Gaming has become one of the most common activities for children and adolescents, and it is therefore of interest to investigate effects of gaming on cognition and behavior. The present study investigates if gaming is related to working memory capacity (WMC) or inattentive symptoms. We distinguished between three categories: action games, strategy games and non-gamers. The present study hypothesized that games involving higher cognitive functions, such as strategy games, could have an enhancing effect on working memory. A total of 211 children (age 5-16) participated. Gaming and inattentive behaviour was measured through parental assessment. WMC was measured with one verbal and one visuospatial task. No relation between gaming and inattentional symptoms was found. Strategy gamers performed better on the visuospatial and the verbal WM-tasks, but more time spent playing strategy games was not associated with significantly higher WMC, which indicates that this finding could be due to self-selection rather than being an causal effect of playing.

Simultaneous interpretation is a cognitively demanding task involving concurrent listening and speaking in two languages. Successful performance in this task likely relies on a good working memory, which reflects a person’s ability to process and store information simultaneously. The present study used the theoretical construct of working memory to investigate the task of simultaneous interpretation. Twenty student interpreters at two different levels of training in interpreting and sixteen bilinguals with no training in interpreting, all of whom spoke Chinese as a first language and English as a second language, participated in this study. They were compared on their performance for two measures of working memory – reading span and digit span – and on a simultaneous interpretation task. In addition, a translation judgment task and proficiency self-evaluation measures were administered to explore if language proficiency mediates working memory in participants’ L1 (native language) and L2 (second language). This study also examined the relation between working memory and performance in simultaneous interpretation. Results showed that the student interpreters performed better than bilinguals on simultaneous interpretation. Advanced-level student interpreters also outperformed bilinguals on all language versions of the memory span tasks, though first-year student interpreters did not show higher working memory than the bilinguals. Further, performance in simultaneous interpretation was related to working memory in both L1 and L2. Based on the study’s findings, two years of training in interpreting seemed to have a positive effect on improving working memory, whereas one year of training in interpreting did not help to increase working memory. On the other hand, higher language proficiency did not result in high working memory but contributed to better performance in simultaneous interpretation. Working memory, it is concluded, is important but language proficiency in L1 and L2 assumes a more critical role in simultaneous interpretation performance.

The focus of the thesis is the investigation of the causal nature of the established association between rumination and that ability to resolve interference from task-irrelevant information, and prepotent responses. Rumination is a term used to refer to both unhelpful dwelling on negative moods and depressive symptoms (e.g., Nolen-Hoeksema, 1991), and repetitive intrusive thoughts around the theme of unresolved personal goals (Martin & Tesser, 1996). It has been proposed that rumination occupies working memory resources, thereby depleting cognitive control capabilities necessary for the performance of concurrent effortful tasks (Hartlage, Alloy, Vasquez, & Dykman, 1993; Hertel, 2004; Watkins & Brown, 2002). This model constitutes one possible account of the considerable data demonstrating an association between depressive rumination and deficits on tasks invoking inhibitory processes (Joormann, Yoon, & Gotlib, 2007). An inhibition construct is invoked to account for the empirical observation of interference; however there are few instances where inhibition is unambiguously driving interference (MacLeod, 2007). Moreover, there is evidence that inhibition is not a unitary construct (Friedman & Miyake, 2004). Five experiments manipulated rumination on depressive symptoms and on personal goals in dysphoric and unselected samples in order to test Watkins and Brown’s (2002) hypothesis that state rumination impairs interference control capabilities. The causal impact of state rumination was examined on interference control tasks that implicate different inhibitory sub-types: resistance to proactive interference from positive and negative material (Studies One, Two, and Five), and prepotent response inhibition on a go/no-go paradigm (Studies Three and Four). No evidence was found to support the prediction that state rumination about depressed mood (Studies One and Two) or on-going personal goal discrepancies (Study Five) causes difficulties resolving interference from irrelevant emotional material relative to non-ruminative control conditions in both dysphoric (Studies One and Two) and unselected (Study Five) samples. No evidence was found to support the prediction that state rumination about personal goal discrepancies impairs prepotent response inhibition relative to non-ruminative control conditions (Studies Three and Four). There was some tentative evidence to suggest that ruminating on personal goal discrepancies increased efficiency in holding a single goal active in working memory without reinforcement (Study Four). The implications of these findings for existing models of the causal nature of the relationship between rumination and interference control processes is discussed (Chapter Nine). It is concluded that models proposing a causal impact of state rumination on available working memory capacity are insufficient to fully account for the established association between the trait tendency to ruminate and increased susceptibility to interference from irrelevant material.

