Consecuencias de la Desintegración Familiar

A number of studies of non-word repetition effects using the LDT appeared to support an abstractionist view of repetition effects. However the status of repetition effects with such novel stimuli has been controversial and may depend upon the task which subjects are required to perform. Forbach, Stanners and Hochhaus (1974) using a LDT found no evidence of non­ word repetition effects. On the other hand, a number of studies have all demonstrated reliable effects of non-word repetition in the LDT (Bentin & Moscovitch, 1988; Kirsner & Smith, 1974; Monsell, 1985; Scarborough, et al., 1977). However, in each case, the effects of non-word repetition differed qualitatively from the repetition effects seen with words. As described further in Section 1.8, words and non-words respond differently to increases in the interval between prime and probe encounters. Differences in repetition effects between non-words and words suggests that the two effects result from at least partially different mechanisms.

The interpretation of results of experiments using the LDT was called into question by Feustel et al (1983), who argued that the difference between word and non-word repetition effects in the LDT could result from a confounding of the lexical status of the stimulus and the response required. When a non-word is repeated, any episodic memory of its prior occurrence would tend to inhibit the making of a non-word response because the stimulus would be familiar, and therefore more word-like. This inhibition would offset any facilitatory effect arising from repetition, and might result in the absence of a repetition priming effect. Feustel et al (1983) suggested that in a task in which non-words were not subject to this inhibitory effect, non-word repetition priming effects would be evident.

Feustel et al (1983) used a perceptual identification task, a task with no response confound, to show that although identification thresholds were higher for non-words than for words, the benefit resulting from repetition was equivalent for the two stimulus types. Feustel et al (1983) argued that the differences between the recognition thresholds for words and non-words reflected the availability of pre-existing unitised abstract representations of words which were not available for non-words. In contrast, the repetition effects for non-words, and part of the effect with words, reflected the influence of episodic memories which were available equally for both stimulus types.

Dorfman (1994) has challenged this episodic account of non-word repetition effects. She compared the magnitude of the priming effects seen with non-words having morphological or syllabic structure with non-words having no such structure. She found that only non-words having morphemic or syllabic structure gave rise to reliable priming effects. Dorfman (1994) argued that non-word priming effects are dependent upon the use of abstract pre-existing representations rather than on the formation of new episodic representations. These pre-existing representations are of sublexical components such as syllables and morphemes rather than of words.

On their first enounter with a non-word subjects in the study reported by Rajaram and Neely (1992) either tried to remember the non-word for later recall or had to pronounce it. There were reliable repetition effects for non-words in a subsequent LDT for both study tasks. Rajaram and Neely (1992) suggested that performance of the LDT was facilitated to the degree that subjects constructing temporary 'lexical' representations of the non-words in the two tasks.

Bowers (1993) argued that if similar priming effects were found with illegal non-words to those found with legal non-words, then this pattern of effects would support the view that priming effects were not mediated by pre-existing lexical or sub-lexical representations. This was because illegal non-words do not contain letter clusters typically found in English words and hence would not engage pre-existing sub-lexical representations.

Bowers (1993) compared performance on a perceptual identification task and a recognition task for legal and illegal non-words which had been previously studied in either a structural

encoding task or a pronounciation task. Reliable priming effects were found for both the legal and illegal non-words. Bowers (1993) argued that the reliable effect found for illegal non­ words indicated that priming effects in perceptual identification tasks were not dependent upon pre-existing lexical representations. Bowers (1993) concluded that his results supported what he described as an 'acquisition-based' account of priming effects; an account in which priming effects were mediated by memory representations acquired in a single learning episode. Bowers' interpretation of his results can be challenged. Performance on the perceptual

identification task with illegal non-words was not clearly dissociated from performance on the recognition memory task. The magnitude of the priming effect in the pronunciation study task

was twice that in the structural study task, a result which contrasts with the dissociation found by Bowers for legal non-words and which is typically found for real words. The difference in the pattern of performance for legal and illegal non-words in the perceptual identification and recognition memory tasks suggests that different mechanisms were underlying the effects for the two types of stimuli. As Bowers (1993) acknowledges, it is possible that the priming effects with words and legal non-words were mediated by pre-existing sub-lexical representations. The nature of the processes underlying non-word priming effects, and the relation between word and non-word priming, has also been investigated by Rueckl (1990; Rueckl & Olds,

