Melbourne School of Psychological Sciences - Theses
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ItemThe role of attention in subitizing( 2019)This thesis aimed to address a long-standing question: “Why are small numbers of items enumerated differently from large numbers of items?” (Trick & Pylyshyn, 1993, p. 331). Specifically, this thesis examined whether the processing of small sets requires attention processes and, if so, how attention plays a role in subitizing. Answers to this question are central to debates about the nature of contemporary models of numerical cognition. In this thesis, attention was manipulated in an enumeration task using the Posner Cueing paradigm. The physical properties of to-be-enumerated objects in the experiments were well-controlled. Different display times of objects were used in the experiments. An internal mini meta-analysis was run to synthesize the attention effects in these experiments. A meta-analysis was also conducted to evaluate the observed attention effects in previous studies. Moreover, to investigate how attention plays a role in the subitizing range, experiments was conducted to compare the attention effect between an enumeration task and a control task. Findings from the experiments reported in this thesis suggested a robust attention effect in the subitizing range: there was no dichotomy in attention between subitizing and counting. These findings imply that subitizing processing requires attention. The meta- analysis evaluating previous studies also suggested a robust attention effect in the subitizing range. Moreover, the findings reported in this thesis suggested that attention does not specifically affect numerical processing. Instead, attention played an important role in general cognitive processes in the subitizing range. A tentative model was proposed to explain the mechanisms underlying visual enumeration, especially in the subitizing range. In summary, these findings suggest that enumeration in the subitizing range requires attention. Specifically, attention is required for general processes in the subitizing range.
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ItemPragmatic language and theory of mind in children with symptoms of ADHD: relationships with executive functions( 2018)Children’s social, academic and interpersonal functioning is sustained by language in use, yet a moderate body of research indicates that children with ADHD, and children with ADHD symptoms, have problems with pragmatic language. They can be prone to excessive talking, poor conversational turn-taking and lack of clarity and coherence in their utterances. Pragmatic language is thought to depend in part on theory of mind (ToM) and on executive functions such as sustained attention and response inhibition. This research first investigates the nature and extent of pragmatic language problems in children with symptoms of ADHD, and any co-occurring problems with ToM. In view of neurocognitive heterogeneity in children with ADHD and in the general population, the research then examines whether pragmatic language problems are related to specific subgroups of executive function, and whether any ToM difficulties are similarly related. A community sample of 148 children aged 8 to 10 years participated (76 boys). ADHD symptoms and pragmatic language ability were assessed by parent questionnaire. Most of the children (n = 110, 57 boys) then completed the Sustained Attention to Response Task (SART; Robertson, Manly, Andrade, Baddeley, & Yiend, 1997) and a digit span task, while conversational pragmatics was assessed using observational ratings from a semi-structured conversation and ToM was assessed from children’s responses to an animated triangles task. Children with ADHD symptoms (n = 29) showed substantially poorer pragmatic language than children without such symptoms (n = 81), in terms of both parent report of communications skills and conversational pragmatics. They evinced subtle problems with ToM. Cluster analysis revealed three distinct profiles of performance on the SART, with one subgroup characterised by poor sustained attention (n = 13), one subgroup with poor response inhibition (n = 16) and the remainder with no particular weakness (n = 81). Children with ADHD symptoms were distributed across all three subgroups. Nonetheless, the subgroup with poor sustained attention had a higher level of ADHD symptoms and a consistent pattern of poorer conversational pragmatics and ToM than the subgroup that performed well on the SART. Surprisingly, the subgroup with poor response inhibition did not show poorer pragmatic language or ToM, nor higher level of ADHD symptoms, than the subgroup that performed well on the SART. The results indicate that neurocognitive heterogeneity amongst children with ADHD symptoms is nested within heterogeneity in the general population. Moreover, specific weakness in sustained attention may contribute to behavioural symptoms of ADHD and to problems with pragmatic language and ToM amongst a subgroup of school-aged children. Sustained attention may be required to monitor the communicative intentions of conversational partners and the content, timing and relevance of conversational turns. Executive weakness, however, does not appear to underlie ADHD symptoms or pragmatic language and ToM problems in all children, posing a challenge to causal models of ADHD. Results are discussed in terms of whether behavioural symptoms of ADHD might disrupt both interpersonal engagement and the application of executive functions in communicative contexts.