Working memory, or the ability to maintain and manipulate information such that it can be used to guide behavior, is known to be severely capacity limited, in most circumstances, to about 3-4 objects. Both infants and adults have the ability to surpass these limits by encoding to-be-remembered items in groups or collections, exploiting statistical regularities or conceptual information to devise more efficient coding schema. Despite progress made toward understanding continuities in working memory, little is known about how changes over development interact with the ability to employ maximally efficient mnemonic data structures. Paper 1 demonstrates that although adults can encode at most three mutually exclusive collections that accrue sequentially over time, they can circumvent this limit when items overlap in features (e.g. red and blue circles and triangles) and statistical regularities are introduced among collections defined by a single visual feature (e.g. most red items are triangular and not circular). Adults' performance suggests they are able to encode items from intersecting collections hierarchically and exploit statistical regularities among collections to reconstruct the numerosities of up to six collections in parallel, exemplifying how efficient coding can radically enhance working memory. Paper 2 demonstrates that young preschoolers can also represent three mutually exclusive collections that accrue in an intermixed fashion over time. Results show that the ability to surpass this capacity limit by hierarchically reorganizing collections and exploiting statistical regularities among them develops between the ages of three and seven. These results are discussed in the context of executive function development. Paper 3 provides evidence that computations of average size and orientation rely on qualitatively different processes with distinct developmental trajectories. Experiment 1 demonstrates that while the presence of additional identical elements in an array detrimentally impacts 6-month-olds' representations of element size, it improves the precision with which infants represent orientation. Experiment 2 demonstrates that performance is not affected when infants' attention is cued to a single item within arrays. These results are discussed in the context of the development of controlled attention. / Psychology

Several research studies have examined the link between working memory ability and behavior problems in youth. Research suggests that children with working memory deficits demonstrate lower levels of attention and higher levels of hyperactivity, physical aggression, and other behavior problems. The purpose of this research was to determine the effects of developmental trajectories of working memory on the developmental trajectories of behavior problems. Results suggested that developmental increases in working memory did not lead to developmental decreases in behavior problems. Results from this study suggested that internalizing and externalizing behavior problems increase over the course of childhood. Several variables did lead to developmental change in behavior problems in children. Children who had lower initial levels of working memory increased in internalizing behaviors less than children with higher initial working memory ability. Also, high socioeconomic status led to smaller increases in internalizing and externalizing behavior, high Peabody Picture Vocabulary Test (PPVT) scores led to larger increases in internalizing and externalizing behavior, and high PPVT scores led to larger decreases in inattentive and hyperactive behavior. Results are discussed in reference to current theories about working memory and behavior problems. / text

The segment of the population that is 65 years and older is undergoing rapid growth. With this growth, there is an increased need for speech-language pathologists (SLPs) to treat cognitive-communicative disorders, most of which are age-related disorders secondary to neurologic disease. To do this effectively, SLPs require an understanding of how healthy aging affects cognition, memory and sensory processing. Although the interactions between sensory and cognitive processing are increasingly being investigated, little attention has been paid to the relationship between modality of information presentation and language comprehension in aging. Language comprehension is affected by component processes such as memory span and processing abilities, but to date there has been no systematic investigation of the effect of presentation modality on the processing of linguistic information across a number of tasks ranging in complexity.The primary purpose of this study was to investigate the effects of presentation modality on language processing. The secondary purposes of the study were to determine whether age affected performance on language processing measures, and whether adults can accurately predict if their performance was better in either the auditory or visual presentation condition. The effects of presentation modality were evaluated on four dependent measures: a digit span task, a word span task, a complex span task and a procedural instruction processing task. The participants were 37 older adults and 41 younger adults, matched for years of education and estimated verbal IQ.Three notable findings emerged from the study. First, both young and older adults recalled more information when it was presented in the auditory modality, regardless of the task. Second, age effects were present on all measures. Third, individuals were generally inaccurate in predicting which modality would result in better processing. Implications for the evaluation and treatment of older adults are discussed.

Traumatic brain injury (TBI) is a leading cause of disability globally. Cognitive deficits represent the primary source of on-going disability in this population, yet the mechanisms of these deficits remain poorly understood. Here functional and diffusion-weighted imaging techniques were employed to characterize the mechanisms of neurofunctional change following TBI and their relationship to cognitive function. TBI subjects who had sustained moderate to severe brain injury, demonstrated good functional and neuropsychological recovery, and screened positive for diffuse axonal injury but negative for focal brain lesions were recruited for the project. TBI subjects and matched controls underwent structural, diffusion-weighted and functional MRI. The functional scanning paradigm consisted of a complex working memory task with both load and executive control manipulations. Study one demonstrated augmented functional engagement for TBI subjects relative to healthy controls associated with executive control processing but not maintenance operations within working memory. In study two, multivariate neuroimaging analyses demonstrated that activity within a network of bilateral prefrontal cortex (PFC) and posterior parietal regions was compensatory for task performance in the TBI sample. Functional connectivity analyses revealed that a common network of bilateral PFC regions was active in both groups during working memory performance, although this activity was behaviourally relevant at lower levels of task demand in TBI subjects relative to healthy controls. In study three, diffusion-imaging was used to characterize the impact of diffuse white matter pathology on these neurofunctional changes. Unexpectedly, decreased white matter integrity was not correlated with working memory performance following TBI. However, markers of white matter pathology did inversely correlate with the compensatory functional changes observed previously. These results implicate diffuse white matter pathology as a primary mechanism of functional brain change following TBI. Moreover, reactive neurofunctional changes appear to mediate the impact of diffuse injury following brain trauma, suggesting new avenues for neurorehabilitation in this population.

