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Research on all tested vertebrates indicates that geometric information plays a special role when organisms reorient in their environment. Some researchers have argued that geometric information is processed automatically, while landmark information is processed more slowly. These conclusions of the course of reorientation processing have been drawn from research that tested organisms accuracy in locating targets in experimental environments. However, inferences of the course of processing are not logical extensions of physical reorientation paradigms. To this end, the present research employs the psychological refractory period paradigm to investigate, over two experiments, the precise stages of processing that humans utilize when encoding an environment. The data confirm previous research by demonstrating an underadditive effect of response time across stimulus onset asynchrony (SOA) for geometric trials and an additive effect for landmark trials, suggesting that geometric information is processed during the first stage of processing, and landmark information during the second.

This thesis aims to explore the role of executive functions in multitasking. Research has shown that severe performance decrements often arise in dual-task performance, also called multitasking, as compared to single task performance. This reflects a limitation in processing temporally overlapping information. Interference between tasks arises due to a bottleneck process limited to processing only one task at a time. It has been proposed that this interference is resolved by executive functions. However, the dual-task paradigm employed in this thesis, Psychological Refractory Period (PRP) paradigm, (Pashler, 1994) is typically investigated in the field of human action performance, and the exact concept of executive functions remains underspecified. However, while underspecified in the area of action performance, executive functions have been investigated in detail in the field of memory research, more specifically in the context of working memory (WM). Therefore, the aim of this thesis was to investigate whether the executive functions in PRP are related to the executive functions as discussed in the context of WM. To test this question, we combined the PRP paradigm with a WM task, creating a complex WM span task. If the executive functions of WM and PRP are indeed related, then an interaction between the two tasks should be evident. Participants were presented with a sequence of letters to remember, followed by a processing block in which they had to perform either a single task or a dual-task, and finally were asked to recall the letters. Results (Chapter 2) showed that recall performance decreased when performing a dual-task as compared to performing a single task. This supports the assumption that PRP dual-tasks demand executive functions of WM. Following this, two other experiments were performed each with a different parametric modulation of the processing demands of the PRP dual task; response order (fixed vs random; Chapter 3) and stimulus onset asynchrony (SOA, short vs long; Chapter 4) of the component tasks. Recall performance was lower after a more difficult dual-task compared to an easier dual-task, which again indicates that demands on executive functions are increased in the dual-task. While previous neuroscientific research indeed showed that dual-tasks as well as WM tasks rely on lateral-prefrontal cortices (LPFC), it remains unknown whether both tasks activate the same areas or different sub-areas of the LPFC. Therefore, this study (Chapter 6) investigated how the neuroanatomical correlates of both dual-task and WM compare to each other. The brain activation for the PRP and WM tasks showed considerable overlap as well as some differentiation. Both tasks activated, among other areas, the inferior frontal junction. With respect to differences, the PRP task activated more the inferior middle frontal gyrus (MFG) whilst the WM component activated more the superior MFG. Thus, results support the assumption that PRP dual-tasks demand the executive functions of WM. This will allow us to inform theoretical models of cognition and to get a better understanding of human cognition. Future studies can build on this in order to create a more consolidated conceptualisation of the relationship between WM and multitasking.

abstract: Magicians are informal cognitive scientists who regularly test their hypotheses in the real world. As such, they can provide scientists with novel hypotheses for formal psychological research as well as a real-world context in which to study them. One domain where magic can directly inform science is the deployment of attention in time and across modalities. Both magicians and scientists have an incomplete understanding of how attention operates in time, rather than in space. However, magicians have highlighted a set of variables that can create moments of visual attentional suppression, which they call "off-beats," and these variables can speak to modern models of temporal attention. The current research examines two of these variables under conditions ranging from artificial laboratory tasks to the (almost) natural viewing of magic tricks. Across three experiments, I show that the detection of subtle dot probes in a noisy visual display and pieces of sleight of hand in magic tricks can be influenced by the seemingly irrelevant rhythmic qualities of auditory stimuli (cross-modal attentional entrainment) and processes of working memory updating (akin to the attentional blink). / Dissertation/Thesis / Ph.D. Psychology 2013

