Methodological considerations

The goal of the research described in this chapter is to assess whether forcing witnesses to fabricate fictitious items and events leads them to develop false memories of having witnessed these knowingly fabricated events. To answer this question, we have designed all of our studies with the following methodological considerations in mind. In this chapter, we restrict our review to studies conducted with adult participants who meet these methodological requirements.

Ensuring testimony is forced rather than freely provided

The goal of forced fabrication studies is to mimic forensic situations where witnesses are pressed to fabricate testimony they would not have provided had they not been pressured to do so (for related paradigms where participants sometimes voluntarily respond to false-event questions, see Pezdek, Sperry, & Owens, 2007; Pezdek, Lam, & Sperry, 2009; Combos, Pezdek, & Haymond, 2011). To that end, participants are asked questions about objects and events that they clearly never witnessed and that are not readily guessed. Although the resistance participants display when pressed to provide fabricated responses provides compelling evidence that they are being “forced”, we have also sought more direct evidence. To this end, in two of our forced fabrication studies (Ackil & Zaragoza, 1998; Zaragoza et al., 2001), we included a second group of participants (the “free” group) who were instructed that they should respond “don’t know” if they did not know the answer to a question posed by the interviewer, and should refrain from guessing. In both studies, none of the participants in the free group spontaneously provided answers to any of the false-event questions, thus verifying that participants do not answer these questions unless forced to do so.

Assessing the extent to which false memories are caused by the forced fabrication interview

Because our central concern is determining whether forced fabrication leads to memory distortions, an important methodological issue is isolating memory errors that result from the suggestive interview from memory errors that might result from other causes (e.g., spontaneous inference). To do so requires assessing the extent to which control participants, who were never asked to fabricate these events, might claim to remember witnessing the fabricated events on the final memory test (i.e., to establish the base rate of assenting to the fabricated events). If forced fabrication leads to false memory, participants’ claims of having witnessed the fabricated events should reliably exceed the base rate of these false claims, and this is the measure of false memory we employed in all of the studies reviewed here. Across studies, we have consistently found that the base rate of false assents to the fabricated events is low (on yes/no recognition tests typically 10% or less; on measures of free recall, it was consistently at floor), thus providing further evidence that participants witnessing these events do not infer the fabricated events spontaneously. Rather, these false memory errors are a direct consequence of the forced fabrication interview.

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