In the first years of life there is a dramatic development of cognitive abilities supporting cognitive control of behavior. This development allows the child to make future-oriented predictions and to increasingly act in a goal-directed manner. The early development of cognitive control is presumably closely tied to the maturation of the attention systems. Further, attentional control processes have been suggested to be the unifying construct underlying cognitive control in both children and adults. The general aim of the present thesis was to further our understanding of the early development of cognitive control. This aim was approached by examining the attention processes underlying cognitive control in infancy and toddlerhood, with a particular focus on age-related improvements in attentional control. This thesis consists of three studies that have used the A-not-B paradigm to investigated infants’ and toddlers’ ability to search for a hidden object or to correctly anticipate the reappearance of a hidden object. The A-not-B paradigm is one of few well-studied paradigms for research on the early development of cognitive control and this paradigm involves conflict resolution and requires a flexible shift of response set to achieve a goal. Study I of this thesis examined individual differences in 10-month-olds’ ability to search for a hidden object in a manual A-not-B task. We investigated the infants’ search behavior, both in terms looking and reaching responses, the relation between individual differences in performance on A and B trials, and also the relation between the two response modalities. Study II used eye tracking and focused on the role of attentional demand on 10- and 12-month-olds’ ability to anticipate the reappearance of a hidden object. This study intended to clarify age-related improvements, particularly in relation to the ability to resist visually distracting information that interfered with the task at hand. Study III also employed an eye tracker to measure 18-month-olds’ predictive eye movements in anticipation of a hidden object under conditions marked by different attention demands. This study not only investigated the toddlers’ ability to overcome a visual distractor, but also their ability to keep a representation in actively in mind over different delays. In addition, the 18-month-olds’ performance was compared to that of an adult group to shed further light on the development of attentional control in children. In conclusion, this thesis demonstrated that important age-related improvements in cognitive control take place by the end of the first year of life and between 12 and 18 months of age. More specifically, with increasing age, the children were able to resolve higher levels of conflict thereby demonstrating improvements in attentional control. In interpreting the present data, we argue that this development is gradual, developing from variable to stable and also that the attentional control process is best described as continuous rather dichotomous in infancy and toddlerhood. Based on our findings, future research should be motivated to examine changes in attentional control processes in relation to the early development of cognitive development.

The majority of memory research, and research on its cognitive underpinnings has thus far focused on retrospective memory, or memory for things learned or rehearsed in the past. More recently, however, prospective memory, or the memory for future intentions, has become a major area of research. It is theorized that prospective and retrospective memory may both rely on similar constituent parts such as working memory and selective attention; the relationship between these constructs and prospective memory is, however, significantly less clear than for retrospective memory. In this study we sought to further clarify the role that cognitive process play in prospective memory performance using an SEM approach that included monitoring as a mediating variable in addition to focal, non-focal, and time-based prospective memory task condition. Results suggest a monitoring component is important in both focal and non-focal conditions, and that the type of monitoring observed in this study is related primarily to proactive interference, and reflects participants’ ability to disengage from no longer relevant stimuli¬¬¬.

The unique linguistic experience of bilingualism purportedly produces cognitive control advantages. Although there is a significant body of evidence supporting this view, there are also several recently published research studies that failed to replicate bilingual advantages. Furthermore, there is some evidence of a publication bias that favors findings supporting a bilingual advantage. The purpose of this study was to address this discrepancy in the literature by examining performance of bilinguals and monolinguals on a variety of cognitive control tasks. A second purpose was to determine how bilinguals are able to achieve better performance if they do indeed have an advantage. Specifically, we were interested in whether there were differences in the tendency for bilinguals and monolinguals to mind wander, a phenomenon associated with poorer cognitive control performance. We hypothesized that bilinguals would demonstrate better performance than monolinguals on Operation Span, Numerical Stroop, SART, Color- Shape, and Letter Memory tasks, which are measures of working memory, proactive inhibition, reactive inhibition, shifting, and updating, respectively. We further hypothesized that if bilinguals outperformed monolinguals on these tasks, this would be associated with less mind wandering for bilinguals. Participants completed all measures of cognitive control and were probed periodically throughout the tasks for mind wandering. Accuracy and reaction times where appropriate were recorded for each task, and data from 52 monolinguals and 52 bilinguals were analyzed. The results did not reveal any bilingual advantages. For all tasks, performance of the two groups was equivalent with the exception that monolinguals had faster reaction times for Numerical Stroop, SART, and Color-Shape tasks. There were also no differences between language groups in mind wandering tendencies. Secondary analyses examining age of acquisition (i.e., early versus late) and similarity of languages (i.e., same-script versus differentscript) did not change the overall pattern of no bilingual advantages. The lack of a bilingual advantage supports recent calls to temper bilingual advantage claims and shows a need for future research to address which underlying factors of bilingualism may or may not have an effect on cognitive control.

