Word-length effects in immediate memory: Overwriting trace decay theory

Memory is worse for items that take longer to pronounce, even when the items are equated for frequency, number of syllables, and number of phonemes. Current explanations of the word-length effect rely on a time-based decay process within the articulatory loop structure in working memory. Using an extension of Nairne’s (1990) feature model, we demonstrate that the approximately linear relationship between span and pronunciation rate can be observed in a model that does not use the concept of decay. Moreover, the feature model also correctly predicts the effects of modality, phonological similarity, articulatory suppression, and serial position on memory for items of different lengths. We argue that word-length effects do not offer sufficient justification for including time-based decay components in theories of memory.     

Input restriction and immediate memory decay in normal and subnormal children

Twelve imbeciles and 12 normals, matched for their digit memory span, were presented with three digit numbers successively and simultaneously. Seven speeds of presentation were used. Each simultaneous speed of presentation had a corresponding successive speed. Subjects were required to recall digits on the conclusion of presentation of each number. Each performance was scored as the number of errors for each digit. With simultaneous presentations the difference between the groups was significant only at fast presentation speed, where the normals were significantly better than the imbeciles. Imbeciles improved at slow speeds and became as good as normals. In the case of successive presentations differences between groups occur only in relation to the second digit, which the normals remember better than the subnormals. Both groups remember the first digit worst as rates of presentation become progressively slower. Results are explained in terms of input restriction and of memory trace decay.     

Collaboration can improve individual recognition memory: Evidence from immediate and delayed tests

In two experiments, we tested the effects of collaboration on individual recognition memory. In Experiment 1, participants studied pictures and words either for meaning or for surface properties and made recognition memory judgments individually either following group discussion among 3 members (collaborative condition) or in the absence of discussion (noncollaborative condition). Levels of processing and picture superiority effects were replicated, and collaboration significantly increased individual recognition memory. Experiment 2 replicated this positive effect and showed that even though memory sensitivity declined at longer delays (48 h and 1 week), collaboration continued to exert a positive influence. These findings show that (1) consensus is not necessary for producing benefits of collaboration on individual recognition, (2) collaborative facilitation on individual memory is robust, and (3) collaboration enhances individual memory further if conditions predispose individual accuracy in the absence of collaboration. Psychonomic Society, Inc. nt]pra|Parts of the research reported in this article were presented at the 77th Annual Meeting of the Eastern Psychological Association, Baltimore.     

Using immediate memory span

To avoid some conceptual and methodological pitfalls found in traditional artificial grammar learning tasks, we developed a new method of measuring implicit learning using immediate memory span. Subjects were presented with sequences generated by an artificial grammar and were asked to reproduce the patterns by pressing buttons on a response box. After exposure to these sequences, subjects showed selective improvement in immediate memory span for novel sequences governed by the same grammar. Individual differences in implicit learning covaried with measures of auditory digit span. Subjects with greater immediate memory processing capacity were better able to learn and subsequently exploit the information available in grammatical sequences. Our results are consistent with a detailed episodic coding framework in which implicit learning occurs as an incidental by-product of explicit task performance. Although subjects encode highly detailed information about specific instances, they use different aspects of this information to accomplish different task-specific demands.     

Distortions in immediate memory

A series of five pairs of abstract geometrical figures were presented to each subject. Unknown to the subjects, the members of each pair were identical. The second member was presented 10 seconds after the first member and the subject then judged whether a specified feature of the figure had changed in one of two possible directions. One group of 32 subjects were not told which feature of the figure would be critical until presentation of the second member: a further group of 32 subjects were given this information before presentation of the first member. Subjects in both groups were significantly consistent with one another in some of their judgements, thus indicating that distortions in remembering had occurred. It is argued that memory distortions of this type (for which previous evidence has been unsatisfactory) are of particular interest since, unlike other memory changes, they are difficult to ascribe to the constructive or inferential character of recognition and recall.     

Interference in immediate spatial memory

It has been suggested that maintenance in visuospatial immediate memory involves implicit motor processes that are analogous to the articulatory loop in verbal memory. An alternative account, which is explored here, is that maintenance is based on shifts of spatial attention. In four experiments, subjects recalled spatial memory span items after an interval, and in a fifth experiment, digit span was recalled after an interval. The tasks carried out during the interval included touching visual targets, repeating heard words, listening to tones from spatially sepa-rated locations, pointing to these tones, pointing to visual targets, and categorizing spatial tar-gets as being from the left or right. Spatial span recall was impaired if subjects saw visual tar-gets or heard tones, and this impairment was increased if either a motor response or a categorical response was made. Repeating words heard in different spatial locations did not impair recall, but reading visually presented words did interfere. For digit span only, the tasks involving a verbal response impaired recall. The results are interpreted within a framework in which active spatial attention is involved in maintaining spatial items in order in memory, and is interfered with by any task (visual, auditory, perceptual, motor) that also makes demands on spatial attention.     

Selection in visual immediate memory

The sampling (partial report) technique of Sperling (1960) was used to study the efficiency of selection of letters from visual immediate memory (sensory storage). Selection by location, chromatic colour, achromatic colour, and size was fairly efficient whereas selection by orientation was difficult. Some parallels between selection in visual immediate memory and selective listening are briefly discussed.     

A note on immediate memory

In the course of an extensive inquiry into verbal memory processes (Gomulicki, 1952), some data were collected which appear to throw fresh light on the nature of immediate memory. In particular, it was found that many of the varieties of constructive change defined by Bartlett (1932) in connexion with long-term recall could be traced in the immediate reproduction of passages so brief as barely to exceed the memory-span. As changes of this nature do not appear to have been previously described in connexion with short-term recall some illustrative extracts from our material will be given. A full analysis along somewhat different lines has been presented elsewhere (Gomulicki, 1952).

