Similarity and binding in memory: Bound to be detrimental

The process of binding information from different modalities and sources into an object is ubiquitous in cognition and has been a problem for research and modelling efforts in psychology. This process has been considered by most researchers as necessarily always beneficial to memory. In the present study we provide evidence that binding can be detrimental through the propagation of vulnerabilities to interference. Phonologically similar and dissimilar letters were presented sequentially at different locations on a computer monitor. Participants had to recall either the letters in their order of presentation or the spatial locations at which the letters had appeared. Whether binding was encouraged or not—providing prior knowledge of which dimension to remember—phonological similarity had a detrimental effect on recall of locations. Such a finding poses a challenge to the view that binding is the panacea in enhancing memory capacity.     

Similarity and contrast in memory for relations

The paper reports four experiments concerned with memory for sets of categorically related or unrelated nouns, as a function of the extent to which initial processing focused on categorical or distinctive features of the nouns. The general finding is that distinctive features are valuable for later intracategory discrimination in recall and recognition, but categorical features are not, as judged by cued recall, recognition, measures of association between items, and categorical intrusion errors. A theoretical framework, based on the diagnostic value of features for various classifications, is offered as an account of the results.     

Similarity effects in visual working memory

Perceptual similarity is an important property of multiple stimuli. Its computation supports a wide range of cognitive functions, including reasoning, categorization, and memory recognition. It is important, therefore, to determine why previous research has found conflicting effects of inter-item similarity on visual working memory. Studies reporting a similarity advantage have used simple stimuli whose similarity varied along a featural continuum. Studies reporting a similarity disadvantage have used complex stimuli from either a single or multiple categories. To elucidate stimulus conditions for similarity effects in visual working memory, we tested memory for complex stimuli (faces) whose similarity varied along a morph continuum. Participants encoded 3 morphs generated from a single face identity in the similar condition, or 3 morphs generated from different face identities in the dissimilar condition. After a brief delay, a test face appeared at one of the encoding locations for participants to make a same/different judgment. Two experiments showed that similarity enhanced memory accuracy without changing the response criterion. These findings support previous computational models that incorporate featural variance as a component of working memory load. They delineate limitations of models that emphasize cortical resources or response decisions.     

Similarity and attraction effects in episodic memory judgments

In the decision-making literature, it is known that preferences between two options can be influenced in different ways by the introduction of a third option. We investigated whether such influences could be demonstrated when making decisions about qualitative aspects of episodic memories. In a baseline condition, participants were asked which of two dissimilar events they remembered more vividly: (A) a well-known Olympic victory, or (B) the death of a well-known public figure. In two further conditions, a third event was added: (C) an Olympic victory similar and competitive to A, or (D) an Olympic victory similar but inferior to A. With the addition of C, participants were less likely to choose A than B (similarity effect), whereas with the addition of D, they were more likely to choose A than B (attraction effect), suggesting that effects known in decision-making can be generalised to relative judgments about episodic memories.     

Similarity and inhibition in long-term memory: evidence for a two-factor theory

Recalling a past experience often requires the suppression of related memories that compete with the retrieval target, causing memory impairment known as retrieval-induced forgetting. Two experiments examined how retrieval-induced forgetting varies with the similarity of the competitor and the target item (target-competitor similarity) and with the similarity between the competitors themselves (competitor-competitor similarity). According to the pattern-suppression model (M. C. Anderson & B. A. Spellman, 1995), high target-competitor similarity should reduce impairment, whereas high competitor-competitor similarity should increase it. Both predictions were supported: Encoding target-competitor similarities not only eliminated retrieval-induced forgetting but also reversed it, whereas encoding competitor-competitor similarities increased impairment. The differing effects of target-competitor and competitor-competitor similarity may resolve conflicting results concerning the effects of similarity on inhibition.     

Similarity as an organising principle in short-term memory

Abstract

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.     

How to be proactive about interference: lessons from animal memory

Processes of proactive interference were explored using the pigeon as a model system of memory. This study shows that proactive interference extends back in time at least 16 trials (and as many minutes), revealing a continuum of interference and providing a framework for studying memory. Pigeons were tested in a delayed same/different task containing trial-unique pictures. On interference trials, sample pictures from previous trials reappeared as test pictures on different trials. Proactive-interference functions showed greatest interference from the most recent trial and with the longer of two delays (10 s vs. 1 s). These interference functions are accounted for by a time-estimation model based on signal detection theory. The model predicts that accuracy at test is determined solely by the ratio of the elapsed time since the offset of the current-trial sample to the elapsed time since the offset of the interfering sample. Implications for comparing memory of different species and different types of memory (e.g., familiarity vs. recollection) are discussed.     

