Human behavior relies on the accumulation of task-relevant information to narrow the range of possible responses to a single response. How do we utilize advance information that can help us select and prepare responses to a task? How is this performance benefit facilitated in the brain? Previous literature suggests a subset of brain regions involved in cue-specific processing. We investigated how informative cues affect brain processing. Specifically, to what extent is activity modulated for stimulus-related and response-related cues versus neutral cues in control- and processing-related regions? Participants made manual responses to the identity of face or place stimuli in a variation of the response cuing paradigm while fMRI BOLD signal was recorded. Prior to the stimulus, a letter cue indicating the upcoming stimulus type (face or place) or response hand (left or right) or a neutral cue was presented. We proposed three hypotheses: 1) control-related activity (e.g., prefrontal, parietal) would increase for cued vs. uncued trials; 2) activity in face and place processing regions and left and right premotor regions would activate for their respective cues, although all cues were letters; and 3) stimulus processing regions would also be activated by response cues, and vice versa.

<p> The binary choice Fast Guess Model of Ollman and Yellott was generalized to a multiple choice model and six subjects were run in a choice reaction time task to test the model. Stimulus set sizes of two, four and six were used and response accuracy and speed motivation was manipulated through specific instructions which were changed from trial to trial. Three different motivational instructions were used. In all cases, subjects were to respond with maximum accuracy but were also told on each trial to either disregard the duration of their response, respond within 440 milliseconds or respond within 300 milliseconds.</p> <p> The generalized Fast Guess Model was rejected because response time parameters of the SCR state were found to change across response accuracy-speed motivation instructions and across stimulus set sizes. Implications of these results for other classes of models were also discussed.</p> / Thesis / Doctor of Philosophy (PhD)

No description available.

This dissertation examines the impact of stimulus and response similarity on response selection. Traditional models of response selection invoke a central processor that operates like a look-up table by matching the perceptually classified stimulus (e.g., green square) to the specified response (e.g., right button press). The look-up property of response selection affords the system the ability to map any stimulus onto any response, even if that stimulus-response has never been paired before. Under such an approach, the degree of perceptual similarity or dissimilarity that exists among stimuli in the environment should have little effect on central operations, the similarity or dissimilarity of the motor response executed in response to a stimulus should not influence response selection, and no interaction between stimulus and response features is permitted, given that stimulus features affect the encoding process, and response features affect the output process, but not response selection itself. Eight studies examine the influence of stimulus and response similarity during response selection. The first two experiments establish the interaction across different task demands between stimulus and response similarity. The interaction was not the result of perceptual difficulty (Experiment 3) and was extended to a new set of stimuli (Experiment 4). A consequence of the design in Experiments 1 - 4 was that response condition was confounded with response configuration. In one of the response conditions the target location had three competitors on one side of it compared to the other condition where the target had one competitor on one side and two others on the other side. Experiments 5 and 6 examined the separate roles that response configuration and response metrics had on the interaction between stimulus and response similarity. The mechanism that produced the interaction was the result of competition between partially activated stimulus-response alternatives. Experiments 7 and 8 further explored the role of competition during response selection by turning to traditional response selection methodologies that introduce competition through either the presentation of irrelevant stimulus information or through presenting the stimulus along an irrelevant spatial dimension. These data have broad implications for models of RS. To account for the ability to pair any stimulus modality with any response modality dominant accounts of RS assume that central operations are performed by a generic set of processes that operate over representations that are stripped of metric information (amodal representations). Response selection works as a look-up table that receives a categorized stimulus as an input and returns an abstract response code as output. This type of model cannot produce an interaction between stimulus and response similarity and thus, the present data provide a serious challenge to these types of models. Finally, the data provide evidence that the metric relationship between stimuli and response matter and influence response selection. The co-activation of stimulus-response alternatives are at a level of representation that includes both stimulus and response properties. A framework is presented that captures key aspects of the data.