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ItemThe relationships between response time variability, brain signals, ADHD symptoms, and behavioural control( 2018)Individuals with Attention Deficit Hyperactivity Disorder (ADHD) often produce greater response time variability (RTV) when performing cognitive tasks. It is still unclear why increased RTV is observed in ADHD. One possible explanation for this is that individuals with ADHD may have aberrant patterns of brain connectivity, leading to inefficient communication between brain regions. Graph theoretical analysis is an approach used to characterise patterns of brain connectivity. This study aimed to investigate the relationship between brain connectivity, RTV, age, and levels of ADHD symptoms using a cross sectional design. Children aged 9-12 years and adolescents aged 15-18 years performed three tasks in this thesis - the Sustained Attention to Response Task (SART), the Flanker SART, and the Detection of Disappearance Task (DDT). EEG was recorded while participants performed the three tasks. The Conners 3 questionnaire was used to measure the participants' levels of ADHD symptoms. Multiple parameters were computed to reflect different aspects of RTV, using ex-Gaussian and the Fast Fourier Transform (FFT) techniques. Tau from the ex-Gaussian analysis reflects skewness and sigma reflects deviation of the Gaussian portion of the RT distribution. The FFT analysis allows an examination of periodic changes in RT, with moment-to-moment variability (Fast Frequency Area Under the Spectra, FFAUS) and slow changes in RT (Slow Frequency Area Under the Spectra, SFAUS) computed. The ex-Gaussian analysis was performed in all three studies, and the FFT analysis was performed in the SART and Flanker SART. From the EEG recording, functional connectivity between 64 electrodes was examined, and global efficiency and modularity were computed, reflecting functional integration and segregation of the brain respectively. There was a positive association between tau and levels of ADHD symptoms in all three studies, but sigma showed no significant association in any of the studies. This finding suggests that higher levels of ADHD symptoms are associated more occurrences of attentional lapses and greater RTV. FFAUS was positively associated with levels of ADHD symptoms in both the SART and Flanker SART, suggesting that individuals with higher levels of ADHD symptoms show difficulty with sustained attention. SFAUS was positively associated with levels of ADHD symptoms only in the SART. Greater task complexity presented by flankers might help to increase arousal levels for those with more pronounced levels of ADHD symptoms. Adolescents demonstrated lower RTV than the children in all RTV measures, indicating stability of performance increases from late childhood to late adolescence. The graph analysis of EEG functional connectivity showed that lower RTV was associated with more integrated brain network functioning, as measured by global efficiency. This supports the view that stable responses are achieved through more integrated brain functioning. More integrated brains may allow for more efficient transfer of information resulting in more stable responses. Adolescents showed greater levels of integration and lower levels of segregation of the brain during performance, suggesting that the brain might be becoming more integrated and less segregated from late childhood to late adolescence.
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ItemPsychological and neurobiological mechanisms underpinning chronic tinnitus( 2017)Chronic tinnitus, the phenomenon of a ringing, buzzing or hissing type sound in the ears or head is a prevalent health condition affecting 10-15% of the general population (Henry, Dennis, & Schechter, 2005a). It can have significant negative effects on an individual’s health and wellbeing and is associated with significant economic burden (Maes, Cima, Vlaeyen, Anteunis, & Joore, 2013; Tyler & Baker, 1983). At present, there is no cure for chronic tinnitus, likely due to the lack of consensus regarding the mechanisms maintaining the presence or impact of chronic tinnitus on individuals experiencing this condition. This thesis aimed to determine if psychological factors, and associated neural networks, could be maintaining awareness of the tinnitus sound and the severity of its impact. To achieve this objective, four studies were conducted utilising meta-analytic, questionnaire, cognitive and neuroimaging techniques. The first study comprehensively and systematically reviewed current literature regarding the psychological functioning of adults with chronic tinnitus. Results suggest that a heterogeneous array of psychological functions may be involved in the experience of chronic tinnitus, particularly emotional and cognitive functions, with meta-analyses providing consistent evidence for a role of reduced emotional wellbeing in both the presence and impact of chronic tinnitus. Study 2 and 3 further investigated the role of emotional and cognitive factors respectively in chronic tinnitus. Specifically, Study 2 investigated possible interactions between psychological factors and the vicious cycle of hypervigilance to the tinnitus sound in a heterogeneous community sample of 81 adults with chronic tinnitus. While analyses replicated the presence of the vicious cycle, this was conditional on the experience of depressive symptoms. Study 3 aimed to determine the contribution of cognitive functioning to chronic tinnitus. Compared to healthy-hearing individuals (n=26) people with chronic tinnitus (n=26) showed significant impairments in cognitive control, inhibitory control and increased symptoms of depression, with depressive symptoms and cognitive control successfully discriminating between people with and without chronic tinnitus. Combined, these studies suggest that disruption of specific large-scale neurocognitive networks proposed to underpin a range of psychological and cognitive symptoms; particularly those associated with depression may also underpin chronic tinnitus. As such, the final study of this thesis investigated the functioning of our stable neurocognitive networks, specifically the cognitive control network, in people with chronic tinnitus (n=15) and matched controls (n=15). While both groups successfully engaged the cognitive control network, the chronic tinnitus group exhibited subtle disruptions to a core node of this network, namely the right middle frontal gyrus, revealing both attenuated activation during cognitive engagement. This region also showed decreased connectivity with a node of the salience network, the right anterior insula, and increased connectivity with nodes of the autobiographical memory network, namely left posterior cingulate cortex and left medial prefrontal cortex. Together, the results of this thesis identify a failure in the process of attention-switching and the associated neurocognitive networks as a core mechanism underpinning the persistent awareness and pervasive impact of chronic tinnitus. This provides a novel framework, the Attention-Switching Model, for investigating both the experience of tinnitus, and potential treatments to help people with chronic tinnitus.
