A behavioural analysis of "choking" in self-paced skills

This thesis is about "choking" in self-paced skills. Choking refers to ''the occurrence of inferior performance despite striving and incentives for superior performance" (Baumeister and Steinhilber, 1986, p. 361). Self-paced skills are skills in which performance is initiated by the athlete. This research set out to investigate the cause of choking in self-paced skills within the theoretical framework of behaviour analysis. The main focus of the research relates to the distinction between behaviour under the control of verbal antecedents (rule-governed behaviour) and behaviour that is shaped by its consequences (contingency-shaped behaviour). It was originally hypothesised that the insensitivity of rule-governed behaviour to changes in the contingencies of reinforcement could he beneficial in situations where these changes led to greater performance pressure. Specifically, it was predicted that performance under the control of verbal antecedents would be less susceptible to choking. In the first experiment, no support was found for the hypothesis and, furthermore, rule-governed performance appeared to be inferior to contingency-shaped performance in the early stages of acquisition. In light of these results, and after a detailed examination of the behaviour analysis distinction between these two forms of behaviour, evidence was presented which suggested that verbal control of the topography, or form, of behaviour would be likely to disrupt performance in self-paced skills. In subsequent experiments, it was found that using simple verbal cues was an effective means of preventing choking under pressure. It was hypothesised that the function of these cues was in preventing reinvestment of too many technical instructions in the moments before performance initiation. The assumptions upon which the reinvestment theory of choking is based were also examined with results providing general support for the theory but also suggesting that it needs to be refined to account for verbal antecedents that do not disrupt performance

Ocean and atmosphere feedbacks affecting AMOC hysteresis in a GCM

Theories suggest that the Atlantic Meridional Overturning Circulation (AMOC) can exhibit a hysteresis where, for a given input of fresh water into the north Atlantic, there are two possible states: one with a strong overturning in the north Atlantic (on) and the other with a reverse Atlantic cell (off). A previous study showed hysteresis of the AMOC for the first time in a coupled general circulation model (Hawkins et al. in Geophys Res Lett. doi: 10.1029/2011GL047208, 2011). In this study we show that the hysteresis found by Hawkins et al. (2011) is sensitive to the method with which the fresh water input is compensated. If this compensation is applied throughout the volume of the global ocean, rather than at the surface, the region of hysteresis is narrower and the off states are very different: when the compensation is applied at the surface, a strong Pacific overturning cell and a strong Atlantic reverse cell develops; when the compensation is applied throughout the volume there is little change in the Pacific and only a weak Atlantic reverse cell develops. We investigate the mechanisms behind the transitions between the on and off states in the two experiments, and find that the difference in hysteresis is due to the different off states. We find that the development of the Pacific overturning cell results in greater atmospheric moisture transport into the North Atlantic, and also is likely responsible for a stronger Atlantic reverse cell. These both act to stabilize the off state of the Atlantic overturning

Adipose Tissue as a Site of Toxin Accumulation

We examine the role of adipose tissue, typically considered an energy storage site, as a potential site of toxicant accumulation. Although the production of most persistent organic pollutants (POPs) was banned years ago, these toxicants persist in the environment due to their resistance to biodegradation and widespread distribution in various environmental forms (e.g., vapor, sediment, and water). As a result, human exposure to these toxicants is inevitable. Largely due to their lipophilicity, POPs bioaccumulate in adipose tissue, resulting in greater body burdens of these environmental toxicants with obesity. POPs of major concern include polychlorinated biphenyls (PCBs), polychlorinated dibenzo‐p‐dioxins and furans (PCDDs/PCDFs), and polybrominated biphenyls and diphenyl ethers (PBBs/PBDEs), among other organic compounds. In this review, we 1) highlight the physical characteristics of toxicants that enable them to partition into and remain stored in adipose tissue, 2) discuss the specific mechanisms of action by which these toxicants act to influence adipocyte function, and 3) review associations between POP exposures and the development of obesity and diabetes. An area of controversy relates to the relative potential beneficial versus hazardous health effects of toxicant sequestration in adipose tissue