For nearly two decades researchers have been interested in identifying what specifically is learned when individuals learn a sequence (e.g., sequence of stimuli, sequence of motor movements, etc.). Despite extensive research in the area, considerable controversy remains surrounding the locus of learning. There are three main theories concerning the nature of spatial sequence learning: sequence learning is purely perceptual, sequence learning includes a motor component and sequence learning is based on stimulus-response (S-R) rules. The present studies sought to disentangle these theories by demonstrating that sequence learning has both a perceptual and motor component and that altering S-R rules alone disrupts sequence learning. Experiment 1 results fully supported this S-R rule theory of sequence learning. Experiment 2 results provided only partial support for this theory, though the data were also inconsistent with both of the other accounts.

<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)

<p>Distinctions between set- and element-level compatibility have been made regarding stimulus-response compatibility (SRC) effects. Prior research has revealed a relationship between these two types of compatibility such that an increase in set-level effects results in an analogous increase in element-level effects. There are different ways that location information can be conveyed visually: location-words (“left” and “right”), directionalarrows (pointing left and right), and physical-locations (stimuli appearing in the left or right areas of the visual field). Set-level compatibility is higher for location-words paired with vocal “left”-“right” responses than for the other two stimulus modalities, and vice versa for pairings with left-right keypress responses, and the element-level compatibility effects differ in size accordingly.<br></p><p>My dissertation research focused on examining set- and element-level compatibility effects within the saccadic eye-movement system. These effects were considered within the dimensional overlap framework proposed by Kornblum, Hasbroucq, and Osman (1990), according to which the element-level mapping effects are an increasing function of set-level compatibility. All experiments were conducted using introductory psychology students. <br></p><p>In Experiment 1, participants responded using a left-right unimanual joystick movement or eye movement to a location-word or physical-location stimulus. In addition to an analysis of variance (ANOVA) of mean reaction time (RT) and response accuracy for the respective conditions, compatibility effects across the RT distribution were investigated by dividing trials into quantiles. Experiment 1 produced a set-level compatibility effect for the congruent mapping: Eye-movement responses (rather than joystick movements) were found to be relatively more compatible with physical-location stimuli than with location-word stimuli. In addition, the high set-level compatibility conditions exhibited a larger element-level mapping effect than the low set-level compatibility conditions. RT distribution analysis showed that both eye- and joystickmovements yielded a steadily increasing element-level mapping effect across bins, except for physical-location stimuli mapped to joystick responses, for which the function was flat. <br></p><p>In Experiment 2, the location-word stimuli used in Experiment 1 were replaced by directional-arrow stimuli. Eye movements (and not joystick movements) showed larger set- and element-level SRC effects when paired with physical-location stimuli than with directional-arrows. As in Experiment 1, the physical-location stimuli paired with eyemovement responses demonstrated an increase in the element-level mapping effect across the RT distribution. However, for the three other three set-level pairings, the elementlevel mapping effects were relatively constant across the RT distribution. This pattern further indicates a preferential benefit for eye movements paired with physical-location stimuli.<br></p><p>Experiment 3 directly compared the location-word stimuli used in Experiment 1 and the directional-arrow stimuli used in Experiment 2. The element-level mapping effect was larger for location-words than for directional-arrows, but both types of stimuli produced similar interaction patterns regarding the set-level manipulation. That is, the differences between each response modality and stimulus type produced similar patterns of element-level mapping effect differences. The location-word stimuli produced consistently large effects and served as a driving factor across the set-level comparisons. The location-words showed a large increase in element-level mapping effect across the RT distribution compared to only a small increase for the directional-arrows, which in both cases did not differ between eye- and joystick-movement responses.<br></p><p>Together the three experiments provide support for the hypothesis that eyemovement responses to physical-location stimuli are a unique, highly optimal set-level pairing relative to location-words or directional-arrows denoting spatially relevant location. In the context of a continuum outlining the relative position of different response and stimulus pairings, the results imply that eye-movement responses are similar in compatibility to joystick movements, except for the specific pairing with physical-location stimuli. <br></p><p>The results offer some support for Kornblum et al.’s (1990) account that suggests a tightly coupled relationship between set- and element-level compatibility effects. Not only do the results provide understanding about the existence of compatibility effects within the saccadic system, they allow for some considerations about how attention is allocated preferentially to certain stimuli rather than others. They also enable predictions about similar underlying mechanisms that might be involved in saccadic and manual response modalities. Taken together, it seems that the eye-movement system adheres to conventional notions about motoric behavior; however, it also has its own unique properties that make it highly tuned to exogenously guided stimuli. <br></p>

