Memory in educable mentally retarded adults: Deficit in subject or experimenter?

Educable mentally retarded (EMR) and nonretarded adults free recalled lists of (a) words, (b) minitasks performed by the subjects (SPTs), (c) minitasks performed by the experimenter (EPTs), or (d) task instructions. The EMR subjects were significantly inferior to the nonretarded subjects in the immediate recall of words, EPTs and instructions, but not in the immediate recall of SPTs. This proficiency of the EMR subjects in SPT recall was attributed to the nonstrategic nature of this test. The EMR subjects were, however, inferior to the nonretarded subjects in a final free recall (recall of all lists) of all four types of item.     

The item-order hypothesis reconsidered: The role of order information in free recall

According to the item-order approach of free recall, in pure short lists the free recall of unrelated items is organized according to their order of presentation in the study list. The approach was applied in the present study to experimenter-performed tasks (EPTs) and subject-performed tasks (SPTs). It claims that EPTs provide better serial order information than SPTs. Consequently, free recall of EPTs should be more organized along the presentation order of the items than the free recall of SPTs. In three experiments, some specific aspects of this approach were studied. Firstly, it was demonstrated that serial retrieval is not strongly used spontaneously and that its use is overestimated in the literature because it is usually evoked by an order reconstruction test which follows free recall testing. Secondly, a serial retrieval strategy in free recall can be encouraged by explicit instructions. Finally, the present experiments showed that a serial output strategy alone does not allow one to predict performance in free recall. The implications of these findings for the item-order approach will be discussed.     

The word-length effect in probed and serial recall

The word-length effect in immediate serial recall has been explained as the possible consequence of rehearsal processes or of output processes. In the first experiment adult subjects heard lists of five long or short words while engaging in articulatory suppression during presentation. Full serial recall or probed recall for a single item followed the list either immediately or after a 5-second delay to encourage rehearsal. The word-length effect was not influenced by recall delay, but was much smaller in probed than in serial recall. Examination of the serial position curves suggested that this might be due to a recency component operating in probed recall. Experiment 2 confirmed a word-length-insensitive recency effect in probed recall and showed that this was resistant to an auditory suffix, unlike the small recency effect found in serial recall. Experiment 3 used visual presentation without concurrent articulation. Under these conditions there was no recency effect for either recall method, but the word-length effect was again much smaller in probed than in serial recall. This was confirmed in Experiment 4, in which the presentation of serial and probed recall was randomized across trials, showing that the differences between recall methods could not be due to encoding strategies. We conclude that for visual presentation, at least part of the word-length effect originates in output processes. For auditory presentation the position is less clear, as serial and probed recall appear to draw on different resources. The nature of the output processes that may give rise to word-length effects is discussed.     

Is there a modality effect? Evidence for visual recency and suffix effects

In Experiment 1, four groups of 16 subjects performed ordered recall of six-syllable lists in both suffix and nonsuffix conditions. Sequential presentation of the lists varied for each group. In the auditory presentation, the syllables were delivered from one location only and were read aloud by the subjects. For the visual, spatially nondistributed presentation, the syllables appeared in one location only and were read silently. For visual, spatially distributed presentations, the syllables were spread out either vertically or horizontally and were read silently. Very robust recency and suffix effects were found in the auditory presentation, as well as in visual, spatially distributed presentations. In Experiment 2, 16 subjects performed ordered recall of visually presented lists with the items spread out vertically and conflicting spatial and temporal orders. A reliable recency effect was found for the final block of trials. In Experiment 3, 16 subjects performed ordered recall in the same conditions as in Experiment 2, except that they were instructed to recall the temporal order in which the spatial positions would be filled in. A bow-shaped curve and a strong recency effect were obtained.     

