Mixed-Method Precooling Enhances Self-Paced 20-km Cycling Time-Trial Performance When Apparent Temperature Is >46 °C but May Not Be a Priority in <46 °C.

PURPOSE: Precooling (PreC) may only benefit performance when thermal strain experienced by an individual is sufficiently high. We explored the effect of mixed-method PreC on 20-km cycling time-trial (CTT) performance under 3 different apparent temperatures (AT). METHODS: On separate days, 12 trained or highly trained male cyclists/triathletes completed six 20-km CTTs in 3 different ATs: hot-dry (35 °C AT), moderately hot-humid (40 °C AT), and hot-humid (46 °C AT). All trials were preceded by 30 minutes of mixed-method PreC or no PreC (control [CON]). RESULTS: Faster 2.5-km-split completion times occurred in PreC compared with CON in 46 °C AT (P = .02), but not in 40 °C AT (P = .62) or 35 °C AT (P = .57). PreC did not affect rectal and body temperature during the 20-km CTT. Skin temperature was lower throughout the CTT in PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = 1.00) and 35 °C AT (P = 1.00). Heart rate had a greater rate of increase during the CTT for PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = .57) and 35 °C AT (P = 1.00). Ratings of perceived exertion (P < .001) and thermal comfort (P = .04) were lower for PreC compared with CON in 46 °C AT only, while thermal sensation was not different between PreC and CON. CONCLUSION: Mixed-method PreC should be applied prior to 20-km CTTs conducted in hot-humid conditions (≥46 °C AT). Alternatively, mixed-method PreC may be a priority in moderately hot-humid (∼40 °C AT) conditions but should not be in hot-dry (∼35 °C AT) conditions for 20-km CTT.

Autonomous motivation promotes goal attainment through the conscious investment of effort, but mental contrasting with implementation intentions makes goal striving easier.

People with autonomous motives (e.g., personal importance) may use automated strategies to effortlessly sustain goal-directed behavior and overcome obstacles. We investigated whether conscious effort, ease of goal striving, physiological effort, and the number of obstacles encountered mediate relations between motives and goal attainment for a competitive cycling goal. Additionally, half the participants (n = 57) were trained in Mental Contrasting with Implementation Intentions (MCII) - a technique that facilitates development of goal-directed behavior - with remaining participants (n = 54) treated as controls. Conscious investment of effort mediated relations between autonomous motives and goal attainment. Subjective ease of goal striving and physiological effort did not. This result indicates that successful goal striving is not perceived as effortless for autonomously motivated individuals working on competitive goals. Conversely, MCII predicted a reduction in obstacles, which in turn was associated with easier goal striving but not goal attainment. Although MCII did not support goal attainment in the current study, its ability to minimize the influence of obstacles may still be useful for other types of goals or for sustaining long-term goal pursuit.

Stressor reflections, sleep, and psychological well-being: A pre-registered experimental test of self-distanced versus self-immersed reflections.

Evidence supports the effectiveness of cuing people to analyse negative autobiographical experiences from self-distanced rather than self-immersed perspectives. However, the evidence on which this expectation resides is limited largely to static snapshots of mean levels of cognitive and emotional factors. Via a pre-registered, randomised controlled trial (N = 257), we examined the differential effectiveness of self-distanced relative to self-immersed reflections on mean levels and within-person variability of sleep duration and quality as well as psychological well-being over a 5-day working week. Except for sleep quality, we found that reflecting from a psychologically distanced perspective, overall, was no more effective for mean levels and within-person variability of sleep duration, well-being, and stress-related factors than when the current self is fully immersed in the experiential reality of the event. We consider several substantive and methodological considerations (e.g., dosage, salience of stressor event) that require interrogation in future research via experimental and longitudinal observational methods.

Flow parsing and biological motion.

Flow parsing is a way to estimate the direction of scene-relative motion of independently moving objects during self-motion of the observer. So far, this has been tested for simple geometric shapes such as dots or bars. Whether further cues such as prior knowledge about typical directions of an object's movement, e.g., typical human motion, are considered in the estimations is currently unclear. Here, we adjudicated between the theory that the direction of scene-relative motion of humans is estimated exclusively by flow parsing, just like for simple geometric objects, and the theory that prior knowledge about biological motion affects estimation of perceived direction of scene-relative motion of humans. We placed a human point-light walker in optic flow fields that simulated forward motion of the observer. We introduced conflicts between biological features of the walker (i.e., facing and articulation) and the direction of scene-relative motion. We investigated whether perceived direction of scene-relative motion was biased towards biological features and compared the results to perceived direction of scene-relative motion of scrambled walkers and dot clouds. We found that for humans the perceived direction of scene-relative motion was biased towards biological features. Additionally, we found larger flow parsing gain for humans compared to the other walker types. This indicates that flow parsing is not the only visual mechanism relevant for estimating the direction of scene-relative motion of independently moving objects during self-motion: observers also rely on prior knowledge about typical object motion, such as typical facing and articulation of humans.

Heading perception from optic flow in the presence of biological motion.

We investigated whether biological motion biases heading estimation from optic flow in a similar manner to nonbiological moving objects. In two experiments, observers judged their heading from displays depicting linear translation over a random-dot ground with normal point light walkers, spatially scrambled point light walkers, or laterally moving objects composed of random dots. In Experiment 1, we found that both types of walkers biased heading estimates similarly to moving objects when they obscured the focus of expansion of the background flow. In Experiment 2, we also found that walkers biased heading estimates when they did not obscure the focus of expansion. These results show that both regular and scrambled biological motion affect heading estimation in a similar manner to simple moving objects, and suggest that biological motion is not preferentially processed for the perception of self-motion.

