The release from proactive interference (PI) is a well-studied phenomenon, but its cause is elusive. When a release in PI is caused by changes in the content of to-be-remembered items, the more accurate retrieval is likely a result of changes in context (Watkins & Watkins, 1975). However, changes in context do not readily explain the cause of PI release resulting from a temporal delay. Instead, it could be that during the delay subjects disengage from intrusive information from previous trials. The ability to disengage from no-longer-relevant information is related to fluid intelligence (Gf). I predicted that this ability to disengage, as defined by fluid intelligence, is the driving factor of the time-based release from PI. In order to test this prediction, I administered a free recall task to individuals of high and low Gf. The time between the last two lists was lengthened to cause release. The time manipulation did not cause a release from PI; essentially, this result represents a failure to replicate. Limitations of the study and potential methodological issues are discussed.

Executive control allows us to ignore distraction and switch between tasks in a flexible, yet organized fashion. While a hallmark of controlled behavior, distinctions among executive control processes are not thoroughly agreed upon. The present work explored the organization of two of these executive control processes, inhibition and shifting, and their relationship to each other. There were two primary goals. The first goal was to investigate the distinction among inhibitory control processes, as “inhibition” has oftentimes been considered a unitary construct. For example, there is evidence that response-distractor inhibition, which involves resolving interference from dominant responses or distractors in the external environment, is different from resistance to proactive interference (PI), which involves overcoming interference from previously relevant representations in memory. Using aging, neuropsychology, and individual differences methodologies, I investigated the unity and diversity of inhibitory control mechanisms. The healthy aging and neuropsychological evidence supported a distinction between response-distractor inhibition and resistance to proactive interference. However, when controlling for processing speed, the individual differences work suggested a need for further specification, as only a subset of these tasks emerged in the single factor model that provided the best fit to the data. The second goal was to explore how inhibitory control processes interact with task switching, as some theoretical accounts of task switching have suggested that switch costs result from the need to overcome interference from the previously relevant task. Inconsistent with these theories, I found little relation between inhibitory control and measures of global and local task switching, and instead, working memory served as the best predictor of these shifting measures. In contrast, inhibitory control was related to the backward inhibition abilities of older adults. These findings are discussed within a theory of working memory that accounts for the patterns of results found across the different methodologies.

Executive control allows us to ignore distraction and switch between tasks in a flexible, yet organized fashion. While a hallmark of controlled behavior, distinctions among executive control processes are not thoroughly agreed upon. The present work explored the organization of two of these executive control processes, inhibition and shifting, and their relationship to each other. There were two primary goals. The first goal was to investigate the distinction among inhibitory control processes, as “inhibition” has oftentimes been considered a unitary construct. For example, there is evidence that response-distractor inhibition, which involves resolving interference from dominant responses or distractors in the external environment, is different from resistance to proactive interference (PI), which involves overcoming interference from previously relevant representations in memory. Using aging, neuropsychology, and individual differences methodologies, I investigated the unity and diversity of inhibitory control mechanisms. The healthy aging and neuropsychological evidence supported a distinction between response-distractor inhibition and resistance to proactive interference. However, when controlling for processing speed, the individual differences work suggested a need for further specification, as only a subset of these tasks emerged in the single factor model that provided the best fit to the data. The second goal was to explore how inhibitory control processes interact with task switching, as some theoretical accounts of task switching have suggested that switch costs result from the need to overcome interference from the previously relevant task. Inconsistent with these theories, I found little relation between inhibitory control and measures of global and local task switching, and instead, working memory served as the best predictor of these shifting measures. In contrast, inhibitory control was related to the backward inhibition abilities of older adults. These findings are discussed within a theory of working memory that accounts for the patterns of results found across the different methodologies.

In recent years, students and educators alike have utilized new technologies such as tablet computers as a means of enhancing the learning process. While prior research suggests that these implementations within the classroom provide a new and beneficial method of relaying and learning information, scientists have begun to explore the possible side effects that these technologies have on the learning process. Although much of the current literature suggests that learning from an electronic screen does not affect efficacy compared to learning from printed text (Bayliss et al., 2012; Dundar & Akcayir, 2012), researchers continue to explore the possible consequences that using said technologies may have in academia. The current study aims to address how tablet computers affect the process of learning differently across levels of education. It is proposed that older generations, such as college students, who did not grow up with tablets in the classroom may suffer from the effects of proactive interference when compared to younger students who have been exposed to technologies much more profoundly in their education (e.g. elementary students). If this is so, the current study also proposes a possible intervention that would help students at any educational level overcome this interference in order to integrate tablets into their studies effectively.