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ItemA longitudinal study of attention and inhibitory control in 6- to 11-year-old children( 2017)Attention and inhibitory control are important cognitive abilities. Attention consists of three components: activation, selection, and control. The activation of attention involves alertness, the maintenance of response readiness, and sustained attention. The selection of attention involves reflexive and voluntary shifts of attention to a specific location or point in time, and the breaking and reorienting of attention. The control of attention involves resolution of conflict, such as that induced by distractors, and inhibitory control. There is a lack of longitudinal data on the development of these aspects of attention in typically developing children, so their developmental trajectories remain unclear. The aim of this thesis was to map the developmental trajectories of alerting, sustained attention, orienting, reorienting, conflict resolution and inhibitory control. Participants involved in this research were 114 children aged 6, 8, or 10 years at study onset, referred to as the 6-7, 8-9, and 10-11 groups. Children performed three attention tasks, three times at 6-monthly intervals. The Attention Network Task (ANT) measures alerting, orienting, reorienting, and conflict resolution. The Random Sustained Attention to Response Task (SART) and the Fixed SART measure sustained attention and response inhibition; they require frequent responding with infrequent inhibition to a No-Go target. Intra-individual variability of response time (RT) during the SART was analysed with a Fast Fourier Transform and an ex-Gaussian model of RT data. Results indicate that each component of attention followed a different rate of development. In terms of activation, there was ongoing maturation throughout the study. The functioning of the alerting network, as measured by the ANT, improved over the year in all children. There was, however, little difference in alerting score between the two youngest groups, suggesting greater maturation of alerting after 9 years of age than before. Findings for sustained attention were task-dependent: during the arousing Random SART, there were few differences in performance between the two older groups, but during the unengaging Fixed SART, the 8-9 group mostly performed at an intermediate level compared with the other groups. The 8-9 group exhibited greater momentary fluctuations in response time and made more very long responses than the 10-11 group on both SARTs, indicating more momentary lapses in attention. The 6-7 group performed less well than the older groups on most measures on both SARTs. The selection of attention - the orienting and reorienting networks as measured by the ANT - showed no developmental changes during the study. Control of attention - conflict resolution and response inhibition as measured by the ANT and Random SART - was relatively stable from 7 and 8 years respectively. This thesis proposes that between 6 and 7 years is an important period for the development of attention and response inhibition. There may be some level of developmental stability between 8 and 11 years on unpredictable engaging tasks. The ability to self-sustain attention and arousal on an unarousing unengaging task, however, appears to follow a protracted maturation throughout childhood.
