Evidence for decay in verbal short-term memory: a commentary on Berman, Jonides, and Lewis (2009)

M. G. Berman, J. Jonides, and R. L. Lewis (2009) adapted the recent-probes task to investigate the causes of forgetting in short-term memory. In 7 experiments, they studied the persistence of memory traces by assessing the level of proactive interference generated by previous-trial items over a range of intertrial intervals. None of the experiments found a reduction in proactive interference over time, which they interpreted as evidence against time-based decay. However, it is possible that decay actually occurred over a shorter time period than was tested in this study, wherein the shortest decay interval was 3,300 ms. By reducing the time scale, the 2 experiments reported in the current commentary revealed a sharp decrease in proactive interference over time, with this reduction reaching a plateau in less than 3 s. This pattern suggests that decay operates in the early stages, whereas subsequent forgetting is likely to be due to interference.     

Proactive interference between cues trained with a common outcome in first-order Pavlovian conditioning

The nature of interference between cues (X, A) trained apart with a common outcome (O; an unconditioned stimulus) was explored by assessing proactive interference in first-order Pavlovian conditioning (i.e., A-O, X-O, resulting in attenuated responding to X). Three lick-suppression studies were conducted with water-deprived rats. Posttraining extinction of the interfering cue (A) attenuated proactive interference (Experiment 1), which mirrors the observation that extinction of the competing cue can reduce competition between cues trained together (e.g., recovery from overshadowing). Proactive interference was also attenuated with manipulations known to attenuate interference between outcomes trained apart (e.g., counterconditioning), namely reminder cues (Experiment 2) and renewal (Experiment 3). The findings suggest that similar processes underlie interference between cues trained apart, between cues trained together, and between outcomes trained apart.     

Retroactive and proactive interference effects in dual learning of blissymbolics and manual sign

Nonspeech systems can be either aided or unaided. Each system possesses its unique learning and memory characteristics. One instructional strategy designed to give learners the advantages of both systems is dual instruction in aided and unaided communication. One problem with this approach, however, might be that of retroactive and proactive interference in learning and memory. The current experiment investigated whether dual instruction in Blissymbolics and manual (ASL) sign would lead to retroactive and proactive interference. Lists of sign/symbol referents in the two systems were taught, to nonhandicapped adults in a controlled setting. No effects of retroactive or proactive interference were found. Additionally, a proactive facilitation effect was found for immediate retention. Results are discussed in terms of the nature of the task, the learning memory attributes of the nonspeech systems, and the effects of sign/symbol translucency.     

Interference Effects in Learning Similar Sequences of Discrete Movements

Three experiments were conducted to examine proactive and retroactive interference effects in learning 2 similar sequences of discrete movements. In each experiment, the participants in the experimental group practiced 2 movement sequences on consecutive days (1 on each day, order counterbalanced across participants) followed by retention tests on the third day. In all, 2 out of 8 target locations differed between the 2 sequences. Experiment 1 established the nature of the interference effects in the present setup. Clear evidence was found for button-specific proactive and retroactive interference effects. Experiments 2 and 3 further probed the mechanisms underlying those effects, by varying the numbers of repetitions (50 or 250) of the 1st and 2nd sequence (Experiment 2) and the hand, dominant or nondominant, with which the sequences were practiced (Experiment 3). Experiment 2 showed that after a mere 50 repetitions, the representation of the movement structure was strong enough to evoke the effects observed in Experiment 1. Experiment 3 revealed that learning with the dominant hand did not result in more pronounced interference effects compared with learning with the nondominant hand. In combination, these results suggest that changes in the representation of the movement structure are primarily responsible for the observed interference effects.     

Is Event-Based Prospective Memory Resistant to Proactive Interference?

Proactive interference builds up rapidly in recall with the presentation of successive lists comprising items from a single category (e.g., animals). In two experiments, we used a similar build-up paradigm in prospective memory. Interestingly, in Experiment 1, there was no evidence of proactive interference in prospective memory, although build-up emerged in a similar recall task. In Experiment 2, by also showing proactive interference build-up in a recognition task analogous to our prospective memory task, we ruled out the possibility that it was the recognition processes inherent in the prospective memory task that might make the task easier and prevent proactive interference. We suggest that, under normal conditions, prospective memory is resistant to build-up of proactive interference and propose that this resistance is a function of the strengthening afforded by a cue-to-intention association that is a part of prospective memory tasks. We discuss the finding using the classical paired-associate learning framework.     

