بررسی حافظه کاذب در وظایف ضمنی ادراکی
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|32878||2006||21 صفحه PDF||سفارش دهید||محاسبه نشده|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Acta Psychologica, Volume 123, Issue 3, November 2006, Pages 240–260
Reports of critical lure priming in perceptual implicit tasks [e.g., McKone, E., & Murphy, B. (2000). Implicit false memory: Effects of modality and multiple study presentations on long-lived semantic priming. Journal of Memory and Language, 43, 89–109] using the Deese–Roediger–McDermott [Roediger, H. L., III, & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 803–814] procedure have suggested availability of the lexical form of lure items at study. Three experiments were conducted to further explore “false” implicit priming in perceptual tests. In Experiments 1 and 3, implicit and explicit stem completion tests were given in the DRM procedure with semantic lists; in Experiment 2, a graphemic response test was used in a similar design. For all experiments, explicit instructions resulted in reliable false memory, while implicit instructions resulted in priming for list items and no priming for lure items. Priming for lure items was evident for “test-aware” subjects only in Experiment 1 and in a combined analysis for all three experiments. These results establish boundary conditions for priming for critical lures and indicate that access to the lexical form of critical lures may not occur under incidental learning conditions when strong controls against explicit retrieval are implemented.
Findings of experimentally induced false memories have been frequently reported in recent studies. Many of these studies have utilized a paradigm originally developed by Deese (1959) and recently popularized by Roediger and McDermott (1995). In these experiments subjects are shown or read a list of words (e.g., dream, bed, blanket, etc.) that are linked by a conceptual theme word (e.g., sleep) that is not presented. Subjects commonly exhibit rates of false memories for the theme word (also called a critical lure) in tests of recall or recognition that are similar to rates of accurate recall or recognition for the list items that were presented ( Roediger & McDermott, 1995). This method is now known as the DRM procedure. In attempts to understand how these false memories are created, researchers have investigated several variables that attenuate or enhance false memories as compared to true memories. For example, semantic study tasks with levels of processing manipulations increase both accurate memory for list items and false memory for lure items (Coane and McBride, 2002 and Rhodes and Anastasi, 2000). This finding is not surprising, because the semantic study tasks are likely to strengthen the conceptual link between the list items and the critical item making them more likely to be remembered (or falsely remembered for the critical item) in the test. A finding that is more surprising is the one reported by several researchers (Hancock et al., 2003, McDermott, 1997, McKone and Murphy, 2000, Tajika et al., 2005 and Tse and Neely, 2005) where implicit false memory was found in implicit tasks typically classified as perceptual in nature. In contrast with explicit memory tasks (such as recall and recognition), implicit tasks do not require intentional retrieval of studied items. Instead, subjects are asked to perform a task that involves studied items with no reference made to the study episode. Many implicit tasks have been classified as perceptual tasks, because the test cues involve a perceptual form of the studied items. For example, in a word stem completion task, three-letter word stems are provided as cues in the test for the subjects to complete with the first word they think of. In lexical decision, items are presented for speeded word/non-word judgments. Target (studied) item performance that exceeds baseline rates when the items have not been studied provides measurements of implicit memory in the tasks. Performance in perceptual implicit tasks (like stem completion and lexical decision where perceptually altered forms of the studied items are given as cues) tends to be affected by perceptual manipulations (e.g., change in study to test modality), but is less likely to be affected by conceptual manipulations (like level of processing). In addition, there should be little or no perceptual advantage for critical lure items (over other non-studied items) in perceptual implicit memory tests because they are linked to study items conceptually and are not seen in the study phase. Critical lures should only show priming effects in perceptual implicit tests if their lexical form is accessed when list items are studied. Findings of false memory in perceptual implicit tasks have important theoretical implications. Evidence of priming for lures could be interpreted as evidence for long-term semantic priming. Semantic priming refers to the facilitation target items receive when the prime is semantically related (e.g., responses to nurse are faster and more accurate when the prime is doctor relative to when the prime is an unrelated word like cat). Whereas repetition priming (i.e., facilitation for items previously presented) tends to be long lasting, semantic priming tends to be very short-lived, and tends not to last across intervening items ( Meyer, Schvaneveldt, & Ruddy, 1974). Semantic or associative priming is furthermore assumed to be automatic and does not require that the prime be consciously perceived (e.g., Lukatela & Turvey, 1994). In the standard presentation of DRM lists, when several items and extended periods of time occur between presentation of list items and the critical lure, semantic priming would not be expected to occur. Thus, results that indicate that the critical lure can be primed at long intervals would provide evidence that semantic priming may not be as