Dynamic search and working memory in social recall

What are the mechanisms underlying search in social memory (e.g., remembering the people one knows)? Do the search mechanisms involve dynamic local-to-global transitions similar to semantic search, and are these transitions governed by the general control of attention, associated with working memory span? To find out, we asked participants to recall individuals from their personal social networks and measured each participant's working memory capacity. Additionally, participants provided social-category and contact-frequency information about the recalled individuals as well as information about the social proximity among the recalled individuals. On the basis of these data, we tested various computational models of memory search regarding their ability to account for the patterns in which participants recalled from social memory. Although recall patterns showed clustering based on social categories, models assuming dynamic transitions between representations cued by social proximity and frequency information predicted participants' recall patterns best-no additional explanatory power was gained from social-category information. Moreover, individual differences in the time between transitions were positively correlated with differences in working memory capacity. These results highlight the role of social proximity in structuring social memory and elucidate the role of working memory for maintaining search criteria during search within that structure.     

The Role of Semantic Clustering in Optimal Memory Foraging

Recent studies of semantic memory have investigated two theories of optimal search adopted from the animal foraging literature: Lévy flights and marginal value theorem. Each theory makes different simplifying assumptions and addresses different findings in search behaviors. In this study, an experiment is conducted to test whether clustering in semantic memory may play a role in evidence for both theories. Labeled magnets and a whiteboard were used to elicit spatial representations of semantic knowledge about animals. Category recall sequences from a separate experiment were used to trace search paths over the spatial representations of animal knowledge. Results showed that spatial distances between animal names arranged on the whiteboard were correlated with inter‐response intervals (IRIs) during category recall, and distributions of both dependent measures approximated inverse power laws associated with Lévy flights. In addition, IRIs were relatively shorter when paths first entered animal clusters, and longer when they exited clusters, which is consistent with marginal value theorem. In conclusion, area‐restricted searches over clustered semantic spaces may account for two different patterns of results interpreted as supporting two different theories of optimal memory foraging.     

Associative memory or algorithmic search: a comparative study on learning strategies of bats and shrews

Two common strategies for successful foraging are learning to associate specific sensory cues with patches of prey ("associative learning") and using set decision-making rules to systematically scan for prey ("algorithmic search"). We investigated whether an animal's life history affects which of these two foraging strategies it is likely to use. Natterer's bats (Myotis nattereri) have slow life-history traits and we predicted they would be more likely to use associative learning. Common shrews (Sorex araneus) have fast life-history traits and we predicted that they would rely more heavily on routine-based search. Apart from their marked differences in life-history traits, these two mammals are similar in body size, brain weight, habitat, and diet. We assessed foraging strategy, associative learning ability, and retention time with a four-arm maze; one arm contained a food reward and was marked with four sensory stimuli. Bats and shrews differed significantly in their foraging strategies. Most bats learned to associate the sensory stimuli with the reward and remembered this association over time. Most shrews searched the maze using consistent decision-making rules, but did not learn or remember the association. We discuss these results in terms of life-history traits and other key differences between these species. Our results suggest a link between an animal's life-history strategy and its use of associative learning.     

Simple Threshold Rules Solve Explore/Exploit Trade-offs in a Resource Accumulation Search Task

How, and how well, do people switch between exploration and exploitation to search for and accumulate resources? We study the decision processes underlying such exploration/exploitation trade-offs using a novel card selection task that captures the common situation of searching among multiple resources (e.g., jobs) that can be exploited without depleting. With experience, participants learn to switch appropriately between exploration and exploitation and approach optimal performance. We model participants' behavior on this task with random, threshold, and sampling strategies, and find that a linear decreasing threshold rule best fits participants' results. Further evidence that participants use decreasing threshold-based strategies comes from reaction time differences between exploration and exploitation; however, participants themselves report non-decreasing thresholds. Decreasing threshold strategies that “front-load” exploration and switch quickly to exploitation are particularly effective in resource accumulation tasks, in contrast to optimal stopping problems like the Secretary Problem requiring longer exploration.     

Comparing Locomotion With Lever-press Travel In An Operant Simulation Of Foraging

An operant model of foraging was studied. Rats searched for food by pressing on the left lever, the patch, which provided one, two, or eight reinforcers before extinction (i.e., zero reinforcers). Obtaining each reinforcer lowered the probability of receiving another reinforcer, simulating patch depletion. Rats traveled to another patch by pressing the right lever, which restored reinforcer availability to the left lever. Travel requirement changed by varying the probability of reset for presses on the right lever; in one condition, additional locomotion was required. That is, rats ran 260 cm from the left to the right lever, made one response on the right lever, and ran back to a fresh patch on the left lever. Another condition added three hurdles to the 260-cm path. The lever-pressing and simple locomotion conditions generated equivalent travel times. Adding the hurdles produced longer times in patches than did the lever-pressing and simple locomotion requirements. The results contradict some models of optimal foraging but are in keeping with McNair's (1982) optimal giving-up time model and add to the growing body of evidence that different environments may produce different foraging strategies.     