The role of proactive interference in mnemonic techniques

The success of many mnemonic techniques, such as the method of loci, is based on the use of specific well-known anchors, which are mentally combined with to-be-learned items and subsequently facilitate their retrieval. In our studies we intended to answer the question of whether the repeated application of the method of loci may result in proactive interference effects, as might be expected due to the applied association of items with the same loci each time the method is used. To this end, we manipulated list similarity in a typical proactive interference design and compared the method of loci with the link method and the rehearsal method, which do not involve the use of a specified set of anchors. Our results replicate those from other studies, which have shown that the use of a mnemonic technique leads to superior recall of list items compared to a simple rehearsal strategy. We were further able to show that the repeated learning of items from different categories results in moderate practice effects over three list-learning trials, whereas this effect is superimposed by an effect of proactive interference if different lists are composed of items from the same category. However, this effect of proactive interference was not increased for the method of loci, and we discuss this finding with regard to its practical implications.     

Reducing Proactive Interference in Motor Tasks

Abstract

Changing automatized movement patterns often leads to initial performance decrements caused by proactive interference. In this study, we scrutinized whether proactive interference could be reduced by inhibiting the to-be-changed movement pattern by means of a physical movement constraint and verbal inhibition instructions, and whether any of the two interventions may be superior. Skilled typists typed short texts as fast and accurately as possible on a regular QWERTZ keyboard. After baseline measures, a new rule prohibiting the use of the left index finger was introduced. Subsequently, participants took part in either a verbal instruction or an additional motor restriction intervention phase. Results revealed that the original rule change was successful in inducing proactive interference in skilled typists. Most importantly, the two interventions similarly reduced proactive interference both immediately following the rule change and after ten practice sessions. We conclude that reducing proactive interference by means of physical motor restrictions and verbal instructions may be equally effective.     

Asymmetric interference effects in fragment completion: the consequences of recognition failures and successes

We examined the extent to which implicit and explicit memory performance is susceptible to the effects of proactive and retroactive interference produced by orthographic similarity. Participants studied target and nontarget words that were orthographically similar or dissimilar. At test, they were given fragments of the target words intermixed with fragments of nonstudied words. Participants' initial task was to determine whether each fragment was a studied word. If they recognized it, they were to complete the fragment with the studied word; if not, they were to complete the fragment with the first word that came to mind. Completion rates including both recognized and nonrecognized target fragments provided evidence of proactive but not retroactive interference. The implicit processing engaged by the nonrecognized target fragments was found to be the primary source of the proactive interference effect.     

Associative interference in Pavlovian conditioning: A function of similarity between the interfering and target associative structures

Three lever-press suppression studies were conducted with water-deprived rats to investigate the role of similarity in proactive interference within first-order Pavlovian conditioning. Experiments 1a and 1b assessed the influence of stimulus complexity in proactive interference. Both experiments found greater interference when the interfering cue and target cue were composed of the same number of elements. Experiment 2 assessed the influence of context similarity in proactive interference and demonstrated that stronger proactive interference occurred when the interfering cue and the target cue were trained in the same context. The results in conjunction with other reports indicate that various types of cue interaction (e.g., interference and competition) are influenced by similarity of the interacting training events.     

On the role of different subdimensions of inhibition for successful motor skill change

Modifying already automatized movement skills often causes proactive interference resulting in initial performance decrements. Dealing with interference is closely linked to inhibitory functions, since inhibition is needed to suppress automatic, but undesired behavior. The aim of this study was to investigate the role of three different inhibition dimensions for interference control in motor skill change. To this end, 42 participants performed three tests each measuring a different dimension of inhibition: resistance to distractor interference (Eriksen-Flanker Task), resistance to proactive interference (Brown-Peterson Variant) and prepotent response inhibition (Stop-Signal Task). To examine the amount of proactive interference in a motor skill change task, participants were then asked to type a short paragraph as fast and accurately as possible on a regular computer keyboard. After this baseline measure, in order to induce proactive interference, they were confronted with a manipulated keyboard on which the letters S and L were switched. This change led to an immediate performance decline, observable in increased typing times and errors. Results also showed that larger performance decrements were significantly associated with better baseline performance, lower scores on prepotent response inhibition and higher scores on resistance to distractor interference. Besides supporting the idea of inhibition as a multidimensional construct, these findings replicate and confirm recent research indicating that the success in motor skill change is predicted by the ability to suppress prepotent response tendencies.     