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ItemInvestigating anxiety and depression in adults with low intellectual ability( 2016)Adults with low ability have been routinely excluded from general population research that supports cognitive behavioural therapy for anxiety and depression. Even studies using samples of adults with ability below average exclude potential participants with profound and severe intellectual disability, without testing task-specific capacity. Consequently, little is known about the viability of cognitive models of anxiety and depression amongst adults with low ability. The present study addresses this through four main lines of enquiry: inclusion of all abilities through screening and validity procedures; prevalence of signs and symptoms of anxiety and depression as well as the impact of life stressors on these; cognitions and their specificity for anxiety and depression; and the impact of anxiety and ability on attentional responses to emotional stimuli. A sample of 70 adults from each level of low ability, unselected for signs or symptoms of anxiety and depression, was recruited from community-based disability support services. Participants were screened for general (receptive language) and task-specific abilities, interviewed for symptoms of anxiety and depression and disorder related cognitions then administered a visual-probe task with emotional face stimuli. Informants provided data on signs of mental ill-health, stressful life events and adaptive behaviour. Task-specific validity procedures governed data included for analysis. The inclusionary approach meant participants from all ability levels below average were included. Task-specific screening measures were superior to receptive language in predicting validity on research tasks, especially for participants with severe and profound intellectual disability. Dimensional measurements meant ability variables could be covaried or controlled in most analyses. Mean levels of signs and symptoms were lower than those in available reference studies, as were the rates of clinical level cases. General ability was positively correlated with signs of anxiety and depression but was not related to symptoms. Similarly, the number of life events was correlated with all scales on the measure of signs but not with symptoms of anxiety or depression. The lack of concordance highlights the gap between what informants see and what respondents think and feel. Learning a person’s subjective interpretation of events can help understand their emotions and behaviour. Depressive cognitions uniquely predicted significant variance in symptoms of depression but only ability, rather than anxious cognitions, predicted anxiety symptoms. Cognitive content-specificity for depression bolsters support for the use of cognitive behaviour therapy but further research into the relationship between ability and anxiety is required. The lack of directional bias in selective attention to emotional faces in any of the anxiety or ability groups means cognitive-motivational theory was not supported but future studies should address methodological issues. Attentional control theory was supported but the slowing of emotional face processing caused by high anxiety, but not depression needs replication. Trials of attentional training may be justified to reduce anxiety. Further research into cognitive models of anxiety and depression is urgently needed and future studies should ask theoretical as well as clinical questions.
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ItemNeural correlates of attention in the context of prematurity( 2014)This study aimed to examine attention outcomes in a high-risk very preterm (VPT; <30 weeks’ gestational age) and/or very low birth weight (VLBW; <1250 g) children at 7 years, and to assess whether brain abnormality measured by neonatal magnetic resonance imaging (MRI) can predict later adverse outcome within this domain. It also aimed to investigate whether the attention difficulties observed at 7 years were associated with abnormalities in the key white matter pathways associated with attention. A cohort of 198/224 VPT/VLBW children and 70/77 term controls were examined. Neonatal MRI scans performed at term-equivalent age were assessed for white matter, cortical grey matter, deep grey matter, and cerebellar abnormalities. Standardised neuropsychological tests of attention and MRI scans were conducted at 7 years. Diffusion tractography analyses were performed on the key white matter tracts associated with attention (the superior longitudinal fasciculi, the cingulum bundles, and the reticular activating system). At 7 years of age, the VPT/VLBW group performed significantly worse than term controls on all attention outcomes. Associations between higher neonatal brain abnormality scores and adverse attention performances at 7 years were found in the VPT group; in particular, white matter and deep grey matter abnormalities were reasonable predictors of long-term attention outcomes. Findings at 7 years also revealed altered microstructural organisation and reduced tract volume within the proposed attention tracts in the VPT children compared with the term controls and also that, such alterations were related to the adverse attention outcomes in VPT children. Attention is a significant area of concern in VPT/VLBW children. This is the first study to show that neonatal brain pathology may be used to predict, in conjunction with other known risk factors, which children may be at risk of later adverse attention outcomes. This study also highlights the importance of white matter tract integrity for the development of attention abilities in VPT children.
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ItemInteraction of attention and memory: a working memory model of multiple object tracking( 2013)To accurately perceive a dynamic environment, the visual system must create mental representations of specific objects and their place in the environment, must quickly and accurately update those representations as objects move, and must be able to use those representations to direct attention to appropriate objects while ignoring those that are irrelevant. This thesis investigated these processes. Three studies were conducted, each focused on a distinct but interrelated aspect of the interaction of attention and memory processes. The first study used a training experimental design to provide evidence that representations of tracking stimuli are not constrained to a visual hemifield in the manner that deployment of attention seems to be. The second study demonstrated mutual disruption between a tracking and a visual working memory task, suggesting that tracking and visual working memory share resources of both attention and memory. The final study provided evidence to suggest that motion does not contribute to tracking when location is more informative. These results are synthesised with previous models of multiple object tracking, and with a multicomponent model of working memory, to develop a model that is able to account for each of the findings of this thesis.