Search in external and internal spaces: evidence for generalized cognitive search processes

ABSTRACT— There is compelling molecular and behavioral evidence that goal-directed cognition is an evolutionary descendant of spatial-foraging behavior. Across animal species, similar dopaminergic processes modulate between exploratory and exploitative foraging behaviors and control attention. Consequently, we hypothesized that spatial-foraging activity could prime attentional cognitive activity. We examined how searching in physical space influences subsequent search in abstract cognitive space by presenting participants with a spatial-foraging task followed by a repeated Scrabble task involving search for words that could be made from letter sets. Participants who searched through clumpier distributions in space behaved as if words were more densely clumped in the Scrabble task. This was not a function of arousal, but was consistent with predictions of optimal-foraging theory. Furthermore, individual differences in exploratory search were conserved across the two types of tasks. Along with the biological evidence, our results support the idea that there are generalized cognitive search processes.     

A bayesian optimal foraging model of human visual search

Real-world visual searches often contain a variable and unknown number of targets. Such searches present difficult metacognitive challenges, as searchers must decide when to stop looking for additional targets, which results in high miss rates in multiple-target searches. In the study reported here, we quantified human strategies in multiple-target search via an ecological optimal foraging model and investigated whether searchers adapt their strategies to complex target-distribution statistics. Separate groups of individuals searched displays with the number of targets per trial sampled from different geometric distributions but with the same overall target prevalence. As predicted by optimal foraging theory, results showed that individuals searched longer when they expected more targets to be present and adjusted their expectations on-line during each search by taking into account the higher-order, across-trial target distributions. However, compared with modeled ideal observers, participants systematically responded as if the target distribution were more uniform than it was, which suggests that training could improve multiple-target search performance.     

Evidence against integration of spatial maps in humans: generality across real and virtual environments

A real-world open-field search task was implemented with humans as an analogue of Blaisdell and Cook’s (Anim Cogn 8:7–16, 2005) pigeon foraging task and Sturz, Bodily, and Katz’s (Anim Cogn 9:207–217, 2006) human virtual foraging task to 1) determine whether humans were capable of integrating independently learned spatial maps and 2) make explicit comparisons of mechanisms used by humans to navigate real and virtual environments. Participants searched for a hidden goal located in one of 16 bins arranged in a 4 × 4 grid. In Phase 1, the goal was hidden between two landmarks (blue T and red L). In Phase 2, the goal was hidden to the left and in front of a single landmark (blue T). Following training, goal-absent trials were conducted in which the red L from Phase 1 was presented alone. Bin choices during goal-absent trials assessed participants’ strategies: association (from Phase 1), generalization (from Phase 2), or integration (combination of Phase 1 and 2). Results were inconsistent with those obtained with pigeons but were consistent with those obtained with humans in a virtual environment. Specifically, during testing, participants did not integrate independently learned spatial maps but used a generalization strategy followed by a shift in search behavior away from the test landmark. These results were confirmed by a control condition in which a novel landmark was presented during testing. Results are consistent with the bulk of recent findings suggesting the use of alternative navigational strategies to cognitive mapping. Results also add to a growing body of literature suggesting that virtual environment approaches to the study of spatial learning and memory have external validity and that spatial mechanisms used by human participants in navigating virtual environments are similar to those used in navigating real-world environments.     

Memory of psychodiagnostic information: biases and effects of expertise

Problem-solving expertise has been associated with enhanced memory of domain-specific information. This enhanced memory is thought to play an important role in expert decisions. Meanwhile, research on psychodiagnostic decision making has found consistent limitations in experienced clinicians' ability to make optimal decisions. To what extent are these limitations associated with suboptimal memory processes? We compared memories of expert clinicians and novice graduate students for information learned while viewing a videotaped psychodiagnostic interview. Results of 3 tests suggest that expert clinicians exhibit enhanced memory that is flexible, selective, and accurate but with limitations that might contribute to poor decisions. Experts exhibited superior memory of personal criteria and disconfirmatory information. However, a framing manipulation induced performance in experts consistent with suboptimal decision making, and both groups needed exhaustive prompts for optimal memory search. Implications of these findings for expertise models are discussed.     