short-lived as previously thought. Furthermore, findings of false memory in implicit tasks can provide a test of one of the theories currently proposed as an explanation for false memory effects observed in the DRM paradigm. Roediger, Balota, and Watson (2001) have proposed that false memory effects created in the DRM procedure are due to a combination of two processes. They suggest that false memories for critical lures occur because (a) the lures are elicited (either consciously or automatically) due to semantic activation when the associated list items are studied and (b) the lures are mistakenly identified as studied when subjects make source errors in the memory test. This combination of processes is the activation-source account of false memory. Tse and Neely (2005) propose that priming effects for critical lures in implicit memory tests provide a means of obtaining false memory only due to activation processes, because source processes should be absent in implicit tests due to the nature of implicit retrieval. They state that priming for lures in implicit tests should not be caused by source errors, because subjects are asked to complete the task without reference to the study episode. Therefore, the source of the responses is irrelevant. Using this logic, examinations of false implicit memory are examinations of false memory due to activation alone. The exception to this occurs when explicit retrieval is used in the implicit test (i.e., explicit contamination) and the source processes become important. Tse and Neely (2005) evaluated false implicit memory using a lexical decision task, where subjects were asked to make word/non-word judgments for various types of test items. Some of the test items corresponded to DRM list items presented in a prior study session. Other test items were critical lures from the previously presented DRM lists. Test items were also included (list and lure items) for DRM lists that had not been studied. In four experiments, Tse and Neely found a reaction time advantage for responses to lures that were associated with studied lists as compared to lures associated to non-studied lists. They argued that their finding of critical lure priming even when no studied items were included in the lexical decision task prior to the critical lure item (experiment 4) provides strong evidence that priming for the lure can occur in perceptual tasks. Although Tse and Neely (2005) found false implicit memory in lexical decisions, overall, studies of implicit false memory in lexical decision tasks have reported inconsistent results. Like Tse and Neely, Hancock et al. (2003) found significant priming for critical lures in lexical decision tasks in four experiments. However, the control items used by Hancock et al. may have artificially inflated estimates of critical lure priming. As argued by Tse and Neely, Hancock et al. may have used a critical lure comparison condition that did not produce appropriate baseline RTs (see Tse & Neely, 2005, for a discussion of this point). In addition, Meade, Watson, Balota, and Roediger (in preparation) found priming for critical lures in a lexical decision task only when the lures were presented early in the test session. When one or more intervening items were presented between the primes and the target, no priming for lures was found, indicating a rapid decay of priming effects. Finally, Zeelenberg and Pecher (2002) found no priming for lures in a lexical decision task in their four experiments. McKone (2004) reported similar results for a lexical decision task. Therefore, the studies that used lexical decision as a measure of implicit false memory have provided mixed results. Studies examining false implicit memory in word stem and fragment completion have provided more consistent results. In her study, McDermott (1997) examined false memory using the DRM paradigm with implicit word stem and fragment completion tests and an implicit word association test. Implicit word stem and fragment completion tests are typically classified as perceptual memory tests, because test cues include degraded forms of the words (three-letter stems or word fragments with letters replaced with dashes). In word association tasks, however, conceptually related items are presented as test cues. McDermott found significant false implicit memory for the critical lure items in the fragment completion and word association tests and a marginally significant false memory effect for the stem completion test, indicating that priming for the critical lures can occur in perceptual (as well as conceptual) implicit tasks. One possible explanation of McDermott’s (1997) findings of priming for the critical lures may be that subjects explicitly retrieved items in the implicit tests. As described above, explicit tests of memory (e.g., recognition, cued recall) typically result in false memory for the lures. If subjects noticed a connection between the test cues and the items they had previously studied, they may have attempted to recall those items and mistakenly retrieved the lures as they do in explicit tests of memory. In fact, subjects in McDermott’s study were given 12–20 s to respond to the test cues, potentially allowing enough time for explicit retrieval to take place. In their study, McKone and Murphy (2000) attempted to test the explicit contamination explanation of McDermott’s results for implicit word stem completion tasks. They conducted three experiments using the DRM and stronger controls for explicit contamination (speeded instructions and post-test questionnaires) to rule out explicit retrieval as an explanation of McDermott’s findings of false implicit memory. Even with stronger controls for explicit contamination, their findings were similar to that of McDermott’s: Significant priming for critical lures was found, providing additional evidence of false implicit memory in perceptual tests. Despite