A recency-based account of the primacy effect in free recall

Seven experiments investigated the role of rehearsal in free recall to determine whether accounts of recency effects based on the ratio rule could be extended to provide an account of primacy effects based on the number, distribution, and recency of the rehearsals of the study items. Primacy items were rehearsed more often and further toward the end of the list than middle items, particularly with a slow presentation rate (Experiment 1) and with high-frequency words (Experiment 2). Recency, but not primacy, was reduced by a filled delay (Experiment 3), although significant recency survived a filled retention interval when a fixed-rehearsal strategy was used (Experiment 4). Experimenter-presented schedules of rehearsals resulted in similar serial position curves to those observed with participant-generated rehearsals (Experiment 5) and were used to confirm the main findings in Experiments 6 and 7.     

Recall of semantic clusters in primary memory

An experiment is reported which investigated the use of semantic relatedness as a retrieval cue in the primary memory component in a free recall task. Six-word semantically related clusters were placed in the middle and end positions of free recall lists. Retention was measured immediately after the list presentation and after a filled retention interval of 15 sec. Pure primary memory functions were calculated. The results indicated that semantic cues are useful in retrieval from secondary memory but played no part in recall from primary memory.     

On the generality of some memory laws

Several memory laws have been established for the free recall of word lists. The generality of some of these laws were tested, using tasks which the subjects performed (SPTs) as to-be-recalled list items. SPT recall obeyed one law of word recall in showing a strong positive recency effect in immediate free recall, which appeared to be due to these events being in a temporary state of high accessibility. Differences between word and SPT recall were: 1) The reliable primacy effect associated with word recall did not appear in SPT recall; 2) Subjects reported using active memorisation strategies for word lists, but not for SPT lists; 3) Unlike word recall, diverting the subject's attention to so-called deep or shallow features of the SPTs during presentation did not affect the level of their recall. These results considered together with Cohen & Stewart's (1981) finding that SPT recall was not age-sensitive were taken to indicate that SPTs should be regarded as a different class of memory event than words, and that memory models dealing with SPT recall should de-emphasize the importance of encoding, stressing instead retention, and retrieval operations.     

Pop-out into memory: a retrieval mechanism that is enhanced with the recall of subject-performed tasks

Subject-performed tasks (SPTs; i.e., carrying out the actions during study) improve free recall of action phrases without enhancing relational information. By this mechanism, items pop into a person's mind without active search, and this process especially extends the recency effect. The authors demonstrated the existence of the extended recency effect and its importance for the SPT recall advantage (Experiments 1 and 2). Carrying out the action and not semantic processing caused the effect (Experiment 3). The extended recency effect was also not a consequence of a deliberate last-in, first-out strategy (Experiment 4), and performing a difficult secondary task (an arithmetic task) during recall reduced memory performances but did not influence the extended recency effect (Experiment 5). These data support the theory that performing actions during study enhances the efficiency of an automatic pop-out mechanism in free recall.     

Categorical-relational and order-relational information in memory for subject-performed and experimenter-performed actions

Memory for self-performed tasks (SPTs) is better than memory for experimenter-performed tasks (EPTs). In short unrelated lists of actions this effect occurs if the encoding condition is manipulated within subjects. In a between-subjects design, the enactment effect disappears (J. Engelkamp & D. Dehn, 2000; J. Engelkamp & H. D. Zimmer, 1997). These findings were explained by the item-order hypothesis, which claims that encoding order information depends on the type of encoding and design. The authors demonstrate that this differential encoding of order information in EPTs and SPTs is not effective in free recall if categorized lists are used. The use of categorized lists makes the interaction of type of encoding and design in free recall of short lists disappear, and the enactment effect reappears independent of the type of design.     

Simple drawing and pattern completion techniques for studying visualization and long-term visual knowledge

Simple and efficient drawing and completion tasks for studying visual memory are developed. In Experiment I subjects reproduced a series of matrix patterns by filling empty matrices. The serial position function was fiat, except that accuracy was much higher for final patterns. In Experiment 2 this recency effect was removed by an interpolated pattern classification task. Experiments 3 and 4 examined the effect of counting backward during intervals of from 3 to 15 sec on the recall of single patterns. Drawings were much less accurate after filled intervals but the duration of the interval had no effect. Experiment 5 tested retention of series of patterns using a completion task. On immediate test the serial position function was the same as in Experiments 1 and 2. On a final test accuracy was unchanged except for final items, which then showed a small negative recency effect. It is argued that performance is so similar in the drawing, completion, and previously reported recognition tasks because in all it is based upon the use of general-purpose knowledge accessible to voluntary processing. Visualization in these tasks is analogous to but different from verbal STM. One main difference is that there is no sign of temporary storage of visualized information after attention has turned to other things.     

