The Word Completion Memory Test (WCMT): a new test to detect malingered memory deficits.

In recent years, much research has focused on developing tests to detect malingering. A drawback of existing tests is their poor ability to detect malingerers possessing more "sophisticated" knowledge of neuropsychological deficits. The current study presents preliminary validation data on a new measure, the Word Completion Memory Test (WCMT), which is the first malingering test to utilize a sophisticated coaching methodology in its development. The WCMT was administered to control participants, memory-impaired patients, and coached simulators. The coached simulators were provided with specific information about and examples of memory deficits commonly experienced following closed head injury (CHI; e.g., anterograde vs. retrograde amnesia). They also read a detailed scenario describing the lifestyle and motivations likely experienced by CHI litigants, and then practiced their roles by taking a quiz about their deficits. Results showed that 93% of coached simulators and 100% of control and memory-impaired participants were correctly classified by the WCMT.

Manipulations of irrelevant information: suffix effects with articulatory suppression and irrelevant speech.

Numerous studies have demonstrated impaired recall when the to-be-remembered information is accompanied or followed by irrelevant information. However, no current theory of immediate memory explains all three common methods of manipulating irrelevant information: requiring concurrent articulation, presenting irrelevant speech, and adding a stimulus suffix. Five experiments combined these manipulations to determine how they interact and which theoretical framework most accurately and completely accounts for the data. In Experiments 1 and 2, a list of auditory items was followed by an irrelevant speech sound (the suffix) while subjects engaged in articulatory suppression. Although articulatory suppression reduced overall recall compared to a control condition, comparable suffix effects were seen in both conditions. Experiments 3 and 4 found reliable suffix effects when list presentation was accompanied by irrelevant speech. Experiment 5 found a suffix effect even when the irrelevant speech was composed of a set of different items. Implications for working memory, precategorical acoustic store, the changing-state hypothesis, and the feature model are discussed.

Role of study strategy in recall of mixed lists of common and rare words.

Experiment 1 confirmed previous findings that common words are more recallable than are rare words when the 2 kinds of words are presented in separate lists but not when they are presented in the same list. Experiment 2 showed much the same pattern when an orienting task was performed during word presentation. In Experiment 3 common words were found to be more recallable than rare words even for mixed lists when no warning was given of the memory test, although the effect was less pronounced than for pure lists. In Experiment 4 stronger measures were taken to preclude anticipation of the memory test, and the effect of word commonness was found to be just as pronounced with mixed lists as it was with pure lists. It was suggested that lists are studied in a way believed to optimize recall and that mixed lists foster a strategy of favoring the rare words.

Age and individual differences influence prospective memory.

The influence of age and individual ability differences on event-based prospective memory was examined using an adapted version of G. O. Einstein and M. A. McDaniel's (1990) task. Two samples of younger and older adults who differed in educational attainment, occupational status, and verbal ability were compared. Results yield comparable prospective performance for the younger groups and higher ability older adults; lower ability older adults performed more poorly by comparison. Hierarchical regression analyses indicated that working memory span and recognition accounted for small but significant proportions of variance in prospective performance. The contribution of ability level to prospective memory remained significant even after statistically controlling for self-reported health and social activity characteristics. Implications for current views on prospective memory aging are discussed.

The importance of semantic similarity to the irrelevant speech effect.

Irrelevant speech disrupts immediate recall of a short sequence of items. Salamé and Baddeley (1982) found a very small and nonsignificant increase in the irrelevant speech effect when the speech comprised items semantically identical to the to-be-remembered items, leading subsequent researchers to conclude that semantic similarity plays no role in the irrelevant speech effect. Experiment 1 showed that strong free associates of the to-be-remembered items disrupted serial recall to a greater extent than words that were dissimilar to the to-be-remembered items. Experiment 2 showed that this same pattern of disruption in a free recall task. Theoretical implications of these findings are discussed.

Irrelevant speech eliminates the word length effect.

The word length effect refers to the observation that memory is better for short than for long words. The irrelevant speech effect refers to the finding that memory is better when items are presented against a quiet background than against one with irrelevant speech. According to Baddeley's (1986, 1994) working memory, these variables should not interact: The word length effect arises from rehearsal by the articulatory control process, whereas irrelevant speech reduces recall through interference in the phonological store. Four experiments demonstrate that, like articulatory suppression, irrelevant speech eliminates the word length effect for both visual and auditory items. These results (1) provide further evidence against the ability of working memory to explain the word length and irrelevant speech effects and (2) confirm a specific prediction of Nairne's (1990) feature model.

Irrelevant speech and irrelevant tones: the relative importance of speech to the irrelevant speech effect.

