What’s the object of object working memory in infancy? Unraveling ‘what’ and ‘how many’

Infants have a bandwidth-limited object working memory (WM) that can both individuate and identify objects in a scene, (answering ‘how many?’ or ‘what?’, respectively). Studies of infants’ WM for objects have typically looked for limits on either ‘how many’ or ‘what’, yielding different estimates of infant capacity. Infants can keep track of about three individuals (regardless of identity), but appear to be much more limited in the number of specific identities they can recall. Why are the limits on ‘how many’ and ‘what’ different? Are the limits entirely separate, do they interact, or are they simply two different aspects of the same underlying limit?We sought to unravel these limits in a series of experiments which tested 9- and 12-month-olds’ WM for object identities under varying degrees of difficulty. In a violation-of-expectation looking-time task, we hid objects one at a time behind separate screens, and then probed infants’ WM for the shape identity of the penultimate object in the sequence. We manipulated the difficulty of the task by varying both the number of objects in hiding locations and the number of means by which infants could detect a shape change to the probed object. We found that 9-month-olds’ WM for identities was limited by the number of hiding locations: when the probed object was one of two objects hidden (one in each of two locations), 9-month-olds succeeded, and they did so even though they were given only one means to detect the change. However, when the probed object was one of three objects hidden (one in each of three locations), they failed, even when they were given two means to detect the shape change. Twelve-month-olds, by contrast, succeeded at the most difficult task level.Results show that WM for ‘how many’ and for ‘what’ are not entirely separate. Individuated objects are tracked relatively cheaply. Maintaining bindings between indexed objects and identifying featural information incurs a greater attentional/memory cost. This cost reduces with development. We conclude that infant WM supports a small number of featureless object representations that index the current locations of objects. These can have featural information bound to them, but only at substantial cost.     

Are awareness questionnaires valid? Investigating the use of posttest questionnaires for assessing awareness in implicit memory tests

Two experiments--one employing a perceptual implicit memory test and the other a conceptual implicit memory test--investigated the validity of posttest questionnaires for determining the incidence of awareness in implicit memory tests. In both experiments, a condition in which none of the studied words could be used as test responses (i.e., the none-studied condition) was compared with a standard implicit test condition. Results showed that reports of awareness on the posttest questionnaire were much less frequent in the none-studied condition than in the standard condition. This was especially true after deep processing at study. In both experiments, 83% of the participants in the none-studied condition stated they were unaware even though there were strong demands for claiming awareness. Although there was a small bias in the questionnaire (i.e., 17% of the participants in the none-studied condition stated they were aware), overall, there was strong support for the validity of awareness questionnaires.     

Selective storage and maintenance of an object’s features in visual working memory

It has been shown that we have a highly capacity-limited representational space with which to store objects in visual working memory. However, most objects are composed of multiple feature attributes, and it is unknown whether observers can voluntarily store a single attribute of an object without necessarily storing all of its remaining features. In this study, we used a masking paradigm to measure the efficiency of encoding, and neurophysiological recordings to directly measure visual working memory maintenance while subjects viewed multifeature objects and were required to remember only a single feature or all of the features of the objects. We found that measures of both encoding and maintenance varied systematically as a function of which object features were task relevant. These experiments show that individuals can control which features of an object are selectively stored in working memory.     

Working memory affects older adults’ use of context in spoken-word recognition

Many older listeners report difficulties in understanding speech in noisy situations. Working memory and other cognitive skills may modulate older listeners’ ability to use context information to alleviate the effects of noise on spoken-word recognition. In the present study, we investigated whether verbal working memory predicts older adults’ ability to immediately use context information in the recognition of words embedded in sentences, presented in different listening conditions. In a phoneme-monitoring task, older adults were asked to detect as fast and as accurately as possible target phonemes in sentences spoken by a target speaker. Target speech was presented without noise, with fluctuating speech-shaped noise, or with competing speech from a single distractor speaker. The gradient measure of contextual probability (derived from a separate offline rating study) affected the speed of recognition. Contextual facilitation was modulated by older listeners’ verbal working memory (measured with a backward digit span task) and age across listening conditions. Working memory and age, as well as hearing loss, were also the most consistent predictors of overall listening performance. Older listeners’ immediate benefit from context in spoken-word recognition thus relates to their ability to keep and update a semantic representation of the sentence content in working memory.     