Developmental differences in episodic memory across school ages: evidence from enacted events performed by self and others

The aim of this study was to examine action memory as a form of episodic memory among school-aged subjects. Most research on action memory has focused on memory changes in adult populations. This study explored the action memory of children over time. A total of 410 school-aged child participants, comprising 201 girls and 208 boys in four age groups (8, 10, 12, and 14), were included in this study. We studied two forms of action encoding, subject-performed tasks (SPTs) and experimenter-performed tasks (EPTs), which were compared with one verbal encoding task as a control condition. At retrieval, we used three memory tests (free recall, cued recall, and recognition). We observed significant differences in memory performance in children aged 8–14 years with respect to free recall and cued recall but not recognition. The largest memory enhancement was observed for the SPTs in the 8–14-year-old participants under all test conditions. Participants performed equally well on the free recall of SPTs and EPTs, whereas they displayed better performances on the cued recall and recognition of SPTs compared to EPTs. The strategic nature of SPTs and the distinction between item-specific information and relational information are discussed.     

Examining the relationship between free recall and immediate serial recall: the effect of concurrent task performance

In 3 experiments, participants saw lists of 16 words for free recall with or without a 6-digit immediate serial recall (ISR) task after each word. Free recall was performed under standard visual silent and spoken-aloud conditions (Experiment 1), overt rehearsal conditions (Experiment 2), and fixed rehearsal conditions (Experiment 3). The authors found that in each experiment, there was no effect of ISR on the magnitude of the recency effect, but interleaved ISR disrupted free recall of those words that would otherwise be rehearsed. The authors conclude that ISR and recency cannot both be outputs from a unitary limited-capacity short-term memory store and discuss the possibility that the process of rehearsal may be common to both tasks.     

Serial position curves in spatial memory of rats: Primacy and recency effects

Memory for lists of items was tested in rats (N = 18) in an 8-arm radial maze. In Experiment 1 trials consisted of a study phase, in which the rat could freely choose five arms to obtain a food reward, and a test phase in which the animal was presented with a choice between a novel and a previously visited arm. The rat received additional food reinforcement only when visiting the novel arm. The two phases of a trial were separated by a retention interval of 30 sec or of 4, 16 or 60 min. It was found that recall of the five free arm choices was related to the serial position of the previously visited arm. There was a significant recency effect at the 30-sec delay. With longer retention intervals this disappeared, and a significant primacy effect could be observed. In Experiment 2 the same animals were given forced arm entries during the study phase and delays of 30 sec or 4 or 16 min before the test phase. Again, there was a trend towards a recency effect after the shorter delays and a significant primacy effect after the 16-min interval. These results show that, in the recall of lists of spatial items, rats have serial position curves with primacy and recency effects, depending on the length of the retention interval.     

Recall accuracy and illusory memories: when more is less

In two experiments it was revealed that manipulations that increased recall of studied list items also increased false recall of theme-related, critical nonpresented words. In Experiment 1 subjects listened to a series of short word lists, each containing items associatively related to a theme, while engaging in either semantic or nonsemantic processing. On an immediate free recall test semantic processors demonstrated greater correct recall as well as more illusory memories of critical nonpresented items than nonsemantic processors. In Experiment 2, the short study lists were combined to form longer lists that were presented either blocked by theme or in a random presentation order. Retention interval was also varied as participants were tested either immediately, one week after, or three weeks after the study phase. Presenting the target items in a blocked, as opposed to random, format increased recall accuracy, but this was at the expense of a higher intrusion rate for theme-consistent items. Interestingly, the level of false memories was not affected by retention interval even though typical decrements in the recall of study items were observed over time. The results of these experiments highlight the persistence of the false memory effect, as well as pointing to several factors, primarily semantic processing, that may lead to the creation of false memories. Interpretations are offered within the theoretical frameworks of source monitoring and fuzzy trace theory.     

