While initially subject to debate, meta-analyses have shown that eye movement desensitization and reprocessing (EMDR) is effective in the treatment of posttraumatic stress disorder (PTSD). Earlier studies showed that eye movements during retrieval of emotional memories reduce their vividness and emotionality, which may be due to both tasks competing for limited working memory (WM) resources. This study examined whether another secondary task that taxes WM has beneficial effects, and whether the stronger the taxing, the stronger the reductions in vividness/adversity. A reaction time (RT) paradigm showed that counting backwards requires WM resources, and that more complex counting is more demanding than simple counting. Relative to a retrieval-only condition, counting during retrieval of emotional memories reduced vividness and emotionality during later recall of these memories. However, the counting conditions did not differ in the magnitude of this reduction, and did not show the predicted dose-response relationship. Implications for a working-memory explanation of EMDR and for clinical practice are discussed.

Posttraumatic stress disorder (PTSD) is effectively treated with eye movement desensitization and reprocessing (EMDR) with patients making eye movements during recall of traumatic memories. Many therapists have replaced eye movements with bilateral beeps, but there are no data on the effects of beeps. Experimental studies suggest that eye movements may be beneficial because they tax working memory, especially the central executive component, but the presence/degree of taxation has not been assessed directly. Using discrimination Reaction Time (RT) tasks, we found that eye movements slow down RTs to auditive cues (experiment I), but binaural beeps do not slow down RTs to visual cues (experiment II). In an arguably more sensitive "Random Interval Repetition" task using tactile stimulation, working memory taxation of beeps and eye movements were directly compared. RTs slowed down during beeps, but the effects were much stronger for eye movements (experiment III). The same pattern was observed in a memory experiment with healthy volunteers (experiment IV): vividness of negative memories was reduced after both beeps and eye movements, but effects were larger for eye movements. Findings support a working memory account of EMDR and suggest that effects of beeps on negative memories are inferior to those of eye movements.

Patients with obsessive-compulsive disorder respond to clinical uncertainty with perseverative checking, which, ironically, enhances uncertainty. However, patients also display general subclinical uncertainty, which may tempt vulnerable individuals to seek reassurance by perseveration in response to mild uncertainty that is superimposed on general uncertainty. An experimental eye-tracking paradigm was developed to investigate whether mild uncertainty indeed induces checking behavior in people with high obsessive-compulsive tendencies (OC+, n = 34), compared to people with low obsessive-compulsive tendencies (OC–, n = 31). Participants were presented 50 visual search displays, and they indicated whether a target was “present” or “absent.” Decisions about target presence induced little uncertainty, but decisions about its absence were more ambiguous, because participants relied on not having overlooked the target. Results revealed no differences on target-present trials. However, in target-absent trials, OC+ participants searched longer and used more fixations. Thus, even in mildly uncertain situations, individuals with subclinical obsessive-compulsive disorder respond with more checking behavior, which has implications for treatment.

According to the Proust phenomenon, olfactory memory triggers are more evocative than other-modality triggers resulting in more emotional and detailed memories. An experimental paradigm was used to investigate this in aversive memories, similar to those experienced by patients with posttraumatic stress disorder. Seventy healthy participants watched an aversive film, while simultaneously being exposed to olfactory, auditory and visual triggers, which were matched on intensity, valence, arousal and salience. During a second session one week later, participants were randomly exposed to one of the three triggers, and asked to think back about the film and to rate the resulting memory. Results revealed that odour-evoked memories of aversive events were more detailed, unpleasant and arousing than memories evoked by auditory, but not visual, triggers.

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