Visual–spatial attention aids the maintenance of object representations in visual working memory

Theories have proposed that the maintenance of object representations in visual working memory is aided by a spatial rehearsal mechanism. In this study, we used two different approaches to test the hypothesis that overt and covert visual–spatial attention mechanisms contribute to the maintenance of object representations in visual working memory. First, we tracked observers’ eye movements while they remembered a variable number of objects during change-detection tasks. We observed that during the blank retention interval, participants spontaneously shifted gaze to the locations that the objects had occupied in the memory array. Next, we hypothesized that if attention mechanisms contribute to the maintenance of object representations, then drawing attention away from the object locations during the retention interval should impair object memory during these change-detection tasks. Supporting this prediction, we found that attending to the fixation point in anticipation of a brief probe stimulus during the retention interval reduced change-detection accuracy, even on the trials in which no probe occurred. These findings support models of working memory in which visual–spatial selection mechanisms contribute to the maintenance of object representations.     

Gorillas’ (Gorilla gorilla) use of experimenter-given manual and facial cues in an object-choice task

Several experiments have been performed to examine the great apes’ use of experimenter-given manual and visual cues in object-choice tasks. Considering their use of referential gestures in gaze-following paradigms, great apes perform surprisingly unsuccessfully in object-choice tasks. However, the large majority of object-choice experiments have been conducted with chimpanzees (Pan troglodytes) with very few experiments including other great ape species, making it difficult to generalize about the great apes. Interestingly, the only object-choice task conducted with gorillas (Gorilla gorilla) has indicated successful use of both manual and visual cues. It was the aim of the present study to gather more data on gorillas’ use of human manual and facial cues on the object-choice task. Gorilla subjects in this study did not show consistent use of three types of referential cues.     

On the role of rarity information in speakers’ choice of frame

In this article, we examine conversational behaviors when people describe the outcomes of uncertain events. We propose a new hypothesis, frame choice based on rarity information, that is built on the basis of one prominent measure of informativeness (i.e., self-information). The hypothesis predicts that when speakers can choose one of two logically equivalent frames for describing the outcome of an uncertain event (e.g., the results of the roll of a die or a medical operation), they prefer the frame denoting an event that is known or perceived to be rare. Four experiments using frame choice tasks provide evidence that speakers’ choice of frame is explained well by the rarity hypothesis.     

Can dogs use vocal intonation as a social referencing cue in an object choice task?

Evidence from the literature indicates that dogs’ choices can be influenced by human-delivered social cues, such as pointing, and pointing combined with facial expression, intonation (i.e., rising and falling voice pitch), and/or words. The present study used an object choice task to investigate whether intonation conveys unique information in the absence of other salient cues. We removed facial expression cues and speech information by delivering cues with the experimenter’s back to the dog and by using nonword vocalizations. During each trial, the dog was presented with pairs of the following three vocal cues: Positive (happy-sounding), Negative (sad-sounding), and Breath (neutral control). In Experiment 1, where dogs received only these vocal cue pairings, dogs preferred the Positive intonation, and there was no difference in choice behavior between Negative or Breath. In Experiment 2, we included a point cue with one of the two vocal cues in each pairing. Here, dogs preferred containers receiving pointing cues as well as Negative intonation, and preference was greatest when both of these cues were presented together. Taken together, these findings indicate that dogs can indeed extract information from vocal intonation alone, and may use intonation as a social referencing cue. However, the effect of intonation on behavior appears to be strongly influenced by the presence of pointing, which is known to be a highly salient visual cue for dogs. It is possible that in the presence of a point cue, intonation may shift from informative to instructive.     

A survey of neuropsychologists’ use of validity tests with children and adolescents

A web-based survey of validity test use by North American neuropsychologists was conducted, with 282 participants meeting inclusion criteria. Respondents indicated that they use a median of one stand-alone performance validity test (PVT), one embedded PVT, and one symptom validity test (SVT) per pediatric assessment. The vast majority of respondents indicated they give at least one PVT (92%) and at least one SVT (88%) during each pediatric assessment. A meaningful difference in validity use (i.e., at least a medium effect size) was only found for those who engage in forensic work, with those clinicians giving more stand-alone PVTs than those who do not conduct forensic work. The most frequently used validity measures in pediatric assessments are presented, as are reasons participants reported for both using and not using validity tests. Limitations and qualitative comparisons to other surveys on validity test use with adults are discussed.     

The importance of working memory updating in the Prisoner’s dilemma

Successful cooperation requires that humans can flexibly adjust choices to their partner’s behaviour. This, in turn, presupposes a representation of a partner’s past decisions in working memory. The aim of the current study was to investigate the role of working memory processes in cooperation. For that purpose, we tested the effects of working memory updating (Experiment 1) and working memory maintenance demands (Experiments 2 and 3) on cooperative behaviour in the Prisoner’s dilemma game. We found that demands on updating, but not maintenance, of working memory contents impaired strategy use in the Prisoner’s dilemma. Thus, our data show that updating a partner’s past behaviour in working memory represents an important precondition for strategy use in cooperation.     

Does the use of dolls facilitate children's memory of visits to the doctor?