Similarity judgments and recognition memory for some common spices

A group of subjects rated the similarities of all 55 pairs of 11 spices, Nonmetric multidimensional scaling of this judgment matrix indicated a single underlying dimension, interpretable as pleasantness. Short-term recognition memory for the same spices was tested in separate groups of subjects required to remember one, three, and five stimuli, respectively. Performance was best for the group remembering one stimulus, but was not affected by the number of stimuli preceding the correct stimulus in the test. The confusion matrix for the one-stimulus group, symmetrized by removal of a stimulus bias, showed a significant correlation with the judgment matrix.     

Context attributes in memory are bound to item information,but not to one another

In four experiments, we compared binding between item and context information with binding between different types of context information. Participants studied line drawings of common objects that appeared in both different colors and different locations. We explored the effects of reinstating one type of information on recognition memory for another type, and we also tested the participants’ ability to discriminate intact from rearranged pairings of two types of information. Results showed that different contextual dimensions (i.e., color and location) were bound to item information (i.e., object information), but not to each other.     

Grouping and binding in visual short-term memory

Findings of 2 experiments are reported that challenge the current understanding of visual short-term memory (VSTM). In both experiments, a single study display, containing 6 colored shapes, was presented briefly and then probed with a single colored shape. At stake is how VSTM retains a record of different objects that share common features: In the 1st experiment, 2 study items sometimes shared a common feature (either a shape or a color). The data revealed a color sharing effect, in which memory was much better for items that shared a common color than for items that did not. The 2nd experiment showed that the size of the color sharing effect depended on whether a single pair of items shared a common color or whether 2 pairs of items were so defined-memory for all items improved when 2 color groups were presented. In explaining performance, an account is advanced in which items compete for a fixed number of slots, but then memory recall for any given stored item is prone to error. A critical assumption is that items that share a common color are stored together in a slot as a chunk. The evidence provides further support for the idea that principles of perceptual organization may determine the manner in which items are stored in VSTM. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Location and binding in visual working memory

Visual working memory (VWM) wa sexplored separatelyfor features and for their binding. Features were better recognized when the probes retained the same binding as in the original display, but changing the locations had little effect overall. However, there were strong interactions of location with binding and with matching or new features, suggesting that, when objects are attended, features and locations are spontaneously integrated in VWM. Despite this, when the locations arechanged, features can also be accessed with little decrement, perhaps from separate feature maps. Bindings, on the other hand, are more vulnerable to location changes, suggesting that locations play a central role in the early maintenance and retrieval of bound objects as well as in their initial encoding, at least when verbal coding is prevented. The results qualify past claims about the separation of locations and objects in VWM.     

Similarity of encoding context does not influence resistance to memory impairment following misinformation

Several recent studies have shown that exposure to verbal misleading post-event information does not impair subjects' ability to retrieve originally seen details. Two experiments were conducted to test the hypothesis that subjects would be more susceptible to memory impairment if the original and misleading information were presented in similar contextual formats. The results showed that misleading information did not lead to memory impairment when both original and misleading information were presented in the context of slides (Experiment 1) or when both original and misleading information were presented in the context of narratives (Experiment 2). Furthermore, resistance to memory impairment was observed both at relatively low levels of memory for the original information (Experiment 1) and at relatively high levels of memory for the original information (Experiment 2). The implications of the present results for interference principles of forgetting are discussed.     

The right parahippocampal gyrus contributes to the formation and maintenance of bound information in working memory

Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed to integrate and hold information being entered or retrieved from episodic memory. Although the brain system supporting such an integrative buffer is still in debate, the medial temporal lobe appears to be a promising candidate for the maintenance of bound information. In the current work, binding was assessed by comparing two conditions in which participants had to retain three letters and three spatial locations presented either bound or separate. At the behavioral level, lower performance was found for bound information than for separate information. When contrasting the two conditions, activation in the right parahippocampal gyrus was greater for the encoding and maintenance of bound information. No activation was observed in the medial temporal lobe during the retrieval of bound information. Together, our results suggest that the parahippocampal gyrus may underlie the integrative and maintenance functions of the episodic buffer.     

Superior perception of phasic physiological arousal and the detrimental consequences of the conviction to be aroused on worrying and metacognitions in GAD

Although people suffering from generalized anxiety disorder (GAD) often report arousal symptoms, psychophysiological studies show no evidence of autonomic hyperarousal. Hypersensitivity toward and catastrophic interpretation of phasic arousal cues may explain this discrepancy. The authors tested (a) whether GAD sufferers perceive nonspecific skin conductance fluctuations (NSCFs), an indicator of phasic autonomic arousal, better than controls do and (b) whether the conviction to be aroused contributes to the maintenance of worrying and metacognitive beliefs about worrying. Thirty-three GAD sufferers and 34 healthy controls participated in 2 experiments. In Experiment 1, participants were asked to detect their own NSCFs during a signal detection task. GAD sufferers accurately detected more of their NSCFs than did controls, who tended to miss NSCFs. In Experiment 2, participants were instructed to relax following worry induction. While relaxing, they received nonveridical feedback indicating either arousal or relaxation. Arousal feedback conserved negative metacognitive beliefs regarding worrying and also maintained negative mood and worry exclusively in GAD participants. These findings suggest that superior perception of phasic arousal cues and their catastrophic misinterpretation increases worrying, negative metacognitive beliefs about worrying, and anxious mood in GAD.     

