Efectos de la protección.

The extent to which conscious and unconscious processes contribute to direct and indirect associative memory tests has not been established with any certainty in the task dissociation research. The prim ary approach used to indicate a role for unconscious processes in memory for new associations is a functional dissociation between direct and indirect associative memory tests. As described in section 1.4.1.1, manipulation o f levels o f processing (Schacter & Graf, 1986a), retroactive and proactive interference (G raf & Schacter, 1987), attention at retrieval (Kinoshita,

1998), and changes in modality between study and test (Schacter & Graf, 1989), all dissociate associative prim ing from the conscious retrieval o f associative information.

However, the functional dissociation evidence is equivocal, because upon closer inspection, task factors, other than the experimentally manipulated variable(s), may differ between direct and indirect memory tests. Indeed, despite the fact that the series o f studies conducted by G raf and Schacter satisfy the conditions o f the retrieval intentionality criterion (Schacter, Bowers, & Booker, 1989), in that only the instructions at test were varied, it is evident that complex, spontaneous retrieval strategies can arise in the course o f performing m emory tests (e.g., Hauselt, 1998). Further, only limited inferences can be made when using a one-way function dissociation as the benchmark

1. Explicit-Implicit M emory and Ageing: Experimental W ork

for determining the extent to which processes represent independent bases for responding (Dunn & Kirsner, 1989; Jacoby, 1991; Reingold & Merikle, 1988, Chapter 2). These concerns are not recent, however, since they can be traced back to early studies that examined mem ory for new associations in organic amnesic patients (Schacter & Graf, 1986b).

There are four factors that suggest the associative priming o f words, at least in some instances, is mediated by conscious memory processes. First, associative word stem completion is sensitive to the levels o f processing encoding manipulation, which contrasts with the typical finding in perceptual item priming (but see. Brown & Mitchell, 1994). As discussed earlier, the most reliable demonstrations o f memory for new associations are produced by manipulations that instantiate semantic relational processing between the pair o f words (e.g., G raf & Schacter, 1985; but see Micco & Masson, 1991). Sensitivity o f an indirect memory test to a levels o f processing manipulation has been interpreted as evidence that a test is mediated, at least in part, by conscious recollective processes at retrieval (but see. Nelson, M cKinney, & Bennett, 1999, and Chapters 5 and 9).

Second, there is no evidence for reliable associative word stem completion prim ing or associative priming o f nonwords in moderate to densely amnesic patients (e.g.. Bowers & Schacter, 1993; Musen & Squire, 1993; Schacter & Graf, 1986b; Shimamura & Squire, 1989), whereas mild amnesics, with a degree o f spared conscious recollection, are capable o f successful associative word stem completion priming (Mutter et al., 1990; Schacter & Graf, 1986b). Nonetheless, amnesic patients appear to demonstrate intact associative word identification (Gabrieli, Keane, Zarella, & Poldrack, 1997a) and associative speeded naming o f degraded stimuli (M oscovitch et al., 1986, Expts. 2 & 3). One approach to disentangling these apparently discrepant findings is to evaluate the amount o f residual conscious recollective ability in amnesic patients. Accordingly, Shimamura and Squire (1989) reported that the amount o f associative prim ing obtained in amnesic patients was correlated with residual conscious recollective ability. Consequently, this overall pattern o f findings suggests that conscious processes are invoked, at least occasionally, during associative priming. Nevertheless, this pattern o f data can also support the contention that the failure to produce associative priming in amnesic patients is a consequence o f deficiencies in their ability to either encode elaboratively (Bowers & Schacter, 1993), or form the novel representations that support the unconscious retrieval o f associative information (Musen & Squire, 1993). More generally, there is an inherent circularity in the logic involved in utilising amnesic performance as a benchmark for unconscious retrieval (Ratcliff & M cKoon, 1996).

Third, evidence o f associative priming being compromised by conscious retrieval comes from the post-experimental assessment o f awareness o f the relation between study and test. Bowers and Schacter (1990) reported that only those participants classed as ‘aw are’ produced reliable associative priming (see also, Gooding, Mayes, van Eijk, M eudell, & M acDonald, 1999; cf. Howard et al., 1991; McKone & Slee, 1997, Expt. 2; Rybash, 1994). This suggests that associative priming, at least under certain experimental conditions, can be more accurately attributed to conscious processes, although others have argued that these influences are m ore likely to reflect the automatic activation o f conscious processes (Rybash, 1994), which has been referred to as involuntary conscious memory (e.g., Richardson-Klavehn et al., 1996, see also. Chapters 2, 6, & 9).

Fourth, the encoding conditions that are necessary for memory for new associations to be reliably produced such as self-paced study conditions, the elaborative semantic encoding o f each word pair, more than a single study trial (under some conditions), and long stimulus onset asynchronies (SOA) between items, are all factors that foster the use o f conscious memory processes (Durgunoglu & Neely, 1987; Roediger & McDermott, 1993). Specifically, for the associative word stem completion task, the potential contamination by conscious processes is particularly acute when the encoding conditions are self-paced in both young and older adults (Howard et al., 1991) and remains significant, particularly in young adults, even when the study interval is relatively short (Howard et al., 1991, 15s, Experiment 3). A reduction in the SOA simply eliminates the associative priming, even when elaborative encoding is performed at study (e.g., M cKone & Slee, 1997; Smith et al., 1989). In addition, very short SOAs cannot be simply implemented when testing old adults, because o f the generalised slowing associated with ageing (Salthouse, 1996).