Detecting and interpreting sensory events, and remembering those events in in the service of future actions, forms the foundation of all behavior. Each of these pillars of the so-called "perception-action cycle" have been topics of extensive inquiry throughout recorded history, with philosophical foundations provided by early BCE and CE periods (especially during the Classic and Renaissance eras) leading to intensive empirical study in the twentieth and twenty-first centuries. Such experiments have described detailed (but incomplete) behavioral functions reflecting perception and memory, and have begun to unravel the extraordinarily complex substrates of these functions in the nervous system. The current dissertation was motivated by these findings, with the goal of meaningfully extending our understanding of such processes through a multi-experiment approach spanning the behavioral and neurophysiological levels. The focus of these experiments is on short-term memory (STM), though as we shall see, STM is ultimately inseparable from sensory perception and is directly or indirectly associated with guidance of motor responses. It thus provides a nexus between the sensory inputs and motor outputs that describe interactions between the organism and environment. In Chapter 2, previous findings from nonhuman primate literature describing relatively poor performance for auditory compared to visual or tactile STM inspired similar comparisons among modalities in humans. In both STM and recognition memory paradigms, accuracy is shown to be lowest for the auditory modality, suggesting commonalities among primate species. Chapters 3-5 examined STM processing in nonhuman primates at the behavioral and neurophysiological levels. In Chapter 3, a systematic investigation of memory errors produced by recycling memoranda across trials (proactive interference) is provided for the understudied auditory modality in monkeys. Such errors were ameliorated (but not completely eliminated) by increasing the proportions of unique memoranda presented within a session, and by separating successive trials by greater time intervals. In Chapter 4, previous results revealing a human memory advantage for audiovisual events (compared to unimodal auditory or visual events) inspired a similar comparison in monkeys using a concurrent auditory, visual, and audiovisual STM task. Here, the primary results conformed to a priori expectations, with superior performance observed on audiovisual trials compared to either unimodal trial type. Surprisingly, two of three subjects exhibited superior unimodal performance on auditory trials. This result contrasts with previous results in nonhuman primates, but can be interpreted in light of these subjects' extensive prior experience with unimodal auditory STM tasks. In Chapter 5, the same subjects performed the concurrent audiovisual STM task while activity of single cells and local cell populations was recorded within prefrontal cortex (PFC), a region known to exhibit multisensory integrative and memory functions. The results indicate that both of these functions converge within PFC, down to the level of individual cells, as evidenced by audiovisual integrative responses within mnemonic processes such as delay-related changes in activity and detection of repeated versus different sensory cues. Further, a disproportionate number of the recorded units exhibited such mnemonic processes on audiovisual trials, a finding that corresponds to the superior behavioral performance on these trials. Taken together, these findings reinforce the important role of PFC in STM and multisensory integration. They further strengthen the evidence that "memory" is not a unitary phenomenon, but can be seen as the outcome of processing within and among multiple subsystems, with substantial areas of overlap and separation across modalities. Finally, cross-species comparisons reveal substantial similarities in memory processing between humans and nonhuman primates, suggesting shared evolutionary heritage of systems underlying the perception-action cycle.

Working memory (WM) capacity – the capacity to maintain and manipulate information in mind – plays an essential role in high-level cognitive functions. An important determinant of WM capacity is the ability to resolve interference of previously encoded but no longer relevant information (proactive interference: PI). Four different mechanisms of PI resolution involving binding and inhibition have been proposed in the literature, although debate continues regarding their role. Braver et al. (2007) introduced an important distinction in the PI resolution literature, proposing two general types of PI control mechanisms that occur at different time points: proactive control (involves preparation in advance of the interference) and reactive control (occurs after interference occurs). This thesis proposed that among these four functions involving binding and inhibition, item inhibition and binding could be involved in proactive control, while familiarity inhibition and episodic inhibition could be involved in reactive control. The question is which mechanism in each pair is indeed involved in proactive control and reactive control respectively, and how these proactive control and reactive control mechanisms work together to resolve PI. In addition, do these mechanisms play a role in the relationship between PI resolution and WM? In an individual differences study, individuals’ ability to resolve PI was assessed in memory tasks, with two versions of each that encouraged the use of either proactive or reactive control. In addition, measures were obtained of individuals’ ability of binding and inhibition in tasks that had minimal memory demands. Regression analyses showed contributions of binding and inhibition to PI resolution and WM. Moreover, these functions are responsible for the correlation between PI resolution and WM. In a neuroimaging study, the neural basis of proactive control was examined by comparing two memory tasks that differed in their demand on binding and inhibition. In addition, the brain regions engaged in reactive control was examined by contrasting trials involving interference or not. The thesis showed that item inhibition carried out by the left inferior frontal cortex (IFC) is involved in proactive control while episodic inhibition carried out by the left IFC and the posterior parietal cortex is involved in reactive control.