Proactive effects of memory in young and older adults: The role of change recollection

Age-related deficits in episodic memory are sometimes attributed to older adults being more susceptible to proactive interference. These deficits have been explained by impaired abilities to inhibit competing information and to recollect target information. In the present article, I propose that a change recollection deficit also contributes to age differences in proactive interference. Change recollection occurs when individuals can remember how information changed across episodes, and this counteracts proactive interference by preserving the temporal order of information. Three experiments were conducted to determine whether older adults are less likely to counteract proactive interference by recollecting change. Paired-associate learning paradigms with two lists of word pairs included pairs that repeated across lists, pairs that only appeared in List 2 (control items), and pairs with cues that repeated and responses that changed across lists. Young and older adults’ abilities to detect changed pairs in List 2 and to later recollect those changes at test were measured, along with cued recall of the List 2 responses and confidence in recall performance. Change recollection produced proactive facilitation in the recall of changed pairs, whereas the failure to recollect change resulted in proactive interference. Confidence judgments were sensitive to these effects. The critical finding was that older adults recollected change less than did young adults, and this partially explained older adults’ greater susceptibility to proactive interference. These findings have theoretical implications, showing that a change recollection deficit contributes to age-related deficits in episodic memory.     

Absence of adult age differences in forgetting in the Brown-Peterson Task

Despite some recent evidence to the contrary, no reliable age differences in proactive interference (PI) or retroactive interference (RI) were found in a cross-sectional study of adults aged 18-29 and 63-75. Individual memory span was used as the list length in the Brown-Peterson Task in order to achieve stimulus equivalence of memory loads across individuals and age groups. Data from rehearsers were excluded from the analyses in order to isolate age differences in passive forgetting processes from those in rehearsal. PI was manipulated by presenting categorized or uncategorized memory lists. RI was manipulated, holding distractor task difficulty constant, by using words or tones in a signal detection distractor task. It is concluded that age differences are minimal to nonexistent in passive RI-related processes such as decay and perturbation and in passive PI-related processes such as set effects in semantic encoding.     

Asymmetric interference in implicit memory: effects of study-test awareness and stimulus order

This study examined the extent to which fragment completion performance is susceptible to the effects of two different forms of interference (proactive and retroactive) and whether any of these effects depend on participants' awareness of the relationship between study and test. Unaware participants were found to be susceptible to proactive but not retroactive interference. Aware participants did not show evidence of susceptibility to either form of interference. These results contribute to the debate about whether implicit memory is immune to interference effects by demarcating the limits of such an immunity.     

Perceptual distinctiveness and proactive interference in the primacy effect

When subjects monitor a list of verbal items for one item which is to be selected and remembered, they are more likely to recall the critical item if it is the first member of the list than if it is presented towards the centre of the list. The present experiment examined the possibility that this primacy results from an accumulation of proactive interference from incidentally processed early members of the list which would cause a decrement in the recall of later members. By changing the semantic category of the list members before presentation of the critical item any accumulated interference would have been released, but this procedure produced no weakening of the primacy effect and so the interference theory of primacy was not supported. An alternative explanation of the effect was discussed in which it is assumed that the first member of a series is perceptually distinct from central members.     

Heterogeneous inhibition processes involved in different facets of self-reported impulsivity: evidence from a community sample

Whiteside and Lynam (Whiteside, S. P., & Lynam, D. R. (2001). The Five Factor Model and impulsivity: Using a structural model of personality to understand impulsivity. Personality and Individual Differences, 30, 669-689) clarified the multifaceted nature of impulsivity by identifying four distinct facets of self-reported impulsive behaviors: urgency, (lack of) premeditation, (lack of) perseverance, and sensation seeking. Building on work by Bechara and Van der Linden (Bechara, A., & Van der Linden, M. (2005). Decision-making and impulse control after frontal lobe injuries. Current Opinion in Neurology, 18, 734-739), the main objective of this study was to investigate the hypothesis that perseverance and urgency map onto the two distinct inhibitory functions distinguished by Friedman and Miyake (Friedman, N. P., & Miyake, A. (2004). The relations among inhibition and interference control functions: A latent-variable analysis. Journal of Experimental Psychology: General, 133, 101-135): prepotent response inhibition and resistance to proactive interference. Participants (N = 126) completed the UPPS Impulsive Behavior Scale and three tasks: a recent-negatives task to assess proactive interference in working memory, and two Go/No-Go tasks at different paces, the slower of which also assessed task-unrelated thoughts (TUTs). Consistent with the hypothesis, TUTs were positively correlated with lack of perseverance, and multiple regressions revealed that urgency was specifically related to errors in prepotent response inhibition, and lack of perseverance to errors due to difficulties overcoming proactive interference.     