Concurrent processing of optic flow and biological motion.

The concurrent processing of optic flow and biological motion is crucial for navigating to a destination without colliding with others. Neuroimaging studies and formal models have provided evidence for distinct neural mechanisms involved in processing the 2 types of motion. It may, therefore, be possible to process both types of motions independently. To test for possible interferences at the behavioral level, we conducted a dual task paradigm in which we presented a point-light walker in a flow field that simulated forward motion. Observers judged both the articulation of the walker and the heading direction. We found that varying the difficulty of one task had no effect on the performance of the other task, arguing against interferences. Performance in the biological motion task was similar in dual and single task conditions. For the heading task, concurrence costs were observed when the heading task was difficult but not when it was easy. Concurrence costs did not depend on practice effects, effects of specific motor responses, and incidental processing of biological motion. In line with neuroimaging studies and formal models, our results argue not only for independent processing of optic flow and biological motion but also for concurrence costs affecting heading performance. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Heading Through a Crowd.

The ability to navigate through crowds of moving people accurately, efficiently, and without causing collisions is essential for our day-to-day lives. Vision provides key information about one's own self-motion as well as the motions of other people in the crowd. These two types of information (optic flow and biological motion) have each been investigated extensively; however, surprisingly little research has been dedicated to investigating how they are processed when presented concurrently. Here, we showed that patterns of biological motion have a negative impact on visual-heading estimation when people within the crowd move their limbs but do not move through the scene. Conversely, limb motion facilitates heading estimation when walkers move independently through the scene. Interestingly, this facilitation occurs for crowds containing both regular and perturbed depictions of humans, suggesting that it is likely caused by low-level motion cues inherent in the biological motion of other people.

Biological motion cues aid identification of self-motion from optic flow but not heading detection.

When we move through the world, a pattern of expanding optic flow is generated on the retina. In completely rigid environments, this pattern signals one's direction of heading and is an important source of information for navigation. When we walk towards an oncoming person, the optic environment is not rigid, as the motion vectors generated by the other person represent a composite of that person's movement, his or her limb motion, and the observer's self-motion. Though this biological motion obfuscates the optic flow pattern, it also provides cues about the movement of other actors in the environment. It may be the case that the visual system takes advantage of these cues to simplify the decomposition of optic flow in the presence of other moving people. The current study sought to probe this possibility. In four experiments self-motion was simulated through an environment that was empty except for a single, walking point-light biological motion stimulus. We found that by using biological motion cues, observers were able to identify the presence of self-motion despite the lack of stable scene information. However, when estimating heading based on these stimuli, the pattern of observer heading estimates could be approximately reproduced by computing the vector sum of the walker's translation and the stimulated self-motion. This suggests that though biological motion can be used to disentangle self-motion in ambiguous situations, optic flow analysis does not use this information to derive heading estimates.

Impairments in the Visual Processing of Global Biological Motion Cues in Down Syndrome.

Down syndrome (DS) is one of the most common chromosomal disorders and is often associated with a number of motor and cognitive impairments. Little research has been dedicated to investigating the perceptual abilities of individuals with DS. The visual processing of biological motion has been shown to be impaired in DS. It has been proposed that these impairments may stem from an inability to process the global patterns of full-body motion produced by a moving actor; however, this has not been explicitly investigated. We tested groups of participants with and without DS on a task requiring the visual discrimination of point-light walkers from spatially scrambled versions of point-light walkers. Participants with DS demonstrated poorer performance and slower reaction times on the task than healthy controls. From these results, we conclude that biological motion processing is impaired in DS and that this deficit is related to an inability to integrate global configural cues. In a second experiment, individuals with DS were able to discriminate the direction in which laterally translating walkers moved, suggesting that the global motion processing deficit observed in Experiment 1 is specific to biological motion recognition and does not generalise to other types of global motion.

Tolerance for local and global differences in the integration of shape information.

Shape is a critical cue to object identity. In psychophysical studies, radial frequency (RF) patterns, paths deformed from circular by a sinusoidal modulation of radius, have proved valuable stimuli for the demonstration of global integration of local shape information. Models of the mechanism of integration have focused on the periodicity in measures of curvature on the pattern, despite the fact that other properties covary. We show that patterns defined by rectified sinusoidal modulation also exhibit global integration and are indistinguishable from conventional RF patterns at their thresholds for detection, demonstrating some indifference to the modulating function. Further, irregular patterns incorporating four different frequencies of modulation are globally integrated, indicating that uniform periodicity is not critical. Irregular patterns can be handed in the sense that mirror images cannot be superimposed. We show that mirror images of the same irregular pattern could not be discriminated near their thresholds for detection. The same irregular pattern and a pattern with four cycles of a constant frequency of modulation completing 2π radians were, however, perfectly discriminated, demonstrating the existence of discrete representations of these patterns by which they are discriminated. It has previously been shown that RF patterns of different frequencies are perfectly discriminated but that patterns with the same frequency but different numbers of cycles of modulation were not. We conclude that such patterns are identified, near threshold, by the set of angles subtended at the center of the pattern by adjacent points of maximum convex curvature.