In open skill sports and other tasks, decision-making can be as important as physical performance. Whereas many studies have investigated visual perception there is little research on auditory perception as one aspect of decision making. Auditory localisation studies have almost exclusively focussed on underlying processes, such as interaural time difference and interaural level difference. It is not known, however, whether semantic spatial information contained in the sound is actually used, and whether it assists pure auditory localisation. The aim of this study was to investigate the effect on auditory localisation of spatial semantic information. In Experiment One, this was explored by measuring whole body orientation to the words &quotLeft", &quotRight", &quotBack", &quotFront" and &quotYes", as well as a tone, each presented from left right, front and back locations. Experiment Two explored the effect of the four spatial semantic words presented either from their matching locations, or from a position rotated 20 degrees anticlockwise. In both experiments there were two conditions, with subjects required to face the position indicated by the sound location, or the meaning of the word. Movements of the head were recorded in three dimensions with a Polhemus Fastrak system, and were analysed with a custom program. Ten young adult volunteers participated in each experiment. Reaction time, movement time, initial rotation direction, rotation direction at peak velocity, and the accuracy of the final position were the dependent measures. The results confirmed previous reports of confusions between front and back locations, that is, errors about the interaural axis. Unlike previous studies, many more back-to-front than front-toback errors was made. The experiments provided some evidence for a spatial Stroop interference effect, that is, an effect on performance of conflicting information provided by the irrelevant dimension of the stimulus, but only for reaction time and initial movement direction, and only in the Word condition. The results are interpreted using a model of the processes needed to respond to the stimulus and produce an orienting movement. They suggest that there is an asymmetric interference effect in which auditory localisation can interfere with localisation based on semantic content of words, but not the reverse. In addition, final accuracy was unaffected by any interference, suggesting that these effects are restricted to the initial stages of response selection.

The study of cognition as it relates to expert performance in sport is an area that has received increased attention over the last 25 years. This has been made possible by the fact that the domain of sport offers a rich and diverse setting in which to study cognition and its links to human performance, coupled with the abundant supply of highly practiced athletes providing unique opportunities to study these factors in a natural environment. The quality of on-field decision-making of expert athletes has received attention in a number of open-skill sporting codes, including basketball, field hockey and soccer. Decision-making quality of expert athletes in rugby union, as an invasive, open-skill sporting code, has not received the same amount of attention. Past studies on the decision-making of expert athletes in sport have tended to be carried through the isolation of specific cognitive functions and describing the role of each isolated function in the decision-making process. Given the speed at which decisions have to be made, as a result of time pressure, the isolation of cognitive functions yields valuable insights into the decision-making processes of expert athletes in competitive, on-field situations. While these cognitive functions can be studied in isolation, they do however form part of a bigger process that enables the expert athlete to make high quality on-field decisions. It is for this reason that it was decided to study these different functions in combination, as set out by the Information Processing Approach to cognitive functioning. According to this approach, the decision-making process consists on three main phases, namely that of Visual Search Strategies, Anticipation and Response Selection. This study was aimed at examining the quality of on-field decision-making of expert rugby players, as well as the influence of the competitive level at which rugby is played on decision-making quality. In order to achieve this goal it was necessary to develop a measurement instrument that can be used by expert rugby players to assess the quality of decisions made on the field of play. As it is difficult for outside observers to establish what players are thinking or focusing their attention on when making decisions on the field, it was necessary to design the instrument as a self-report measure of decision-making. By being made aware of one’s strong and weak points in on-field decision-making, expert rugby players can focus their attention on improving the underdeveloped facets of their game. The measurement of decision-making according to three distinct phases allows for increased accuracy in the identification of those cognitive areas that need improvement in order to improve overall playing ability. By changing the way the expert rugby player thinks about certain aspects of the game, most notably those aspects that the player has difficulty with, it becomes possible for the player to address these difficulties and make improvements wherever necessary. Copyright / Dissertation (MA)--University of Pretoria, 2008. / Psychology / unrestricted