Irrelevant auditory stimuli disrupt immediate serial recall. In the equipotentiality hypothesis, D. M. Jones and W. J. Macken (1993) made the controversial prediction that speech and tones have an equivalent disruptive effect. In the present study, 5 experiments tested their hypothesis. Experiments 1-4 showed that meaningful speech disrupts recall more than do tones. Experiments 3 and 4 provided some evidence that meaningful speech disrupts recall more than does meaningless speech, and Experiment 4 showed that even meaningless speech disrupts recall more than do tones. Using slightly different experimental procedures, Experiment 5 showed that letters disrupt recall more than do tones. Implications of these results for a number of theories of primary memory and the irrelevant speech effect are discussed.

On the irrelevance of phonological similarity to the irrelevant speech effect.

Irrelevant background speech disrupts immediate recall of visually presented items. Salamé and Baddeley (1982) found that increasing the phonological similarity between the irrelevant speech and the visual items greatly increased this disruption. In contrast, Jones and Macken (1995) found little evidence for such an increase. The present experiments directly manipulated the phonological similarity of the irrelevant speech background and the to-be-remembered visual items. Experiments 1-4 compared background speech that shared virtually no phonemes with the visual stimuli with background speech that shared all of the phonemes of the visual stimuli. No effect of phonological similarity was found. Experiment 5 replicated the method of Salamé and Baddeley's critical experiment but not their results. With regard to the two primary explanations of the irrelevant speech effect, these data present a strong challenge to the phonological store hypothesis while offering some support to the changing state hypothesis.

Irrelevant speech, serial rehearsal, and temporal distinctiveness: a new approach to the irrelevant speech effect.

D. C. LeCompte (1994) showed that the irrelevant speech effect--that is, the impairment of performance by the presentation of irrelevant background speech--extends to free recall, recognition, and cued recall. The present experiments extended the irrelevant speech effect to the missing-item task (Experiments 1 and 2), thereby contradicting a key prediction of the changing state hypothesis, which states that tasks that do not involve serial rehearsal should not be affected by the presence of irrelevant speech. Temporal distinctiveness theory provides an alternative explanation of the irrelevant speech effect. Experiment 3 tested and confirmed a unique prediction of this theory.

Visual distinctiveness can enhance recency effects.

Experimental efforts to meliorate the modality effect have included attempts to make the visual stimulus more distinctive. McDowd and Madigan (1991) failed to find an enhanced recency effect in serial recall when the last item was made more distinct in terms of its color. In an attempt to extend this finding, three experiments were conducted in which visual distinctiveness was manipulated in a different manner, by combining the dimensions of physical size and coloration (i.e., whether the stimuli were solid or outlined in relief). Contrary to previous findings, recency was enhanced when the size and coloration of the last item differed from the other items in the list, regardless of whether the "distinctive" item was larger or smaller than the remaining items. The findings are considered in light of other research that has failed to obtain a similar enhanced recency effect, and their implications for current theories of the modality effect are discussed.

Recollective experience in the revelation effect: separating the contributions of recollection and familiarity.

The revelation effect is a phenomenon of recognition memory in which words presented for a recognition decision are more likely to be identified as previously studied if they are initially disguised and are then somehow revealed to the subject. The goal of the present experiments was to determine whether the revelation effect has similar or different influences on the conscious recollection of a previous encounter with a test item and on the feeling of familiarity evoked by a test item. The process-dissociation procedure (Experiment 1) and the remember/know procedure (Experiment 2) were used to achieve this goal. The main findings of these experiments were that revealing an item at test (1) increased the feeling of familiarity associated with that item, especially if it was not previously studied, and (2) decreased conscious recollection of previously studied items. These data narrow the range of potential explanations of the revelation effect.

Grouping in primary memory: the case of the compound suffix.

Appending a nominally irrelevant item, or "suffix," to the end of a short list of items impairs recall of the list. Appending a second such item, however, does not increase the impairment. The research reported here shows that the impairment can in fact be increased if the suffix items are physically dissimilar. Thus, Experiments 1-4 show that memory for a sequence of digits is impaired more by the addition of two zeros uttered in different voices than by either a single zero or two zeros uttered in the same voice. Experiment 5 shows a similar pattern of results in the visual modality, with physical similarity defined by typefont. The findings are contrary to at least two theories of the suffix effect but can be accounted for by assuming that physically similar items tend to form a cohesive group.

A comparison of item and source forgetting.

The purpose of the present research was to compare memory for an item with memory for the item's source. Experiment 1 investigated discrimination between two external sources: each item in a list of words was spoken in either a male or a female voice. Subjects received a test of item recognition and a test of source monitoring at each of four delay intervals (immediate, 30 min, 48 h, 1 week). In contrast with previous research, no evidence of differential forgetting rates for item and source information was found. With delay intervals of 0 and 48 h, Experiment 2 replicated Experiment 1 while adding a reality monitoring condition that required discrimination between an internal (i.e., self-generated) and an external source. Subjects were better at making internal-external discriminations than at making external-external discriminations, but both types of source monitoring declined at the same rate as memory for the items themselves.