Age differences in children's recall of salient experiences have frequently been documented, but these findings have routinely been based on studies in which verbal interviews have been employed. Because verbal interview protocols may underestimate the memory of young children, the purpose of this research was to compare the effectiveness of such an interview with two alternative protocols that involved the use of a doll. Using these contrasting protocols, 3-and 5-year-old children were asked to remember the details of a routine physical examination. Neither doll protocol facilitated 3-year-olds' recall of the features of the check-up. In contrast, 5-year-olds who were asked to demonstrate with a doll what happened in their examination showed enhanced recall. The inclusion of a doll had no effect on older or younger children's provision of elaborative detail about their visits to the doctor. Various measures of individual differences (e. g. temperament, language skill) predicted some aspects of the children's recall and elaboration. The findings are discussed in terms of the cognitive skills necessary for effective use of dolls in the assessment process, and are related to problems associated with interviewing young children who are involved in legal proceedings.     

What's in a name for memory errors? Implications and ethical issues arising from the use of the term "false memory" for errors in memory for details

The term "false memories" has been used to refer to suggestibility experiments in which whole events are apparently confabulated and in media accounts of contested memories of childhood abuse. Since 1992 psychologists have increasingly used the term "false memory" when discussing memory errors for details, such as specific words within lists. Use of the term to refer to errors in details is a shift in language away from other terms used historically (e.g., "memory intrusions"). We empirically examine this shift in language and discuss implications of the new use of the term "false memories." Use of the term presents serious ethical challenges to the data-interpretation process by encouraging over-generalization and misapplication of research findings on word memory to social issues.     

What drives the organization of object knowledge in the brain?

Various forms of category-specificity have been described at both the cognitive and neural levels, inviting the inference that different semantic domains are processed by distinct, dedicated mechanisms. In this paper, we argue for an extension of a domain-specific interpretation to these phenomena that is based on network-level analyses of functional coupling among brain regions. On this view, domain-specificity in one region of the brain emerges because of innate connectivity with a network of regions that also process information about that domain. Recent findings are reviewed that converge with this framework, and a new direction is outlined for understanding the neural principles that shape the organization of conceptual knowledge.     

Does working memory training promote the use of strategies on untrained working memory tasks?

Adaptive computerized training has been associated with significant enhancements in untrained working memory tasks, but the nature of the cognitive changes that underpin these improvements are not yet fully understood. Here, we investigate the possibility that training stimulates the use of memory-related strategies. In a randomized controlled trial, participants completed four tests of working memory before receiving adaptive working memory training, nonadaptive working memory training with low memory loads, or no training. Open-ended interviews about strategy use were conducted after the administration of untrained working memory tasks at two time points. Those in the adaptive and nonadaptive groups completed the assessments before (T1) and after (T2) 10 training sessions. The no-training group completed the same set of tasks at T1 and T2, without any training between assessment points. Adaptive training was associated with selective improvements in untrained tests of working memory, accompanied by a significant increase in the use of a grouping strategy for visuospatial short-term memory and verbal working memory tasks. These results indicate that training-related improvements in working memory may be mediated by implicit and spontaneous changes in the use of strategies to subsegment sequences of information into groups for recall when the tasks used at test overlap with those used during training.     

Is visual short-term memory object based? Rejection of the “strong-object” hypothesis

Is the capacity of visual short-term memory (VSTM) limited by the number of objects or by the number of features? VSTM for objects with either one feature or two color features was tested. Results show that capacity was limited primarily by the number of colors to be memorized, not by the number of objects. This result held up with variations in color saturation, blocked or mixed conditions, duration of memory image, and absence or presence of verbal load. However, conjoining features into objects improved VSTM capacity when size-orientation and color-orientation conjunctions were tested. Nevertheless, the number of features still mattered. When feature heterogeneity was controlled, VSTM for conjoined objects was worse than VSTM for objects made of single features. Our results support a weak-object hypothesis of VSTM capacity that suggests that VSTM is limited by both the number of objects and the feature composition of those objects.     

The role of verbal memory in regressions during reading is modulated by the target word’s recency in memory

During reading, a number of eye movements are made backward, on words that have already been read. Recent evidence suggests that such eye movements, called regressions, are guided by memory. Several studies point to the role of spatial memory, but evidence for the role of verbal memory is more limited. In the present study, we examined the factors that modulate the role of verbal memory in regressions. Participants were required to make regressions on target words located in sentences displayed on one or two lines. Verbal interference was shown to affect regressions, but only when participants executed a regression on a word located in the first part of the sentence, irrespective of the number of lines on which the sentence was displayed. Experiments 2 and 3 showed that the effect of verbal interference on words located in the first part of the sentence disappeared when participants initiated the regression from the middle of the sentence. Our results suggest that verbal memory is recruited to guide regressions, but only for words read a longer time ago.