Implications of search accuracy for serial self-terminating models of search

In two experiments, the data from a total of 35 participants was compared to predictions from two competing serial search models, one with perfect memory and one with no memory. Reaction times were collected from an unlimited exposure duration, 4-alternative, target identification search task with array sizes of 8, 12, or 16 items. From the linear function relating RT to number of distractors a hypothetical “inspection time/item” was computed under the assumption of SSTS. Target identification accuracy was obtained from the same participants using the same displays, but with pre- and post-masks used to limit total inspection time (to 120, 180, 300, and 540 ms). Neither the memoryful nor memoryless model provided a good enough fit to the data to support the assumption that serial inspection is the primary process determining search time. Despite direct evidence for serial allocation of attention in visual search, these results suggest that scholars should seriously consider the possibility of hybrid search models in which serial and parallel strategies operate jointly.     

Dynamic links between memory and functional limitations in old age: longitudinal evidence for age-based structural dynamics from the AHEAD study

This study examined competing substantive hypotheses about dynamic (i.e., time-ordered) links between memory and functional limitations in old age. We applied the Bivariate Dual Change Score Model to 13-year longitudinal data from the Asset and Health Dynamics Among the Oldest Old Study (AHEAD; N = 6,990; ages 70 - 95). Results revealed that better memory predicted shallower increases in functional limitations. Little evidence was found for the opposite direction that functional limitations predict ensuing changes in memory. Spline models indicated that dynamic associations between memory and functional limitations were substantively similar between participants aged 70-79 and those aged 80-95. Potential covariates (gender, education, health conditions, and depressive symptoms) did not account for these differential lead-lag associations. Applying a multivariate approach, our results suggest that late-life developments in two key components of successful aging are intrinsically interrelated. Our discussion focuses on possible mechanisms why cognitive functioning may serve as a source of age-related changes in health both among the young-old and the old-old.     

Feeling the ease: How the use of oral motor fluency changes in amnesia

The present study examined the evolution observed in amnesic patients’ use of motor fluency when making recognition memory decisions. In this experiment, 9 patients with amnesia and 18 matched controls were presented with two recognition memory tasks composed of 3 types of items: (1) natural words, (2) nonwords difficult to pronounce, and (3) nonwords easy to pronounce, the latter having been shown to be processed in a surprisingly fluent manner as long as participants can articulate them at a subvocal level (i.e., oral motor fluency). Our results provide evidence that the motor-movement manipulation was successful to induce a fluency effect. More specifically, data revealed that both amnesic patients and control participants showed a pattern of response consistent with the use of fluency as a cue to memory for studied items. However, only control participants relied on fluency to increase their rate of “yes” responses for unstudied items. These results suggest that patients with amnesia set a more conservative response criterion before relying on oral motor fluency, showing a pattern consistent with the idea that fluency is only used as a cue to memory when it exceeds a certain threshold. These findings are discussed in terms of adaptative metacognition strategies implemented by amnesic patients to reduce fluency-based memory errors as well as in terms of the variations that seem to occur in these strategies depending on the type of fluency that is experienced.     

Verbalization of Decision Strategies in Multiple‐Cue Probabilistic Inference

In multiple‐cue probabilistic inference, people choose between alternatives based on several cues, each of which is differentially associated with an alternative's overall value. Various strategies have been proposed for probabilistic inference (e.g., weighted additive, tally, and take‐the‐best). These strategies differ in how many cue values they require to enact and in how they weight each cue. Do decision makers actually use any of these strategies? Ways to investigate this question include analyzing people's choices and the cues that they reveal. However, different strategies often predict the same decisions, and search behavior says nothing about whether or how people use the information that they acquire. In this research, we attempt to elucidate which strategies participants use in a multiple‐cue probabilistic inference task by examining verbal protocols, a high‐density source of process data. The promise of verbal data is in their utility for testing detailed information processing models. To that end, we apply protocol analysis in conjunction with computational simulations. We find converging evidence across outcome measures, search measures, and verbal reports that most participants use simplifying heuristics, namely take‐the‐best. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamic states in working memory modulate guidance of visual attention: Evidence from an n-back paradigm

Items held in working memory (WM) can automatically bias attention when they reappear in visual displays. Recent evidence, however, suggests that WM biases of attention may be reduced under certain conditions, for example with increasing memory load. We employed a dual task paradigm to investigate how WM biases are affected by dynamic updating of memory contents. 1-back and 2-back versions of a memory task with colour stimuli were interrupted at intervals by an unrelated visual search task. Reappearance in the search display of the item that was currently active in WM guided attention, while suppressed or inactive items did not. We conclude that the rapid updating of memory contents facilitates the shifting of memory representations into different activity states on a moment-to-moment basis. The finding is consistent with models that propose that only one item can be “active” in WM at any one time to guide attention.     