The limited capacity of working memory forces people to update its contents continuously. Two aspects of the updating process were investigated in the present experimental series. The first series concerned the question if it is possible to update several representations in parallel. Similar results were obtained for the updating of object features as well as for the updating of whole objects, participants were able to update representations in parallel. The second experimental series addressed the question if working memory representations which were replaced in an updating disappear directly or interfere with the new representations. Evidence for the existence of old representations was found under working memory conditions and under conditions exceeding working memory capacity. These results contradict the hypothesis that working memory contents are protected from proactive interference of long-term memory contents. / Aufgrund der begrenzten Kapazität des Arbeitsgedächtnisses müssen seine Inhalte ständig aktualisiert werden. Zwei Aspekte des Aktualisierungsprozesses wurden in Experimentalserien untersucht. Die erste Serie betraf die Frage, ob es möglich ist, mehrere Repräsentationen gleichzeitig zu aktualisieren. Ähnliche Ergebnisse ergaben sich sowohl für das Aktualisieren von Objektmerkmalen als auch für das Aktualisieren von ganzen Objekten, die Versuchsteilnehmer konnten Repräsentationen gleichzeitig aktualisieren. In der zweiten Experimentalserie wurde die Frage untersucht, ob Arbeitsgedächtnisrepräsentationen, die bei einer Aktualisierung ersetzt worden sind, sofort verschwinden oder mit den neuen Repräsentationen interferieren. Evidenz für das Vorhandensein alter Repräsentationen wurde unter Arbeitsgedächtnisbedingungen und unter Bedingungen, bei denen die Arbeitsgedächtniskapazität überschritten wird, gefunden. Diese Ergebnisse widersprechen der Hypothese, dass Arbeitsgedächtnisinhalte vor proaktiver Interferenz aus dem Langzeitgedächtnis geschützt sind.

Doctor of Philosophy(PhD) / The main aim of this thesis was to examine whether learning processes occur in fluid intelligence (Gf) tasks, whether it is essential for them to occur for induction to take place and whether they contribute to individual differences in performance. In mainstream differential research, Gf is conceptualised as a factor important in induction tasks that are considered novel and context-free (Cattell, 1963, 1987). Thus, performance has typically been assumed to be uninfluenced by previous acquisitions of knowledge structures. Sources of individual differences in Gf task performance have been attributed to working memory capacity (WMC), particularly individual differences in the ability to combat proactive interference. In contrast, the cognitive reasoning literature associates induction with the use of prior conceptual knowledge. A middle-ground position is that Gf tasks may require learning to occur across the task, which would draw upon WMC. That is, individual differences in Gf task performance may be due to knowledge learnt across the task, rather than knowledge brought to the task. Gf items have traditionally been presented in easy-to-hard order but easier items may unintentionally provide learning opportunity for harder items. This would contradict both classic and modern test theories which make the assumption that items within a task are independent of each other. The learning hypothesis was explored in the current work along with the issue of whether it is possible to reliably solve complex Gf items without some relevant, prior knowledge. Also, the distinction between within-item induction and across-item learning was investigated, along with the relationship between across-item learning and proactive interference. An experimental-differential approach was used to manipulate learning opportunity within Gf tasks in four experiments. The first experiment examined whether learning takes place in Raven’s Advanced Progressive Matrices (Raven, 1962) and if so, to what extent this learning is a source of individual differences. Specifically, whether rule learning within the task is necessary for abstraction to take place and whether those of higher Gf ability learn faster than those of lower Gf ability. The next three experiments examined the distinction between knowledge that may be brought to the task, learning that occurs across multiple items in the task and induction within a single item that may be independent of any prior knowledge including knowledge learnt across the task. The effect of proactive interference as a consequence of learning and knowledge was also investigated. The experiments examined which of these are relevant to general performance (i.e., common to everyone) and which contribute to individual differences. Learning-opportunity was manipulated in a task from the cognitive reasoning literature – the Modified Sweller and Gee (MSG) Task. Traditional Series Completion tasks were used as Gf markers and data analyses employed Hierarchical Linear Modelling (HLM). The advantage of the MSG Task is that it has qualities typical of Gf tasks but unlike conventional Gf tasks, it is able to assess within-item induction in isolation from any potential influences from across-item learning. This is because it involves multiple attempts within each item with feedback, allowing single items to be administered reliably. When across-item learning opportunity is absent, the MSG Task is able to provide an estimate of participants’ within-item induction success through the number of attempts they need within a single item. The amount participants learn across items can be approximated by comparing performance on items preceded by learning opportunity (i.e., easier items with similar rule-types), with items not preceded by learning opportunity. Lastly, the effects of proactive interference can be evaluated by comparing performance on items preceded by interference (i.e., items with different rule-types) with those that are not preceded by interference. Overall, it was found that with no learning opportunity leading up to novel items (to provide relevant prior knowledge), solution was nearly impossible for all participants. When learning opportunity was provided, all participants were able to greatly improve their performance but those of higher Gf improved more. It was concluded that while Gf tasks appear visually novel, they must contain a combination of familiar elements in earlier items (which make use of knowledge that participants bring to the task) and novel elements in later items (which require the use of knowledge that must be learnt from earlier items); and those of higher Gf perform better on Gf tasks, at least partly because they are able to benefit more from the learning opportunity provided by earlier items. It was found that proactive interference affects all participants when they learn from prior items. However, insufficient evidence was found to suggest that the ability to combat proactive interference contributes to individual differences in performance.