1993). Rueckl (1990) found a reliable repetition priming effect for words and legal non-words in a perceptual identification task. In addition, Rueckl (1990) found that when words or non­ words were preceded by an orthographically similar item of the same lexical status, reliable priming effects were also obtained, but were smaller than were the effects resulting from repetition. On the other hand, repetition priming effects seen with words were differentiated from the repetition effects seen with non-words, and from the orthographic priming effects seen with both words and non-words, by virtue of their response to multiple presentations of the prime. In contrast to the effects seen with words, for non-words three presentations of the prime did not result in a larger priming effect than did a single presentation (see also Light, LaVoie, & Kennison, 1995).

Reuckl (1990) suggested that non-word repetition and orthographic similarity effects resulted from interactions between orthographic representations, whilst the benefits of multiple repetitions for words arose because of a strengthening of the link between orthographic and semantic representations. Such an orthographic-semantic ‘co-activation’ effect would not normally occur for non-words because of the absence of a corresponding semantic

representation. Nor would such an effect occur between orthographically similar words since strengthening the orthographic-semantic link for the prime word would not aid the subsequent recognition of the probe word. Studies on the effects of the repetition of non-words to which arbitrary meanings have been assigned have also been reported by Whittlesea and Cantwell (1987) and by Rueckl and Olds (1993). The results of these studies have also supported the view that repetition effects may be mediated by links between orthographic and semantic representations.

However, an incremental priming effect for words and the absence of such an effect for non­ words was not found by Whitlow and Cebollero ( 1989 see also Soloman & Postman, 1952). Whitlow and Cebollero found that it was non-words that gave rise to an incremental priming effect with additional study presentations. In contrast, there was either no effect, or a much reduced effect, as a result of the multiple repetition of real words. Whitlow and Cebollero (1989) argued that the differences between the two types of stimuli reflected the effect of the presence of a pre-existing unified representation for words which was not available for non­ words. They suggested that the constant priming effects for words across multiple presentations

reflected the activation of lexical nodes, whilst the incremental effects for non-words reflected a process of'codification* (Salasoo, Shiffrin, & Feustel, 1985) thought to be involved in building new, relatively permanent representations. The reasons for the contrast between the results reported by Whitlow and Cebollero (1989) and Rueckl (1990) are not clear, but the differences between the results obtained with words and non-words within each study suggest that these two types of item are processed in different ways. This is consistent with there being a level of representation involved in word but not non-word repetition effects. Such an effect may involve lexical or semantic processing.

Non-word repetition priming effects have also been investigated under conditions in which it has been claimed that the contribution of episodic processes is reduced. Generally, one of two approaches have been taken. In the first, subjects perform an indirect task under conditions of divided attention. Such conditions are generally held to prevent elaborative encoding and thus prevent subsequent episodic retrieval (e.g. Jacoby, et al., 1989). The second approach involves the investigation of non-word priming effects in memory-impaired patients.

Smith and Oscar-Berman (1990) compared repetition under conditions of full and divided attention. When the data were normalised to equate performance across the two attention conditions, the shift from full to divided attention reduced the magnitude of the repetition effect for both words and non-words. The repetition effect on reaction times was still reliable for the words but not for the non-words. A reliable non-word repetition effect in the divided attention condition was evident however in the accuracy data. Subjects were more likely to misclassify repeating non-words as real words than to misclassify non-words appearing for the first time. Smith and Oscar-Berman (1990) found that this tendency to misclassify repeating non-words was also evident in a group of amnesic patients who also showed a repetition effect on reaction times for words but not for non-words. Smith and Oscar-Berman (1990) suggested that the reduced, but still reliable, priming effects for words under conditions of divided attention supported the view that repetition effects were a product of (at least) two different factors, one being dependent upon conscious attention, and one which was evident even under 'resource limited' conditions. The absence of this latter effect for non-words suggests that it may be specific to stimuli having unitised pre-existing lexical representations.