The topic of this thesis is cognitive control: how the brain organises itself to perform the many tasks it is capable of and how it switches flexibly among them. Task-switching experiments reveal a substantial cost in reaction time and accuracy after a switch in tasks. This "switch cost" is reduced by preparation (suggesting anticipatory task-set reconfiguration), but not eliminated. The thesis focuses on the sources of the "residual" cost. Most accounts attribute it to response selection being prolonged on a task-switch trial by task conflict, e.g. by 'task-set inertia' — persisting activation/inhibition of the previous task's S-R rules — or their associative reactivation by the stimulus. Four experiments used event-related potentials (ERPs) to determine which stages of task processing are influenced by a change in tasks, looking for delays in process-specific markers in the ERP. Experiments 1 and 2 showed that a prepared switch to a reading task from a perceptual judgement delayed early ERP markers of lexical access by a large fraction of the RT switch cost, suggesting that a substantial part of the residual cost arises in processes earlier than response selection, possibly due to task-related attentional inertia. Markers of lexical access observed in the non-lexical task were larger on switch than repeat trials, providing the first electrophysiological evidence of task-set inertia. Experiment 3 examined the effects of an unprepared switch in the same way. ERP waveforms were modulated by a switch before markers of lexical access were evident, suggesting additional processing demands compete for resources with lexical access. A simple delay, however, was not found; post-stimulus task-set reconfiguration does not just insert an extra processing stage. Experiment 4 looked for a delay in the onset of an early ERP marker of emotional processing when the task switched between categorising facial expression and classifying a superimposed letter. No such delay was found in this case, and ERP markers of emotion processing were present to the same extent in the letter task. This suggests that, given appropriate spatial attention, processing facial emotion unfolds automatically, independent of attention allocation to the facial features. Experiments 5-7 further explored the link between conflict due to processing the irrelevant stimulus dimension and the ERP post-stimulus negativity that accompanies the residual cost. The negativity could be elicited even on trials of non-switching blocks by prior training on classifying the irrelevant attribute of the stimulus using the same responses. But this effect did not seem to result from the trained class of irrelevant attribute attracting more attention. Finally, Experiment 8 followed up an incidental observation in Experiment 1 to establish the novel observation that a task-switching context abolishes the usual ERP correlate of withholding a response in a go/no-go paradigm, suggesting an interesting interaction between task-set control and response inhibition.

Task switching produces a number of reliable behavioural measures, the main focus of interest here being 'switch cost', the increase in response time when switching between tasks as opposed to performing them separately. Switch costs are typically measured between two tasks and compared to a single-task repeat condition. Current explanations of switch cost fall broadly into either active reconfiguration based accounts (e.g. Rogers & Monsell, 1995) whereby the extra time taken to switch between tasks is attributable to reconfiguration of task set, or passive carryover accounts (Allport, Styles & Hsieh, 1994) where extra time is accrued by the need to overcome conflict between the current task set and the enduring activity of the previous task set. This thesis used the Continuous Series II (Gurd, 1995), a novel continuous verbal switching task which requires individuals to switch continuously between increasing numbers of overlearned sequences (e.g. days, numbers). The aim was to investigate the application of general (whole-task) switch costs (RT costs), memory-based switching and the differential pattern of errors produced by the task, with a view to determining the most appropriate theoretical model to explain costs in the task. General switch costs are measured over the whole time course of the task from beginning to end, instead of the more usual measurement of switch cost over a single switch or repeat within the whole task. Such long-term measures of switch cost account for 'global representational structures' in the task, which are said to contribute to the cost of switching yet are absent from local transitional measures (Kleinsorge, Heuer & Schmidtke, 2004). Global representational structures account for not only the current and preceding trials actually performed but also the possible alternatives for the preceding, current and subsequent trials, thereby reflecting all representations relating to performance of the tasks. The Continuous Series II (Gurd, 1995) measures costs continuously over time between increasing numbers of verbal tasks and as yet has not been linked to either a reconfiguration or carryover-based account. Initial administration to healthy controls and neurological patients confirmed difficulty-related increasing costs and revealed a dissociation of errors between two versions of the task, one including semantic categories. This suggested differential sources of control overseeing conflict detection and resolution, linked in this work to Kahneman's dual system model (Kahneman, 2011) and suggesting the implication of active control. Further work with monozygotic twins mirrored for handedness revealed no predicted effect of handedness but did reveal the employment of vocalised inner-speech as a successful self cueing device, known to be supportive of active reconfiguration in switching (Monsell, 2005). Such cueing was employed by this sample of older adults but had not appeared to benefit the neurological patients who clearly had reconfiguration deficits. Further development of the two versions of the task also allowed rejection of a passive carryover explanation of switch-cost on the basis that switching to the easier task was not more difficult, counter to the prediction of Allport, Styles & Hsieh (1994). At this stage it was evident that some portion of general cost for the task may be artefactual, as participants displayed behaviour suggesting the order of tasks and their updating nature (task content) may be inflating cost beyond a pure measure of switching (an inevitable risk of general switch cost measurement). Investigation of task order showed that production of the category 'days' appeared to conflate sources of error. Reducing the difficultly of component tasks (removing the need to update items) demonstrated that a substantial proportion of general cost was indeed purely switch-related. Returning to the question of cueing (previously demonstrated to be beneficial when self-generated), the final study introduced explicit external cues, consistently predicted to benefit switching (Monsell, 2005). These cues did not reduce time costs in verbal task switching and furthermore failed to prevent errors of task order. The lack of external cue benefit supports an amended version of the Rogers & Monsell (1995) task-set reconfiguration model as the best explanation of switch costs in verbal task-switching. This amended model relies entirely on internally generated representations in a closed system and supports the role of active control in generating switch-cost. General cost, while incorporating task-related artefacts, rehearsals and error recovery, nevertheless has at its core a switch related element. Furthermore, the failure of cues to extinguish between-task errors negates excessive reliance on working memory and further supports the rejection of passive carryover accounts of task switch cost.

