A check on the memory deficit hypothesis of obsessive-compulsive checking
Moritz S, Jacobsen D, Willemborg B, Jelinek L and Fricke S;
Commented by , 22 Aug 2005
Background
The memory deficit hypothesis is one of the major theories that have been proposed in recent years to explain the checking behaviour in patients with obsessive-compulsive disorder (OCD). There is, however, only limited evidence in favour of the hypothesis up to now.
Aims of the study
To assess whether patients with OCD in general, and with OCD, checking type, in particular, have problems with memory and/or meta-memory, when they are presented with a task consisting in learning and remembering verbal material.
Method
27 patients with OCD (including 17 patients with OCD, checking type) and 57 healthy participants were administered a source memory task and completed a recognition task, involving recognition of words that were presented during the learning task. In addition, participants were asked to rate the degree of confidence with which they recognized words, and to rate the degree of vividness with which they remembered the words.
Results
No differences were observed in either performance for overall memory (memory) or in confidence in memory or in vividness of recognition (meta-memory) between patients with OCD and controls.
Professor Pull's comments
Patients with OCD (in particular of the checking type), may attribute their checking behaviour to a deficit in memory. According to these patients, they check because they cannot remember (suggesting a deficit in memory), or they cannot "really" or "fully" remember, or they cannot “feel” (suggesting a deficit in meta-memory) having closed the door, having turned off the light or the stove, or having completed all the items of a form.
According to the memory deficit hypothesis, the checking compulsions observed in patients with OCD could be attempts to compensate for real or imagined forgetfulness. Studies on the link between checking and memory problems have, however, produced equivocal results. In particular, most studies have been unable to detect a general memory deficit in patients with OCD.
The present study did not find any differences in either memory or metamemory, between patients with OCD and healthy controls. The study uses state of the art methodology, and as such, the results provide an important argument against the validity of the memory deficit hypothesis of OCD.
The main limitation of the study is that it deals exclusively with verbal memory. According to a growing field of investigations, the checking observed in OCD may in fact be linked to an impairment in the processing of non-verbal information, concerning complex visual stimuli, in particular motor stimuli that involve the individual's own actions.
Another limitation of the study concerns the fact that it does not investigate organizational strategies in OCD. According to some investigators, alleged or real memory deficits might be linked to a deficit in the organization that is necessary to effectively complete a task.
Still another limitation of the study is that assesses only two indices of metamemory (confidence in remembering and vividness of recollection), not, however, other indices such as "feeling of knowing" or "feeling of doing".
Future studies on the memory and metamemory in OCD should investigate the memory of non-verbal, in particular motor stimuli, and explore indices of meta-mory that explore "feeling of knowing or doing". First results from recent studies in this new line of research have already yielded promising results.