Kognitive Kontrolle wird besonders in solchen Momenten deutlich, wenn eine geplante Handlung gestört wird. Weil zwei widerstreitende Verhaltenstendenzen gleichzeitig bestehen oder anlaufen, entsteht ein Konflikt. Experimentell können kognitive Konflikte beispielsweise mit dem Stroop-Paradigma hergestellt und untersucht werden (Stroop, 1935). Es ist dabei eine aktuelle Frage, wie Konflikte zeitlich verarbeitet werden und wo im Gehirn diese Verarbeitung geschieht. Zeitlich können Konflikte beispielsweise dann entstehen, wenn die Informationen des Stimulus abgerufen werden oder auch erst dann, wenn die intendierte Antwort tatsächlich für die Artikulation ausgewählt werden muss. Eine weiterführende Frage ist, ob sich die entsprechenden Ergebnisse für verschiedene Stroop-Varianten unterscheiden. In der vorliegenden Arbeit wurden diese Fragen systematisch für die Verarbeitung von Objekten und Zahlen mit zwei Varianten des Stroop-Paradigmas untersucht. In der vorliegenden Dissertation präsentiere ich Ergebnisse von Reaktionszeitstudien und fMRT-Experimenten zum zeitlichen Ablauf und zu neuronalen Substraten kognitiver Konflikte während der Verarbeitung von Objekten und Zahlen. Um die Konflikte zeitlich und räumlich lokalisieren zu können, wird die Abrufphase und die Antwortphase separat modelliert. Die Ergebnisse deuten darauf hin, dass die Konflikte eher während des Abrufs als bei der Antwortauswahl stattfinden. Außerdem wird geschlussfolgert, dass die Konflikte für Zahl- und Objektrepräsentationen nicht auf gemeinsamen neuronalen Substraten basieren. Die Ergebnisse meiner Reaktionszeitstudien und der MRT-Studien deuten also darauf hin, dass Konflikte bei der Verarbeitung von Objekten und Zahlen zwar einem ähnlichen zeitlichen Verlauf folgen, aber offenbar in unterschiedlichen neuronalen Netzwerken verarbeitet werden. / In daily life, we constantly have to adjust our goals and plans to changing task demands and internal needs. Our ability to balance the initiation and inhibition of our actions, and to solve resulting conflicts between them, is referred to as cognitive control. To study the processes of cognitive control, the Stroop Paradigm has become a popular tool (Stroop,1935). The Stroop Paradigm is frequently used to address central questions of cognitive control. It is, for instance, an open issue, where and when in the processing stream cognitive conflicts arise. Do they arise early, for example, during the retrieval of target and distractor? Or do they occur late, when the response is prepared for execution? Another debate is concerned with the question whether the findings agree for different Stroop variants (Van Maanen et al., 2009). In this dissertation I present research on the temporal characteristics and the neural substrates of cognitive conflicts during the processing of objects and numbers. To better understand the locus of the conflict, the retrieval phase and the response phase are modelled separately. The results from several reaction time studies and from two fMRI experiments speak to the issue that processing costs occur during retrieval, i.e., early in the processing stream, for both, object and number representations. The results further indicate that the processing of the conflict between target and distractor for number and object representations do not rely on common neural substrates. I will thus present the results from behavioural and functional imaging experiments, showing similar temporal patterns for the conflicts in both systems, but distinct underlying neural networks.