Traumatic brain injury (TBI) is a leading cause of disability globally. Cognitive deficits represent the primary source of on-going disability in this population, yet the mechanisms of these deficits remain poorly understood. Here functional and diffusion-weighted imaging techniques were employed to characterize the mechanisms of neurofunctional change following TBI and their relationship to cognitive function. TBI subjects who had sustained moderate to severe brain injury, demonstrated good functional and neuropsychological recovery, and screened positive for diffuse axonal injury but negative for focal brain lesions were recruited for the project. TBI subjects and matched controls underwent structural, diffusion-weighted and functional MRI. The functional scanning paradigm consisted of a complex working memory task with both load and executive control manipulations. Study one demonstrated augmented functional engagement for TBI subjects relative to healthy controls associated with executive control processing but not maintenance operations within working memory. In study two, multivariate neuroimaging analyses demonstrated that activity within a network of bilateral prefrontal cortex (PFC) and posterior parietal regions was compensatory for task performance in the TBI sample. Functional connectivity analyses revealed that a common network of bilateral PFC regions was active in both groups during working memory performance, although this activity was behaviourally relevant at lower levels of task demand in TBI subjects relative to healthy controls. In study three, diffusion-imaging was used to characterize the impact of diffuse white matter pathology on these neurofunctional changes. Unexpectedly, decreased white matter integrity was not correlated with working memory performance following TBI. However, markers of white matter pathology did inversely correlate with the compensatory functional changes observed previously. These results implicate diffuse white matter pathology as a primary mechanism of functional brain change following TBI. Moreover, reactive neurofunctional changes appear to mediate the impact of diffuse injury following brain trauma, suggesting new avenues for neurorehabilitation in this population.

Measures of working memory capacity are associated with performance on a variety of cognitive tasks. A number of recent studies have provided evidence that training working memory can lead to improvements in fluid intelligence and performance on other untrained tasks. However, many of these studies suffer from design limitations. The aim of this study was to investigate the effects of working memory training on measures of fluid intelligence, reasoning, working memory, and attentional control by comparing a training group with an active control group. The training group improved more than the active control group on some, but not all outcome measures. Differential improvement for the training group was observed on fluid intelligence, working memory capacity, and response times on conflict trials in the Stroop task. In addition, individual differences in pre-training fluid intelligence scores and initial performance on the training task explain some of the variance in outcome measure improvements.

Reading comprehension (RC) is a complex, dynamic process by which readers interact with text to construct meaning. It relies on word-level decoding and vocabulary skills, text-level skills such as inference, and general-purpose cognitive processes such as working memory (WM). Bridging inferences, which connect different parts of text to maintain semantic coherence, are necessary for comprehension. WM is thought to provide the mental workspace that allows readers to comprehend text, including making bridging inferences. This dissertation includes two studies that investigate related but unique questions regarding inference-making, WM, and RC in school aged children. The first study demonstrated that bridging inference making increased with age and was affected by text distance such that inferences across larger chunks of text were more difficult to make than those between adjacent sentences. Bridging inferences were also affected by knowledge domain such that affective inferences based on character goals, desires, or motivations were made correctly less often than were concrete inferences based on concrete, causal information. Semantic updating, an aspect of WM that involves efficiently revising the contents of WM, predicted variance in the far-concrete inferencing condition. Semantic reactivation, an aspect of WM that involves bringing previously processed information back into WM, predicted variance in the far inferencing conditions regardless of knowledge domain. The second study investigated the word-level and text-level skills and general purpose cognitive processes that support performance on three different standardized RC measures. Semantic updating and semantic reactivation predicted variance on the RC tool considered to measure mental model building (WJIII-PC, Woodcock-Johnson-III passage comprehension subtest). Semantic reactivation also predicted variance on the RC tool considered to measure the ability to build and then reflect upon the mental model (WIAT-II-RC, Wechsler Individual Test of Achievement reading comprehension subtest). A measure of verbal WM predicted performance on one RC measure in the presence of word-level and text-level skills but only when the hypothesized components of WM (updating and reactivation) were not included in the model. Additionally, bridging inference making uniquely predicted performance on all three RC measures. The findings suggest readers coordinate different cognitive processes depending on the comprehension task. / Social Sciences and Humanities Research Council of Canada (SSHRC)