Repetition priming effects for non-words have been extensively studied by Cermak and his colleagues, particularly in amnesic patients suffering from Korsakoff s syndrome (e.g. Cermak, et al., 1985; Cermak, Verfaille, Milberg, Lettourneau, & Blackford, 1991; Verfaille, Cermak, Letourneau, & Zuffante, 1991). Cermak et al (1985) found that control subjects showed priming effects in a perceptual identification task for both words and non-words. On the other hand amnesic patients showed reliable priming effects for real words, but there was no such priming effect for non-words.

In a subsequent re-analysis of these results, Cermak et al (1991) suggested that when the priming effects were analysed as a proportion of the baseline score, the priming effects for non­ words in the amnesic subjects were reliable, although smaller than the effects seen in the control subjects. They also suggested that, because these effects were dependent upon the structure of the word lists used in the experiment, priming effects with these stimuli do not occur automatically. Rather the availability of a unitised code for the non-word in respect of either its pronunciation or the meaning of the corresponding word must be salient before the priming effects are observed.

Cermak et al (1985) argued that the absence of priming effects for non-words in amnesic patients resulted from their inability to use episodic information to enhance their performance, and from the lack of pre-existing representations of the non-words which could mediate priming effects. For words, priming effects were observed because of the availability of a pre­ existing representation. For the control subjects both the creation of episodic representations, and changes in abstract pre-existing representations may facilitate performance for words. However, only the former process would be available to enhance identification of the non­ words. The non-word priming effects in amnesics demonstrated by Cermak et al (1991) may be accounted for either in terms of the priming of sub-lexical constituents as suggested by

Dorfman (1994), or as reflecting preserved explicit memory in the amnesic patients.

Musen and Squire (1991) have also demonstrated reliable priming effects for words and non­ words. In their study amnesic patients were required to read lists of words and non-words as quickly as possible; a task which Musen and Squire (1991) argued would only minimally invoke episodic memory. Priming effects persisted even when 10 minutes intervened between the two presentations of the stimuli lists. Musen and Squire (1991) argued that the priming effects they observed were unlikely to be due to processes concerned with episodic memory, but because the effects for the putatively novel non-word stimuli were as large, or larger, than were the effects with words, they also argued that the effects were not mediated by pre-existing representations. Rather, Musen and Squire (1991) argued that the priming effects were a reflection of changes in a perceptual representation system concerned with word recognition. This interpretation is however dependent upon accepting that orthographically legal non-words are genuinely novel stimuli, a claim that, as described above, has been questioned.

To summarise the results of studies which have used non-words as stimuli: The absence of priming effects for non-words in the LDT cannot be taken as evidence of the importance of pre­ existing lexical representations in repetition effects. This is because of the response confound involved in this task. Although demonstrations of reliable non-word priming effects indicate that repetition effects may depend upon episodic memory for particular prior occurrences, such demonstrations cannot be taken as strong evidence for the involvement of such episodic processes in repetition effects. This is because orthographically legal non-words cannot be seen as genuinely novel stimuli. Repetition effects with these stimuli may reflect processes that

involve pre-existing sub-lexical representations. Dissociative effects seen with words and non­ words may reflect lexical processes engaged by words but not non-words. The addition of conceptual information enhances repetition effects with stimuli which have no prior unitised representations such as non-words. However, this does not necessarily mean that conceptual processes play a role in repetition effects with stimuli which do have such pre-existing unitised representations, e.g words.