Background:

In the DRM paradigm participants are presented with lists of words (e.g. bed, rest, nap, etc.) in which all the words are related to a non-presented critical lure (e.g. sleep). Despite the fact that it was never explicitly presented, people falsely recognize and recall the critical lure at very high rates.

One way of understanding this is to assume that, although the critical lure was never explicitly presented to subjects, that it nonetheless gets implicitly presented to them in the form of a thought or association they make at time of study.  In other words, you're listening to the words, bed, rest, nap...and the word sleep suddenly pops into your mind.  Legendary memory psychologist Ben Underwood called such responses, Implicit Associative Responses, and used the concept to explain a number of memory phenomenon such as the word frequency effect.  Since Roediger and McDermott published their paper on false memories in 1995 a number of people have suggested that implicit associative responses may underlie false memories.

An alternative account of false memories is provided by Fuzzy Trace Theory.  Fuzzy Trace Theory holds that processing information leads to the parallel extraction of verbatim and gist traces.  Verbatim traces represent the surface form of the item that was presented, while gist traces represent overall patterns and meanings.  According to FTT, false memories in the DRM paradigm happen because (1) people fail to recall the verbatim trace, (2) they do recall the gist trace and (3) the critical lure matches the gist trace quite well, thank you very much.

Finally, a third account of false memories is provided by the Activation Monitoring Account.  The activation monitoring account proposes that activation spreads from the studied item to items that are related to it.  In the DRM paradigm, all the items are related to the critical lure, so the critical lure becomes highly activated, but (and this is important) not necessarily consciously activated.  At time of test, this high level of activation makes the critical lure seem quite familiar.  That's where the monitoring part comes in.  When the item seems familiar, subjects are basically presented with a source monitoring task (e.g. Did I hear the word or just think it?).

To address whether IARs occur and what effect they have on false memories, the authors had subjects overtly rehearse the lists as they were studying them.  Here we go!

Methods

Study Lists.  They started off with 16 DRM lists of 15 items each. Each subject studied 8 of these lists and the other 8 lists were used to generate unrelated distractors.  The particular lists that were studied were counterbalanced across subjects.  The lists were presented to subjects one word at a time on a computer screen.  For some subjects the words were presented at a rate of one word every two seconds and for others they were presented at a rate of one word every five seconds.

Study Instructions.  Half of the subjects were told to rehearse the words silently (i.e silent rehearsal) and half were told to rehearse the words outloud (i.e. overt rehearsal).  In the overt rehearsal condition subjects were told to say any word that came to mind while studying the list.

Testing.  Subjects either took a free recall test or a recognition test. The recognition test included three words from each studied list (24 words), the critical lure from each studied list (8 words), three words from each non-studied list (24 words), and the critical lure from each non-studied list (8 items).  On the recognition test subjects also made remember/know judgments.

The Occurence of False Recall and False Recognition?  False recall was pretty common, occurring close to 30% of the time on average.  False recall was not significantly influenced by whether overt or silent rehearsal was used.  Nor was false recall influenced by presentation rate. Corrected recognition of the presented items was higher with overt rehearsal and for the longer presentation duration,but neither of these influenced corrected recognition of the critical lures.

Do People Spontaneously Mention the Critical Lure During Study?  Yes, almost everyone in the overt rehearsal condition mentioned at least one critical lure and on average, people in the overt rehearsal condition mentioned about half the critical lures during study.

Did Rehearsing the Word at Study Influence False Memories?  To look at this they first collapsed accross subjects and used the individual critical lure of each individual subject as the level of analysis. They then calculated the probability that an item was recalled (or recognized, or received a remember judgment) given that it was rehearsed however many times (0,1,2, etc.).  Rehearsing a word at study led to more false recall, but did not increase false recognition or false remember judgments.  In a second analysis they looked at participants who both rehearsed and failed to rehearse at lease one critical lure. They then compared the probability of having a false memory for the rehearsed vs. unrehearsed items.  The same pattern of results emerged.

So to recap, here are the major results:

• People do spontaneously mention the critical lure while studying DRM lists.  In fact, the vast majority of subjects spontaneously mentioned at least one critical lure, and on average subjects mentioned half the critical lures.
• Spontaneous mention of the critical lure during study made it more likely that a subject would falsely recall the critical lure at time of test.  But false recall still occurred for a large proportion of critical lures that were not overtly rehearsed.
• Spontaneous mention of the critical lure during study was unrelated to false recognition or to false remember judgments.