Multiple mechanisms for recency with vowels and consonants

Three experiments were conducted to test the hypothesis that the difference in recency effect between vowel-contrasting and stop-contrasting lists of syllables in immediate ordered recall can be explained by item discriminability and regular short-term memory mechanisms, without any recourse to echoic memory or precategorical acoustic storage (PAS). In Experiment 1, the short-term memory mechanisms were manipulated by reducing amount of output interference and length of retention interval. The partial-report technique was used. The most important finding was the usual final-position recency effect (difference in recall between the fifth and sixth serial positions) for the vowel lists but not for the stop lists, regardless of the type of report. Thus the PAS theory could not be rejected. In Experiments 2 and 3, the last item was differentiated from the other items of the list, either by lengthening the interstimulus interval between the last and the next-to-last (Experiment 2) or by increasing the intensity of the last item (Experiment 3). In both cases, an increase of the final-position recency effect was found even for stop lists. Since a drop in recall errors was also obtained for the fourth item when its intensity was increased (von Restorff effect), this final-position recency effect for stop lists is likely to be due to item discriminability, and not to echoic memory for the last item. Item discriminability appeared to be the critical factor.     

Recency effect in recall of a word list when an immediate memory task is performed after each word presentation

Subjects studied 12-word lists for free recall. During presentation of the lists, each word was followed by a supraspan sequence of digits, which the subjects tried to reproduce. This task, unlike those used in previous research with this continual distractor procedure, presumably taxed immediate memory capacity to the full. Nevertheless, the word recall data showed a pronounced recency effect. Moreover, the magnitude of the recency effect was found to be just as great with this task as with a more typical task in which the demands on immediate memory are likely to be fewer. These findings reinforce the emerging view that the recency effect need not be the product of immediate memory.     

Time of day and processing strategy in free recall

Consistent effects of time of day have been observed in digit span/sequence performance, and in the immediate memory for information presented in prose. However, studies using syntactically unstructured word lists have yielded inconsistent results. Three experiments were conducted that examined the free recall of 15 word lists. In all three, immediate recall from the pre-recency positions was found to be superior in the morning to the afternoon. This superiority disappeared after a 20-min delay (Experiment 1) and under articulatory suppression (Experiment III), but was unaffected by a manipulation that equated recall order (Experiment II). Immediate recall from the recency positions showed a W-shaped trend over the day (Experiment I) that might account for the inconsistencies previously reported. It is suggested that the changes in recall from the pre-recency positions may reflect a decrease in maintenance, and increase in elaboration, over the day. Such a change in processing strategy could itself reflect an increase in attentional selectivity associated with the changes in basal arousal level commonly held to occur over the day.     

Predictability as a task demand in single-trial free recall

In a series of five single-trial free recall experiments it was demonstrated how manipulations of predictability in a list learning task caused reliable effects on the recency portions of the nominal serial position curve. Predictability was defined as knowledge of when the next item in the list should appear ( interval predictability) and knowledge of when the list should end and thus when recall could start ( signal predictability). Predictability was manipulated by varying the inter-item intervals within a list according to different "encoding functions", e.g. a successive increase (Condition I ) or decrease (Condition D ) of the inter-item intervals. Predictability was also manipulated by means of post-list recall signals. The data obtained show, that depending on how the interval and the signal predictabilities were manipulated, either Condition I or Condition D lists could be made more beneficial to the recall of recency items than lists with constant inter-item intervals (Condition C ). Previous encoding, storage and retrieval models were found not to give satisfactory accounts of the obtained recency effects. Neither could any traditional rehearsal model explain the data. Instead it is proposed that the predictability of stimuli in a list learning task explains how changes in recall of recency items come about. It was also hypothesized that the temporal demands, afforded to the subjects by the different encoding functions, explained the obtained output order variations.