One hypothesis regarding the etiology of Attention-Deficit/Hyperactivity Disorder (ADHD), is to conceptualize the disorder as an "inhibition" disorder. Furthermore, it has been suggested that inhibition is not a single all-encompassing construct, but rather a series of closely related processes. There has been limited examination as to whether children with ADHD are impaired on measures of cognitive inhibition (also known as proactive and retroactive interference). This project examined children with ADHD's susceptibility to proactive and retroactive interference in both verbal and visual-spatial modalities in comparison to typically developing children utilizing a novel coding system of the Children's Memory Scale (CMS). It was found that children with ADHD exhibited greater levels of visual-spatial retroactive interference than their typically developing peers. Additionally, children with ADHD did not differ from controls on any measure of verbal interference. Implications for clinical practice and future directions for research are discussed.

Proaktiv interferens (PI) uppstår när äldre, irrelevant minnesinformation stör nyinlärning ellerframplockning av relevant information. PI påverkas av faktorer som familjaritet ochinkodning av kontextuell information. Tidigare forskning indikerar att PI har en koppling tillminnets åldrande och negativa tankeprocesser, såsom oro och ruminering. Studien undersökteom ett anpassat arbetsminnestest (2-back) kan inducera PI och om irrelevant information medolika grader av familjaritet ger olika grad av PI. Studien syftade också till att undersöka omäldre upplever mer PI än yngre samt om PI går att koppla till grad av oro och ruminering. 15yngre vuxna (20-30 år) och 10 äldre vuxna (65-69 år) genomförde ett datoriserat 2-back-testoch fyllde i skattningsformulär (PSWQ och RRS-BR). Resultatet visade att PI inducerades avtestet och att PI minskade när familjariteten minskade. Resultatet visade också att äldreupplevde en signifikant högre grad av PI på ett mått, men inte på ett annat. Ingen signifikantkoppling mellan PI och oro eller ruminering hittades. Resultaten bör dock tolkas medförsiktighet. / Proactive interference (PI) occurs when older and irrelevant memory information interfereswith new learning or retrieval of relevant information. PI is influenced by factors such asfamiliarity and the encoding of contextual information. Previous research indicates that PI hasa link to age-related memory decline and negative thought processes such as worry andrumination. The study investigated whether a modified working memory test (2-back) caninduce PI and if irrelevant information with different degrees of familiarity induces differentdegrees of PI. The study also aimed to investigate whether older adults experience more PIthan younger adults and whether PI can be linked to the degree of worry and rumination. 15younger adults (20-30 years) and 10 older adults (65-69 years) performed a computerized 2-back test and completed self-report questionnaires (PSWQ and RRS-BR). The result showedthat PI was induced by the test and that PI decreased as familiarity decreased. The results alsoshowed that the older adults experienced a significantly higher degree of PI in one measure,but not in another. No significant association between PI and worry or rumination was found.The results should be interpreted with caution.