In a typical task dissociation paradigm, both conscious and unconscious processes can lead to an increased tendency to respond to test cues with studied words. Following the review o f the experimental conditions under which associative priming is reported, it would appear that the phenomenological status o f associative priming is, as yet, unresolved. Indeed, both word stem completion and lexical decision are susceptible to contamination by conscious processes under indirect memory test retrieval instructions (McKone & Slee, 1997). Nonetheless, in the absence o f data to the contrary, the speeded naming o f degraded stimuli may represent a retrieval task that is likely to approach a veridical measure o f the unconscious retrieval o f associative information, but this task may not be appropriate for use with older adults (see Chapter 9).

1. Explicit-Implicit M emory and Ageing: Experimental W ork

1.4.1.2.1 M emory for New Associations: The Process Dissociation Approach.

The process dissociation procedure has been applied to investigate m em ory for related pairs o f words (Jacoby, 1994; Jacoby, 1996), and in two instances, memory for unrelated pairs o f words (Reingold & Goshen-Gottstein, 1996a; Reingold & Goshen-Gottstein, 1996b). However, these studies have only examined performance in young adults. The present subsection introduces and evaluates the critical issues identified by the studies conducted by Reingold and Goshen-Gottstein. These studies formed the basis for portions o f the experimental work that investigated the nature o f age-related differences in the contributions o f conscious and unconscious memory to perceptual- associative word stem completion (Chapters 6 and 8). The application o f the process dissociation procedure enables two distinct forms o f memory for new associations to be specified, within a dual process conceptualisation o f memory: (1) an associative memory effect mediated by conscious processes; and (2) an associative memory effect mediated by unconscious processes. Consistent with the independence relational model adopted by the process dissociation procedure (Jacoby,

1991), each o f these forms o f mem ory is assumed to independently contribute to memory task performance.

Reingold and Goshen-Gottstein (1996b) evaluated the contributions o f conscious and unconscious processes to associative word stem completion. Semantically unrelated context-target pairs o f words were presented during study, and context words and stems were presented during test in one o f three combinations: context-target (intact), context-different (recombined), and context-new word (control). In Experiment 1, the semantic encoding paradigm used by Schacter and G raf (1986a) was applied, in that participants were instructed to form a sentence that m eaningfully related the word pairs. However, Reingold and Goshen-Gottstein changed the perceptual encoding task from a vowel comparison task to a task that involved simply reading out the word pairs following presentation, since it has been argued that this encoding task represents a purer m easure o f shallow encoding (Roediger et al., 1989b). Cued recall and word stem completion revealed the standard pattern o f findings associated with a levels o f processing manipulation.

Experiment 2 was a replication o f Experiment 1, with the addition o f instructions at test modified in accordance with the process dissociation procedure. The findings suggested that in the semantic encoding condition, memory for new associations were largely mediated by conscious rather than unconscious processes (see also, Rybash, Santoro, & Hoyer, 1998). However, this conclusion needs to be tempered by the fact that there was no significant difference between the intact and

recombined conditions for the estimates o f unconscious processes. In order to demonstrate the influence o f the encoding instructions on the contributions o f conscious and unconscious processes, Experiment 3 employed the perceptually oriented copy instructions utilised by Micco and Masson (1991). The parameter estimates revealed that perceptually based associative word stem completion was almost exclusively mediated by unconscious processes.

Reingold and Goshen-Gottstein (1996a, Experiment 2) applied the process dissociation procedure to the perceptual encoding paradigm that involved presenting a line drawing depicting the context word alongside a corresponding word pair. Both the strong and weak cue encoding conditions were mediated by conscious and unconscious processes. The extent to which associative retrieval was based on unconscious processes was modified by the variation in overlap between encoding and retrieval, since the reduction in the overlap in the weak cue condition led to an increased role for the unconscious retrieval o f associative information (5% [weak cue] versus 8% [strong cue]; this difference was statistically significant). This is consistent with the nature o f the encoding manipulation, since the line drawing is likely to enhance the perceptual distinctiveness o f the encoding episode, which in turn supports the conscious recollection o f associative information (Reingold & Goshen-Gottstein, 1996a). Evidently, conscious processes are also modified by the extent to which perceptual processing is invoked across study-test conditions.

1.4.1.3 Summary

Age-related differences only occur consistently when people are given a single, brief opportunity to study the new pairs, and consequently insufficient time to complete the semantic elaboration necessary for associative priming. W ith longer study times, or more than one opportunity to study each pair, age-related differences are still apparent on the direct memory tests, but less so on the indirect memory tests. A mediating factor in single-trial associative prim ing appears to the extent to which perceptual processing is emphasised at encoding and test (Reingold & Goshen-Gottstein, 1996a). Therefore, it may be possible to obtain age-invariant single-trial perceptual-associative priming in older adults using the strong cue condition o f the paradigm developed by Reingold and Goshen-Gottstein (1996a). Further, conscious processes are present following elaborative encoding, whereas under shallow encoding that emphasises perceptual distinctiveness, the associative repetition effect is attributable, in part, to a mix o f both conscious and unconscious retrieval processes (Reingold & Goshen-Gottstein, 1996a). Combining this knowledge with a judicious selection o f variables applied in accordance with the process dissociation logic will provide

1. Explicit-Implicit M emory and Ageing: Experimental W ork

information related to nature o f the processes that support retrieval o f perceptual-associative information. Accordingly, this strategy was applied in the experimental work that addressed perceptual-associative word stem completion. Specifically, two basic variables, divided attention and directed forgetting, were applied to the perceptual-associative word stem completion task.