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<p>The psychological refractory period (PRP) paradigm has been used extensively to investigate the cognitive processing stages involved in dual-task performance. Interpretations of PRP data have often attributed the difficulty in simultaneously performing two cognitive tasks to a strict serial processing bottleneck in the response selection stage. However, a number of studies have also demonstrated backward response compatibility effects (BCEs) on Task 1 reaction time in dual-task performance, which suggest that response information for Task 2 may be activated in parallel with Task 1 response selection. The goal of this thesis was to examine the nature of the Task 2 processing that operates in parallel with Task 1 response selection in a PRP task, and to consider the implications of this parallel processing for models of dual-task performance. The results of the empirical studies presented here provide converging evidence that the BCE represents automatically activated response information for Task 2 acting on Task 1 response selection. This Task 2 response information can also contribute to Task 2 performance. Models of dual-task performance must account for both the parallel activation of response information and the serial selection of a response for each task.</p> / Doctor of Philosophy (PhD)

Dual task studies have found that Task 2 response information is activated during Task 1 response selection, and can have a priming effect on Task 1. This is called the backward compatibility effect (BCE). Giammarco et al. (2016) found that single-task practice of Task 2 in the context of a random, filler task (Practice-T2 condition) extinguished BCE development in a subsequent dual-task. On the other hand, practicing Task 2 in the context of Task 1 (Practice-Both condition) promoted BCE development in subsequent dual-tasks. Experiment 1a sought to replicate this context-specific disruption of BCE development by presenting participants with a single-task practice phase where they practiced Task 2 along with a filler task, and then observed BCE development in a subsequent dual-task phase. Experiment 1b addressed a counterbalancing issue in Experiment 1a. Experiment 2 was an exact replication of the Practice-T2 condition used in Giammarco et al. (2016). Overall, we conceptually replicated the context-specific disruption of BCE in Experiment 2, but not in Experiments 1a and 1b. Further study is warranted to determine the effect of specific response features on the learning context of Task 2. / Thesis / Master of Science (MSc) / Backward compatibility effects (BCEs) have been consistently observed in dual task paradigms. BCEs occur when Task 1 and Task 2 response information are congruent: participants respond faster to Task 1 when the two tasks require congruent responses than when they require incongruent ones. This suggests that there is some parallel processing of Task 2 while performing Task 1. The purpose of this study was to explore the episodic account of BCE development. Since episodic memories are context-specific, BCEs should also be context-specific, according to the episodic account. By manipulating the context of Task 2 learning, we tested whether this affected subsequent BCE development. Our findings suggest that context-specific disruption of BCE development is possible, but depends on other factors as well.

<p>Research on backward response compatibility effects (Task 2-to-Task 1 response priming) in the Psychological Refractory Period (PRP) paradigm has suggested that compatibility effects arise from episodic representations of Stimulus-Response (S-R) pairings (Hommel & Eglau, 2002). However, more recent work suggests that these effects are mediated by S-R rules held online in working memory during dual task performance (Ellenbogen & Meiran, 2008). We sought to dissociate these accounts. In Experiment 1, we observed the development of backward response compatibility effects over time in a common PRP task, following varying degrees of prior single task practice of the PRP component tasks. In Experiment 2, we trained participants on a PRP dual task, and then switched Task 2 to one of three different tasks with variable response mapping overlap with the original Task 2, before finally reverting back to the original PRP tasks. Backward response compatibility effects appeared initially, were abolished during the subsequent interference phase, and then reappeared with the original PRP task. Despite equivalent overall performance across conditions suggesting successful task rule instantiation in working memory to guide task performance, backward response compatibility effects were selectively absent in conditions where current S-R rules were mapped in conflict with prior S-R experiences within the experiment. Both experiments provide evidence in favour of an episodic account of backward response compatibility effects, in which prior learning influences subsequent performance in contextually relevant situations. Implications for the understanding of backward response compatibility mechanisms and parallel processing in the PRP paradigm are discussed.</p> / Master of Science (MSc)

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The monitoring of cognitive functions is central to the assessment and consecutive management of multiple sclerosis (MS). Though, especially cognitive processes that are central to everyday behavior like dual-tasking are often neglected. We examined dual-task performance using a psychological-refractory period (PRP) task in N = 21 patients and healthy controls and conducted standard neuropsychological tests. In dual-tasking, MS patients committed more erroneous responses when dual-tasking was difficult. In easier conditions, performance of MS patients did not differ to controls. Interestingly, the response times were generally not affected by the difficulty of the dual task, showing that the deficits observed do not reflect simple motor deficits or deficits in information processing speed but point out deficits in executive control functions and response selection in particular. Effect sizes were considerably large with d∼0.80 in mild affected patients and the achieved power was above 99%. There are cognitive control and dual tasking deficits in MS that are not attributable to simple motor speed deficits. Scaling of the difficulty of dual-tasking makes the test applied suitable for a wide variety of MS-patients and may complement neuropsychological assessments in clinical care and research setting.