An irrelevant speech effect with repeated and continuous background speech.

The irrelevant speech effect is the impairment of task performance by the presentation of to-be-ignored speech stimuli. Typically, the irrelevant speech comprises a variety of sounds, but previous research (e.g., Jones, Madden, & Miles, 1992) has suggested that the deleterious effect of background speech is virtually eliminated if the speech comprises repetitions of a sound (e.g., "be, be, be") or a single continuous sound (e.g., "beeeeeee"). Four experiments are reported that challenge this finding. Experiments 1, 2, and 4 show a substantial impairment in serial recall performance in the presence of a repeated sound, and Experiments 3 and 4 show a similar impairment of serial recall in the presence of a continuous sound. The relevance of these findings to several explanations of the irrelevant speech effect is discussed.

Extending the irrelevant speech effect beyond serial recall.

The irrelevant speech effect is the impairment of immediate memory by the presentation of to-be-ignored speech stimuli. The irrelevant speech effect has been limited to serial recall, but this series of 8 experiments demonstrates that it is considerably more general. Experiments 1-3 show that (a) irrelevant speech inhibits free recall more than does white noise, (b) irrelevant speech impairs free recall even when the speech occurs after the to-be-recalled items, and (c) free recall is inhibited even when the speech is meaningless. Experiment 4 failed to find an effect in free recall with 16-item lists. Experiments 5A-5C extend the effect to recognition of 8-, 12-, and 16-item lists, with both phonologically related and phonologically unrelated lure items. Experiment 6 extends the effect to a cued recall task that discourages the use of serial rehearsal of the to-be-remembered items.

Similarity as an organising principle in short-term memory.

The role of stimulus similarity as an organising principle in short-term memory was explored in a series of seven experiments. Each experiment involved the presentation of a short sequence of items that were drawn from two distinct physical classes and arranged such that item class changed after every second item. Following presentation, one item was re-presented as a probe for the 'target' item that had directly followed it in the sequence. Memory for the sequence was considered organised by class if probability of recall was higher when the probe and target were from the same class than when they were from different classes. Such organisation was found when one class was auditory and the other was visual (spoken vs. written words, and sounds vs. pictures). It was also found when both classes were auditory (words spoken in a male voice vs. words spoken in a female voice) and when both classes were visual (digits shown in one location vs. digits shown in another). It is concluded that short-term memory can be organised on the basis of sensory modality and on the basis of certain features within both the auditory and visual modalities.

Short-term memory for the timing of auditory and visual signals.

Short-term memory for the timing of irregular sequences of signals has been said to be more accurate when the signals are auditory than when they are visual. No support for this contention was obtained when the signals were beeps versus flashes (Experiments 1 and 3) nor when they were sets of spoken versus typewritten digits (Experiments 4 and 5). On the other hand, support was obtained both for beeps versus flashes (Experiments 2 and 5) and for repetitions of a single spoken digit versus repetitions of a single typewritten digit (Experiment 6) when the subjects silently mouthed a nominally irrelevant item during sequence presentation. Also, the timing of sequences of auditory signals, whether verbal (Experiment 7) or nonverbal (Experiments 8 and 9), was more accurately remembered when the signals within each sequence were identical. The findings are considered from a functional perspective.

In search of a strong visual recency effect.

When a sequence of visual stimuli is presented in a fixed location, immediate serial recall of the sequence is characterized by only a small recency effect. According to Battacchi, Pelamatti, and Umiltà (1990), the distribution of visual stimuli over space, as well as time, greatly enhances the recency effect. After an initial failure to find a strong visual recency effect with distributed presentation (Experiment 1), in the remaining experiments an attempt was made to more closely approximate Battacchi et al.'s methodology by eliminating articulatory suppression (Experiments 2-7), using their stimuli (Experiments 3-7), blocking conditions (Experiments 4-7), requiring written rather than typed responses (Experiments 5-7), and using their list length (Experiments 6 and 7). Nevertheless, even when their method was followed as closely as possible (Experiment 7), distributed presentation did not produce a strong visual recency effect. The influence of distributed presentation on the visual recency effect would seem to be, at best, limited.

Inadequacy of recall as a basis for frequency knowledge.

Subjects studied a word list comprising varying numbers of words from distinct semantic categories. The category names (trees, colors, etc.) were then re-presented, and for each name subjects either recalled as many exemplars as they could or estimated how many had been included in the list (Experiments 1 and 2). Recall was not sufficiently informative about actual category sizes to account for performance in the frequency estimation task. Moreover, it remained insufficiently informative when efforts were made to induce a recall-estimate strategy by requiring overt recall prior to estimation (Experiments 3-5), by using very small categories (Experiment 4), and by not showing the category name at study (Experiment 5), even though it did allow a partial account of estimation when the category exemplars were individually cued (Experiment 6). It is concluded that the role of recall in frequency estimation is much exaggerated.