Objectives: Due to a number of conceptual and methodological limitations, existing research has provided only equivocal evidence that deficits/biases in attentional control (AC) are causally implicated in depressive rumination and/or that Cognitive Control Training (CCT) can be used to remediate such vulnerabilities. By using a well-validated training task and ensuring adequate training exposure, the current study aimed to examine the hypothesis that daily CCT would reduce rumination and improve mood among participants with elevated ruminative disposition. Method: Using a multiple baseline design (MBD), eight high-ruminating university participants rated their daily levels of rumination and mood before and after the randomly-determined introduction of daily CCT, designed to enhance their level of AC. Daily ratings were compared before and after the introduction of CCT, using systematic visual analysis and randomisation tests for significance at the group level. Results: No evidence was found to support the hypothesis that daily CCT reduces rumination and/or improve mood. While participants improved in their performance within the CCT across the training period, there was no evidence of near- or far-transfer, visual analysis revealed no impact of the introduction of daily training, and all group-level analyses were non-significant (p ≥ .05). Conclusion: Despite addressing a number of conceptual/methodological concerns, the current study provides no further support for AC theories of rumination or the use of CCT-based treatments for depression. Such conclusions must be interpreted in light of other methodological limitations, however, including the use of a non-clinical sample and the use of MBD to detect delayed treatment effects.

Two aspects of cognitive control were investigated using the item-recognition task and the verb generation task. The item-recognition task had two conditions, high and low interference. The verb generation task was manipulated in three ways, for different levels of interference and time interval. The intention was to more deeply investigate one aspect of the item-recognition task, comparing response times for different trial types in different conditions, and to investigate a fatigue effect between the item-recognition and verb generation task. Thirty-two participants were tested at two occasions, in a within-subjects design. Results for the verb generation task revealed effects for levels of interference and time interval, although there was no difference in the manipulation. Results for the item-recognition task revealed effects for condition and trial type, as well as an interaction effect between these. The non-familiar trials in the high interference condition resulted in faster response times compared to the same kind of trials in the low condition. The result from the item-recognition task extends those from previous studies, revealing details for differences between trial types. This finding demonstrates a carry-over facilitation effect.

<p>Two aspects of cognitive control were investigated using the item-recognition task and the verb generation task. The item-recognition task had two conditions, high and low interference. The verb generation task was manipulated in three ways, for different levels of interference and time interval. The intention was to more deeply investigate one aspect of the item-recognition task, comparing response times for different trial types in different conditions, and to investigate a fatigue effect between the item-recognition and verb generation task. Thirty-two participants were tested at two occasions, in a within-subjects design. Results for the verb generation task revealed effects for levels of interference and time interval, although there was no difference in the manipulation. Results for the item-recognition task revealed effects for condition and trial type, as well as an interaction effect between these. The non-familiar trials in the high interference condition resulted in faster response times compared to the same kind of trials in the low condition. The result from the item-recognition task extends those from previous studies, revealing details for differences between trial types. This finding demonstrates a carry-over facilitation effect.</p>

The present study investigated age differences in implicit memory for positive, negative and neutral words. We also explored how cognitive control and time of testing influence emotional memory. Participants completed a one-back picture comparison task with superimposed distracting emotional and neutral words. Memory for distracting words was tested using an implicit memory test and cognitive control by a flanker task. Priming was significant for negative but not for positive and neutral words. Memory for distracting negative words was greater at non-optimal times of day for young adults but similar across the day for older adults. A high level of cognitive control was related to greater priming for negative words in young adults and lower priming in older adults. Priming for neutral words was enhanced in high cognitive control participants when stimuli contained emotional words that were relevant to one’s goals, implicating the use of emotion regulation at an unconscious level.

The present study investigated age differences in implicit memory for positive, negative and neutral words. We also explored how cognitive control and time of testing influence emotional memory. Participants completed a one-back picture comparison task with superimposed distracting emotional and neutral words. Memory for distracting words was tested using an implicit memory test and cognitive control by a flanker task. Priming was significant for negative but not for positive and neutral words. Memory for distracting negative words was greater at non-optimal times of day for young adults but similar across the day for older adults. A high level of cognitive control was related to greater priming for negative words in young adults and lower priming in older adults. Priming for neutral words was enhanced in high cognitive control participants when stimuli contained emotional words that were relevant to one’s goals, implicating the use of emotion regulation at an unconscious level.