Brain regions concerned with perceptual skills in tennis: An fMRI study

Sporting performance makes special demands on perceptual skills, but the neural mechanisms underlying such performance are little understood. We address this issue, making use of fMRI to identify the brain areas activated in viewing and responding to video sequences of tennis players, filmed from the opponent’s perspective. In a block-design, fMRI study, 9 novice tennis players watched video clips of tennis play. The main stimulus conditions were (1) serve sequences, (2) non-serve behaviour (ball bouncing) and (3) static control sequences. A button response was required indicating the direction of serve (left or right for serve sequences, middle button for non-serve and static sequences). By comparing responses to the three stimulus conditions, it was possible to identify two groups of brain regions responsive to different components of the task. Areas MT/MST and STS in the posterior part of the temporal lobe responded either to serve and to non-serve stimuli, relative to static controls. Serve sequences produced additional regions of activation in parietal lobe (bilateral IPL, right SPL) and in right frontal cortex (IFGd, IFGv), and these areas were not activated by non-serve sequences. These regions of parietal and frontal cortex have been implicated in a “mirror neuron” network in the human brain. It is concluded that the task of judgement of serve direction produces two different patterns of response: activations in MT/MST and STS concerned with primarily with the analysis of motion and body actions, and activations in parietal and frontal cortex associated specifically with the task of identification of direction of serve

Seeing the Bigger Picture: Susceptibility to, and Detection of, Deception

An extended time window was used to examine susceptibility to, and detection of, deception in rugby union. High-skilled and low-skilled rugby players judged the final running direction of an opponent ‘cutting’ left or right, with or without a deceptive sidestep. Each trial was occluded at one of eight time points relative to the footfall after the initial (genuine or fake) reorientation. Based on response accuracy, the results were separated into deception susceptibility and deception detection windows. Signal detection analysis was used to calculate the discriminability of genuine and deceptive actions (d’) and the judgement bias (c). High-skilled players were less susceptible to deception and better able to detect when they had been deceived, accompanied by a reduced bias towards perceiving all actions as genuine. By establishing the time window in which players become deceived it will now be possible to identify the kinematic sources that drive deception

Effect of Impact Location on the Response of Shuttle Wing Leading Edge Panel 9

The objective of this paper is to compare the results of several simulations performed to determine the worst-case location for a foam impact on the Space Shuttle wing leading edge. The simulations were performed using the commercial non-linear transient dynamic finite element code, LS-DYNA. These simulations represent the first in a series of parametric studies performed to support the selection of the worst-case impact scenario. Panel 9 was selected for this study to enable comparisons with previous simulations performed during the Columbia Accident Investigation. The projectile for this study is a 5.5-in cube of typical external tank foam weighing 0.23 lb. Seven locations spanning the panel surface were impacted with the foam cube. For each of these cases, the foam was traveling at 1000 ft/s directly aft, along the orbiter X-axis. Results compared from the parametric studies included strains, contact forces, and material energies for various simulations. The results show that the worst case impact location was on the top surface, near the apex

First Determination of the True Mass of Coronal Mass Ejections: A Novel Approach to Using the Two STEREO Viewpoints

The twin Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) COR2 coronagraphs of the Solar Terrestrial Relations Observatory (STEREO) provide images of the solar corona from two view points in the solar system. Since their launch in late 2006, the STEREO Ahead (A) and Behind (B) spacecrafts have been slowly separating from Earth at a rate of 22.5 degrees per year. By the end of 2007, the two spacecraft were separated by more than 40 degrees from each other. At this time, we began to see large-scale differences in the morphology and total intensity between coronal mass ejections (CMEs) observed with SECCHI-COR2 on STEREO-A and B. Due to the effects of the Thomson scattering geometry, the intensity of an observed CME is dependent on the angle it makes with the observed plane of the sky. From the intensity images, we can calculate the integrated line of sight electron density and mass. We demonstrate that is is possible to simultaneously derive the direction and true total mass of the CME if we make the simple assumption that the same mass should be observed in COR2-A and B

Reflection-impulsivity in athletes: A cross-sectional and longitudinal investigation

Reflection-impulsivity is a dimension of cognitive or decision-making style. We conducted two quasi-experimental studies to examine reflection-impulsivity in athletes using an information sampling task. In Study 1 (n = 108; Mage = 22.7 ± SDage = 1.42; 50% female), we used a cross-sectional design to compare performance across athletic expertise (super-elite, elite, amateur, novice or non-athlete) and sport type (external-paced or self-paced). In Study 2 (Time 1 n = 106; Mage = 21.32 ± SDage = 5.77; 53% female and Time 2 n = 64; Mage = 21.19 ± SDage = 5.12; 44% female), we examined changes in reflection-impulsivity across a 16-week playing season. Study 1 showed more accurate and more efficient performance as athletic expertise increased. Study 2 revealed better effectiveness and efficiency following sport participation, a 16-week playing season, most notably in elite-level performers. No sport-type differences were noted. Taken together, the studies demonstrate an association between reflection-impulsivity and athletic expertise, while also providing evidence that competitive sports participation leads to efficient decisions based on reflection, without sacrificing accuracy, which is often a consequence of impulsive decision-making