Content-context binding in verbal working memory updating: on-line and off-line effects

The role of content–context binding in working memory updating has received only marginal interest, despite its undoubted relevance for the updating process. In the classical updating paradigm, the main focus has been on the process of discarding information when new information is presented. Its efficacy has been determined by measurement of the accuracy of recalled, updated information. In the current study we measured the working memory updating process directly, employing a dynamic memory task composed of alternating sequences of learning, active maintenance and updating phases. Binding was manipulated by changing the type of updating (total or partial) and the strength of the perceptual connection between items. The on-line updating process and the off-line efficacy were separately analysed. Both on-line and off-line measures indicated that partial updating conditions, where the operation of updating content–context binding was required, were more demanding than both total updating conditions and memory and maintenance phases. Our results suggest that working memory updating can be identified not only as a process of substitution of information, but also as inhibition of no longer relevant information and, above all, as a binding updating.     

Sensory and conceptual representations in memory: Motor images that cannot be imaged

Summary The paper argues for a distinction between sensory-and conceptual-information storage in the human information-processing system. Conceptual information is characterized as meaningful and symbolic, while sensory information may exist in modality-bound form. Furthermore, it is assumed that sensory information does not contribute to conscious remembering and can be used only in data-driven process reptitions, which can be accompanied by a kind of vague or intuitive feeling. Accordingly, pure top-down and willingly controlled processing, such as free recall, should not have any access to sensory data. Empirical results from different research areas and from two experiments conducted by the authors are presented in this article to support these theoretical distinctions. The experiments were designed to separate a sensory-motor and a conceptual component in memory for two-digit numbers and two-letter items, when parts of the numbers or items were imaged or drawn on a tablet. The results of free recall and recognition are discussed in a theoretical framework which distinguishes sensory and conceptual information in memory.     

Feature memory and binding in young and older adults

Intact memory for complex events requires not only memory for particular features (e.g., item, location, color, size), but also intact cognitive processes for binding the features together. Binding provides the memorial experience that certain features belong together. The experiments presented here were designed to explicate these as potentially separable sources of age-associated changes in complex memory—namely, to investigate the possibility that age-related changes in memory for complex events arise from deficits in (1) memory for the kinds of information that comprise complex memories, (2) the processes necessary for binding this information into complex memories, or (3) both of these components. Young and older adults were presented with colored items located within an array. Relative to young adults, older adults had a specific and disproportionate deficit in recognition memory for location, but not for item or for color. Also, older adults consistently demonstrated poorer recognition memory for bound information, especially when all features were acquired intentionally. These feature and binding deficits separately contribute to what have been described as older adults’ context and source memory impairments.     

Working memory deficits can be overcome: Impacts of training and medication on working memory in children with ADHD

This study evaluated the impact of two interventions—a training program and stimulant medication—on working memory (WM) function in children with attention deficit hyperactivity disorder (ADHD). Twenty‐five children aged between 8 and 11 years participated in training that taxed WM skills to the limit for a minimum of 20 days, and completed other assessments of WM and IQ before and after training, and with and without prescribed drug treatment. While medication significantly improved visuo‐spatial memory performance, training led to substantial gains in all components of WM across untrained tasks. Training gains associated with the central executive persisted over a 6‐month period. IQ scores were unaffected by either intervention. These findings indicate that the WM impairments in children with ADHD can be differentially ameliorated by training and by stimulant medication. Copyright © 2009 John Wiley & Sons, Ltd.     

Similarity and categorization: from vision to touch

Even though human perceptual development relies on combining multiple modalities, most categorization studies so far have focused on the visual modality. To better understand the mechanisms underlying multisensory categorization, we analyzed visual and haptic perceptual spaces and compared them with human categorization behavior. As stimuli we used a three-dimensional object space of complex, parametrically-defined objects. First, we gathered similarity ratings for all objects and analyzed the perceptual spaces of both modalities using multidimensional scaling analysis. Next, we performed three different categorization tasks which are representative of every-day learning scenarios: in a fully unconstrained task, objects were freely categorized, in a semi-constrained task, exactly three groups had to be created, whereas in a constrained task, participants received three prototype objects and had to assign all other objects accordingly. We found that the haptic modality was on par with the visual modality both in recovering the topology of the physical space and in solving the categorization tasks. We also found that within-category similarity was consistently higher than across-category similarity for all categorization tasks and thus show how perceptual spaces based on similarity can explain visual and haptic object categorization. Our results suggest that both modalities employ similar processes in forming categories of complex objects.