Individual differences in digit span, susceptibility to proactive interference, and aptitude/achievement test scores

Individual differences in digit span, susceptibility to proactive interference, and various aptitude/achievement test scores were investigated in two experiments with adults. Susceptibility to proactive interference was estimated from performance in a position task in Experiment 1, and from the Brown-Peterson task in Experiment 2. In contrast to previous research, digit span was strongly correlated with many of the aptitude/achievement scores in both experiments, suggesting that the digit span task taps some important components of mental ability. The results of both experiments were also consistent in offering no support for the hypothesis that susceptibility to proactive interference is an important source of span differences. Finally, the results of Experiment 2 suggest that susceptibility to proactive interference is a source of individual differences in reading comprehension and knowledge of word meanings, but not in grammar and word usage skills, reading rate, or quantitative ability.     

Proactive interference, accessibility bias, and process dissociations: valid subjective reports of memory

Proactive interference was assessed with a variant of the process-dissociation procedure, which separates effects of habit (accessibility bias) and recollection (discriminability). In three cued-recall experiments, proactive interference was shown to be an effect of bias rather than an effect on actual remembering. Divided attention, age, and study duration selectively influenced the recollection parameter, whereas training probability selectively influenced the habit parameter. Furthermore, in Experiments 2 and 3, subjective reports of remembering were highly correlated with, and nearly identical to, objective estimates of recollection gained from the process-dissociation procedure. The authors discuss the relevance of the results to theories of proactive interference and argue that older adults' greater susceptibility to interference effects is sometimes caused by an inability to recollect rather than by an inability to inhibit a preponderant response.     

Implicit proactive interference, age, and automatic versus controlled retrieval strategies

We assessed the extent to which implicit proactive interference results from automatic versus controlled retrieval among younger and older adults. During a study phase, targets (e.g., "ALLERGY") either were or were not preceded by nontarget competitors (e.g., "ANALOGY"). After a filled interval, the participants were asked to complete word fragments, some of which cued studied words (e.g., "A_L_ _GY"). Retrieval strategies were identified by the difference in response speed between a phase containing fragments that cued only new words and a phase that included a mix of fragments cuing old and new words. Previous results were replicated: Proactive interference was found in implicit memory, and the negative effects were greater for older than for younger adults. Novel findings demonstrate two retrieval processes that contribute to interference: an automatic one that is age invariant and a controlled process that can reduce the magnitude of the automatic interference effects. The controlled process, however, is used effectively only by younger adults. This pattern of findings potentially explains age differences in susceptibility to proactive interference.     

Proactive control of proactive interference using the method of loci

Proactive interferencebuilds up with exposure to multiple lists of similar items with a resulting reduction in recall. This study examined the effectiveness of using a proactive strategy of the method of loci to reduce proactive interference in a list recall paradigm of categorically similar words. While all participants reported using some form of strategy to recall list words, this study demonstrated that young adults were able to proactively use the method of loci after 25 min of instruction to reduce proactive interference as compared with other personal spontaneous strategies. The implications of this study are that top-down proactive strategies such as the method of loci can significantly reduce proactive interference, and that the use of image and sequence or location are especially useful in this regard.     

The effects of ongoing activity on time estimation in prospective remembering

Two experiments examined whether time‐based prospective memory performance is influenced by the continuous or discontinuous nature of an ongoing activity. The first experiment demonstrated that prospective memory performance was not influenced by the engagement in continuous or discontinuous ongoing activity. The second experiment demonstrated that a discontinuous ongoing activity negatively affected prospective memory performance when participants had to execute two time‐based tasks for which the retention intervals partially overlapped. The results suggest that when individuals are engaged in multiple time‐based tasks, a general timing disruption occurs, with a proactive interference effect resulting in costs that are detrimental to prospective timing. Copyright © 2009 John Wiley & Sons, Ltd.