In Gomulicki's experiments, narratives varying in length between 15 and 200 words were read aloud to 50 subjects, who were required to reproduce each passage orally as accurately as possible immediately after it had been read. The subjects (of whom half were women) were University graduates and undergraduates aged between 20 and 30. All subjects were tested individually and their reproductions recorded verbatim. In the present note, we shall be concerned only with the results given in the case of two passages, respectively 22 and 44 words in length. Despite their brevity, striking and consistent changes were observed in the reproductions which merit brief analysis.     

Auditory recency in immediate memory

Six experiments investigated the locus of the recency effect in immediate serial recall. Previous research has shown much larger recency for speech as compared to non-speech sounds. We compared two hypotheses: (1) speech sounds are processed differently from non-speech sounds (e.g. Liberman & Mattingly, 1985); and (2) speech sounds are more familiar and more discriminable than non-speech sounds (e.g. Nairne, 1988, 1990). In Experiments 1 and 2 we determined that merely varying the label given to the sets of stimuli (speech or non-speech) had no effect on recency or overall recall. We varied the familiarity of the stimuli by using highly trained musicians as subjects (Experiments 3 and 4) and by instructing subjects to attend to an unpracticed dimension of speech (Experiment 6). Discriminability was manipulated by varying the acoustic complexity of the stimuli (Experiments 3, 5, and 6) or the pitch distance between the stimuli (Experiment 4). Although manipulations of discriminability and familiarity affected overall level of recall greatly, in no case did discriminability or familiarity alone significantly enhance recency. What seems to make a difference in the occurrence of convincing recency is whether the items being remembered are undegraded speech sounds.     

Binocular rivalry and immediate memory

Three experiments examine features of a simple memory task on which right-handed, right eye dominant subjects have been reported to recall digits projected to the right eye more accurately than those projected simultaneously to the left eye. Superior recall by these subjects of information projected to the right eye was observed only when stimuli projected simultaneously to both eyes were seen as overlapped in the binocular percept. Under monocular presentations, accurracy of recall was not related to the eye with which stimuli were viewed. The binocular oveslap condition has a significance other than that of simply increasing the difficulty of identifying the elements in a visual display for there were no differences in accuracy of recall from each eye when overlapped stimuli were viewed monocularly. More accurate recall of right eye information appears to reflect the resolution of a conflict between inputs from each eye. The possible relation of this finding to cerebral dominance is also discussed. Order of recall in these experiments depended mainly on spatial cues provided by the experimental situation.     

A feature model of immediate memory

A feature model of immediate memory is presented, and simulations are described. List items are characterized as multiattribute vectors that can be selectively overwritten by subsequent external events and by the ongoing stream of internal activity. Degraded primary memory vectors are compared with intact secondary memory vectors, and retrieval likelihood is computed as the ratio of similarities. The model is shown to account for the major modality-based phenomena of the immediate serial recall literature, including modality-based temporal grouping effects and the negative effects of phonological similarity.     

The TECO theory and lawful dependency in successive episodic memory tests.

A large number of experiments in successive tests of episodic memory have focused on an experimental paradigm called recognition failure of recallable words. In this paradigm, a cued recall test follows a recognition test. Large amounts of data have revealed a lawful moderate dependence between recognition and cued recall. TECO (Sikstr?m, 1996b), a general connectionist theory of memory, has been applied for the phenomenon of recognition failure. This paper makes a strong claim that all possible pairwise combinations of successive tests between recognition, cued recognition, cued recall, and free recall follow a lawful relationship. The quantitative degree of the dependency predicted between these tests can be summarized in one function. Four experiments were conducted to test this claim. In line with the predictions, the results show that all pairwise combinations of these tests fit reasonably well with the proposed function. The TECO theory suggests theoretical insights into how recognition and recall may be divided into a recollection component, a familiarity component, and a cue-target integration component.     

Visual memory decay is deterministic

After observers see an object or pattern, their visual memory of what they have seen decays slowly over time. Nearly all current theories of vision assume that decay of short-term memory occurs because visual representations are progressively and randomly corrupted as time passes. We tested this assumption using psychophysical noise-masking methods, and we found that visual memory decays in a completely deterministic fashion. This surprising finding challenges current ideas about visual memory and sets a goal for future memory research: to characterize the deterministic "forgetting function" that describes how memories decay over time.     

Trace resistance and the decay of long-term memory

A theory of storage in long-term memory is described which characterizes the trace by two properties: strength and resistance. The theory makes four assumptions: (a) The rate of decay of strength equals the force on the trace divided by the resistance. (b) Force is proportional to trace strength and to the similarity of current traces to the previously established trace. (c) Resistance increases as the square root of trace age. (d) The resistance of a trace transfers completely to subsequent increments. The theory accounts for long-term retention functions over delays from 1 min to 2 yr, long retrograde amnesia, unlearning, effects of multiple learning trials and spacing of practice, and possibly recency judgments and retention functions following relearning.     

Functional decay of memory for tasks

Correct performance often depends on remembering the task one has been instructed to do. When the task periodically changes, memory for the current task must decay (lose activation) to prevent it from interfering with memory for the next task when that is encoded. Three task-switching experiments examine this decay process. Each shows within-run slowing, a performance decline occurring as memory for the current task decays. In experiment 1, slowing is attenuated when memory for the task is optional, suggesting that memory is indeed causal. Experiment 2 finds slowing despite a flat hazard rate for task instructions, suggesting that slowing is not an artifact of instruction anticipation. Experiment 3 finds slowing in the familiar alternating-runs paradigm (Rogers & Monsell, 1995), suggesting that it may lurk elsewhere. A process model of activation explains within-run slowing and relates it to switch cost and "restart cost" (Allport & Wylie, 2000) in functional terms.