better controls for explicit contamination, McKone and Murphy’s (2000) results for implicit stem completion might still be caused by explicit retrieval by their subjects. For example, subjects were given a chance to rehearse the study items for 30 s before testing, thus making it more likely that subjects would notice a connection between test items and study items. In addition, subjects may have consciously rehearsed the critical lure, thus explicitly accessing the lexical form. Indeed, rehearsing the critical lure has been found to enhance later false recall (Seamon et al., 2002). Subjects were also given an implicit deadline to complete responses (i.e., they were told to spend 2 s on each test item), but no actual deadline was imposed and no timing prompt was given during testing to let subjects know when to move on to the next item. Tajika et al. (2005) reported results similar to those of McKone and Murphy (2000). With incidental study tasks, subjects exhibited lure priming in an implicit stem completion test equal to priming for list items. However, like McKone and Murphy’s results, Tajika et al.’s results may be due to explicit contamination in the implicit test and may not actually reflect priming. Their implicit test included stems from only 24 items: 12 list items, 4 critical lures, and 8 unstudied items. With so few unstudied items in the test, it is likely that subjects connected the study and test episodes and may have intentionally retrieved study items to complete the word stems. Previous studies have indicated that the proportion of related or studied items included in an implicit test can affect the probability that subjects engage in intentional retrieval strategies (e.g., Tse & Neely, 2005). Intentional retrieval of study items would also have brought to mind the critical lures, resulting in lure completion rates which are above the rates for unstudied items. Although Tajika et al. reported administering a post-test questionnaire to all their participants, as they did not report how it was worded it is difficult to assess whether such a questionnaire was effective in screening participants who engaged in intentional retrieval. In addition, Tajika et al. only included lures associated with studied lists in the test. Lure items may be unique in that they are items with a number of strongly associated items and baseline rates may be different for these items as compared to items in the study lists. Therefore, Tajika et al.’s unstudied completion rates (which did not include lures from unstudied lists) may not make an appropriate comparison for completion rates of lures associated with studied lists. A comparison of false implicit memory results from studies with word stem and fragment completion tasks and studies with lexical decision shows that more consistent priming effects for lures are reported for the completion tasks. However, the consistent results could be due to consistent explicit contamination in these completion tasks (lexical decision tasks are less likely than stem and fragment completion tests to be contaminated by explicit retrieval, because the task is timed and tends to be much easier for subjects to complete). Therefore, the current study was designed to further investigate false implicit memory effects found in perceptual completion tasks described above with stronger controls for explicit contamination compared to prior studies. Perceptual memory tests were used in an attempt to support and generalize findings of false implicit memory in perceptual tests reported by McDermott, 1997, McKone and Murphy, 2000 and Tajika et al., 2005, as these results might have been contaminated by explicit retrieval attempts. Two tests typically classified as perceptual tasks (word stem completion and graphemic cued response) were used with implicit and explicit instructions in the DRM paradigm. To examine and reduce possible explicit contamination in the implicit tests, several checks were included in the method of the experiments. First, a level of processing manipulation was employed at study in the first two experiments. Explicit memory tasks typically show an advantage for items studied in a semantic task over a graphemic task, while implicit tasks rarely result in significant levels of processing effects (Roediger & McDermott, 1993). In all experiments, participants encoded items under incidental learning instructions to reduce the probability of explicitly accessing the lexical form of the critical lure during rehearsal and to minimize the chances that subjects in the implicit test conditions would engage in intentional retrieval. In addition, a time limit per trial (2–3 s, depending on the task) was imposed in the implicit tests to discourage use of explicit strategies. Test cues also included a large number of unstudied items other than the critical lures (68% fillers in 2 and 3; 75% fillers in Experiment 3) to hide the nature of the implicit tests and to avoid potential strategic changes on the part of participants due to high relatedness proportion. Lastly, subjects received a post-test questionnaire to determine if they had used explicit retrieval and/or become aware of the connection to the study items in the implicit tests. Subjects who indicated that they had used an explicit retrieval strategy were eliminated from the analyses. Subjects were classified as “test-aware” if they reported in the post-test questionnaire that they recognized a connection between study and test items and as “test-unaware” if they did not. Richardson-Klavehn and Gardiner (1996) have suggested that subjects who are aware of the study-test connection in implicit memory tests may use different retrieval processes than those who remain unaware, even in the absence of intentional retrieval. The analyses were conducted with awareness included as a between-subjects factor to test this possibility in the current study.