The privileged role of location in visual working memory

Reports have conflicted about the possible special role of location in visual working memory (WM). One important question is: Do we maintain the locations of objects in WM even when they are irrelevant to the task at hand? Here we used a continuous response scale to study the types of reporting errors that participants make when objects are presented at the same or at different locations in space. When several objects successively shared the same location, participants exhibited a higher tendency to report features of the wrong object in memory; that is, they responded with features that belonged to objects retained in memory but not probed at retrieval. On the other hand, a similar effect was not observed when objects shared a nonspatial feature, such as color. Furthermore, the effect of location on reporting errors was present even when its manipulation was orthogonal to the task at hand. These findings are consistent with the view that binding together different nonspatial features of an object in memory might be mediated through an object’s location. Hence, spatial location may have a privileged role in WM. The relevance of these findings to conceptual models, as well as to neural accounts of visual WM, is discussed.     

Resilience in the face of romantic rejection: The automatic impulse to trust

Can heeding the automatic impulse to trust one's romantic partner increase physical and psychological resilience in the face of doubts about a partner's responsiveness? Experimental participants were led to believe that their partner perceived a long list of faults in them. All participants then gave a speech about their future career goals while their partner watched. The results revealed impulsive trust (i.e., evaluative associations to the partner on the Implicit Associations Test) increased resilience to partner-criticism for people who heed their automatic impulses (i.e., low in working memory capacity). Specifically, for people low in working memory capacity and high in impulsive trust, partner-criticism increased resilience relative to control participants (i.e., expecting a more approving partner reaction to their speech, cardiovascular reactivity consistent with a positive challenge response). In contrast, for people low in working memory capacity and low in impulsive trust, partner-criticism decreased resilience relative to control participants (i.e., expecting a more disapproving partner reaction, cardiovascular reactivity consistent with a negative threat response).     

Guided search through memory

In “hybrid” search, observers search a visual display for any of several targets held in memory. It is known that the contents of the memory set can guide visual search (e.g., if the memorized targets are all animals, visual attention can be guided away from signs). It is not known if the visual display can guide memory search (e.g., if the memory set is composed of signs and animals, can a visual display of signs restrict memory search to just the signs?). In three hybrid search experiments, participants memorized sets of items that belonged to either one or several categories. Participants were then presented with visual displays containing multiple items, also drawn from one or several categories. Participants were asked to determine if any of the items from their current memory set were present in the visual display. We replicate the finding that visual search can be guided by the contents of memory. We find weaker, novel evidence that memory search can be guided by the contents of the visual display.     

编码方式对陌生字形记忆的影响

采用学习-再认范式,分别以韩字、英文假词为实验材料,考察了编码方式对陌生字形记忆的影响。在学习阶段,通过随机呈现整体和部分探测刺激,引导被试分别以整体编码和部分编码方式学习陌生字形,并在学习结束后一小时进行再认记忆测试。结果发现,无论以韩字还是以英文假词为材料,部分编码条件的记忆成绩均显著好于整体编码。该结果说明部分编码相比于整体编码能促进陌生字形记忆,并且这种优势效应具有跨文字系统的一致性。     

The role of memory and restricted context in repeated visual search

Previous studies have shown that the efficiency of visual search does not improve when participants search through the same unchanging display for hundreds of trials (repeated search), even though the participants have a clear memory of the search display. In this article, we ask two important questions. First, why do participants not use memory to help search the repeated display? Second, can context be introduced so that participants are able to guide their attention to the relevant repeated items? Experiments 1-4 show that participants choose not to use a memory strategy because, under these conditions, repeated memory search is actually less efficient than repeated visual search, even though the latter task is in itself relatively inefficient. However, when the visual search task is given context, so that only a subset of the items are ever pertinent, participants can learn to restrict their attention to the relevant stimuli (Experiments 5 and 6).     

An experimental analysis of optimal foraging behaviour in patchy environments

A series of experiments was designed to explore the cognitive mechanisms involved in optimal foraging models by using the behavioural controls of operant methodology. Rats were trained to press one of two levers to obtain reinforcement on a progressive variable-interval schedule, which modelled food patch depletion; the schedule was reset by pressing the other lever. Thus both duration (residence time in a patch) and rate-related (interval before and after the final reward) measures were obtained. Experiment 1, which manipulated environmental stability and quality, and Experiment 2, which varied travel time between patches, found results that supported the marginal value theorem (Charnov, 1976) and suggested that rats adjust capture rate to the environment average by monitoring the length of the interval between rewards. Experiment 3 modelled the clumping of food items and found that capture rate was now adjusted by adoption of a fixed giving-up time. Finally, Experiments 4a and 4b ruled out a time expectancy hypothesis by manipulating the number of food clumps and the series of inter-reinforcement intervals. Overall the experiments demonstrate the value of modelling foraging strategies in operant apparatus, and suggest that rats adopt rate predictive strategies when deciding to switch patches.