and Taylor, 2008;Freunberger et al, 2009;Hanslmayr et al, 2009aHanslmayr et al, , 2010Norby et al, 2010;Wagner and Davachi, 2001;Wylie et al, 2008]. From these studies, it is clear that the human memory system engages and disengages various brain regions in order to facilitate and prevent memory encoding.…”

Moderate levels of activation lead to forgetting in the think/no-think paradigm

“… 13 For additional discussion of the idea that forgetting could be caused by interference from newly learned associations (as opposed to weakening of no-think memories) see Tomlinson et al (2009), Bauml & Hanslmayr (2010), and Huber et al (2010). …”