The limits of visual mass perception

The theory of direct perception suggests that observers can accurately judge the mass of a box picked up by a lifter shown in a point-light display. However, accurate perceptual performance may be limited to specific circumstances. The purpose of the present study was to systematically examine the factors that determine perception of mass, including display type, lifting speed, response type, and lifter's strength. In contrast to previous research, a wider range of viewing manipulations of point-light display conditions was investigated. In Experiment 1, we first created a circumstance where observers could accurately judge lifts of five box masses performed by a lifter of average strength. In Experiments 2–5, we manipulated the spatial and temporal aspects of the lift, the judgement type, and lifter's strength, respectively. Results showed that mass judgement gets worse whenever the context deviates from ideal conditions, such as when only the lifted object was shown, when video play speed was changed, or when lifters of different strength performed the same task. In conclusion, observers' perception of kinetic properties is compromised whenever viewing conditions are not ideal.     

Perception of Kinematic Characteristics in the Motion of Lifted Weight

It has been widely shown that human observers are able to perceive lifted weight from the observation of a point-light display of the lifter's action. In the experiments reported here, the kinematic information used by observers to perceive a lifted weight was determined. In Experiment 1, observers (N equals: 30) were able to identify weights (5, 10, 15, 20, and 25 kg) successfully by observing only the lift phase of the action. Other procedures, such as walking while holding the weight and placing the weight on a table, did not result in significantly improved estimations. In Experiment 2, the kinematic patterns used by 4 lifters with weights varying from 5 to 25 kg were examined. Changes in weight lifted resulted in changes in lift velocity, hip angle, and dwell time. In Experiment 3, in which 15 observers participated, these 3 kinematic variables were experimentally manipulated. The results indicated that observation was most significantly influenced by variations in lift velocity. The results are discussed in relation to kinematic specification of dynamics and heuristic approaches.     

Understanding individual differences in lifting mechanics: Do some people adopt motor control strategies that minimize biomechanical exposure

The movement strategy an individual uses to complete a lift can influence the resultant biomechanical exposure on their low back. We hypothesize that some lifters may choose a motor control strategy to minimize exposure to the low back, where others may not. Lower magnitudes of exposure to the low back coupled with less variability in lift-to-lift exposure and in features of movement strategy related to biomechanical exposure would support that such lifters consider minimizing exposure in their motor control strategy. We tested this hypothesis by investigating if differences in variability of low back exposure measures, as well as features of movement strategy related to resultant low back exposures differed across lifters. Twenty-eight healthy adults participated in the study where ten repetitions of a lifting task with the load scaled to 75% of participant's one-repetition maximum were completed. In all trials, whole-body kinematics and ground reaction forces were collected. Lifters were grouped as low, moderate or high relative exposure based on low back flexion angles and normalized L4/L5 extensor moments when lifting. Principal component analysis was used to identify independent movement strategy features, and statistical testing determined which features differed between high and low exposure lifts. Variability in low back exposures and movement features associated with relative biomechanical exposure were compared across lifter classifications. Significantly less variability was observed in low back exposures among the low exposure lifter group. Additionally, a trend towards lower variability in movement features associated with relative biomechanical exposure was also observed in low exposure lifters. These findings provide initial support for the hypothesis that some lifters likely define a motor control strategy that considers minimizing biomechanical exposure in addition to completing the lift demands. Future work should explore how state and trait-based factors influence an individual to consider biomechanical exposure within their motor control strategy in lifting.     

Expecting to lift a box together makes the load look lighter

The action abilities of an individual observer modulate his or her perception of spatial properties of the environment and of objects. The present study investigated how joint action abilities shape perception. Four experiments examined how the intention to lift an object with another individual affects perceived weight. In Experiments 1, 2a, and 2b, participants judged the perceived weight of boxes while expecting to lift them either alone or with a co-actor. In Experiment 3, the co-actor was healthy or injured. Participants intending to lift a box with a co-actor perceived the box as lighter than participants intending to lift the same box alone, provided that the co-actor appeared healthy and therefore capable of helping. These findings suggest that anticipated effort modulates the perception of object properties in the context of joint action. We discuss implications for the role of action prediction and action simulation processes in social interaction.     

The relative influences of movement kinematics and extrinsic object characteristics on the perception of lifted weight

Humans are able to perceive unique types of biological motion presented as point-light displays (PLDs). Thirty years ago, Runeson and Frykholm (Human Perception and Performance, 7(4), 733, 1981, Journal of Experimental Psychology: General, 112(4), 585, 1983) studied observers’ perceptions of weights lifted by actors and identified that the kinematic information in a PLD is sufficient for an observer to form an accurate perception of the object weight. However, research has also shown that extrinsic object size characteristics also influence the perception of object weight (Gordon, Forssberg, Johansson, & Westling in Experimental Brain Research, 83(3), 477–482, 1991). This study addresses the relative contributions of these two types of visual information to observers’ perceptions of lifted weight, through an experiment in which participants viewed an actor lifting boxes of various sizes (small, medium, or large) and weights (25, 50, or 75 lb) under four PLD conditions—box-at-rest, moving-box, actor-only, and actor-and-box—and one full-vision video condition, and then provided a weight estimate for each box lifted. The results indicated that lift kinematics and box size contributed independently to weight perception. Interestingly, the most robust weight differentiations were elicited in the conditions in which both types of information were presented concurrently, despite their converse natures. Furthermore, full-vision video presentation, which contained visual information beyond kinematics and object information, elicited the best estimates.     

Psychometric properties and construct validity of the Muscle Appearance Satisfaction Scale among Hungarian men

Limited studies have evaluated the psychometric properties of the Muscle Appearance Satisfaction Scale (MASS), a measure of muscle dysmorphia, in different cultures and languages. The aims were to examine the psychometric properties of the Hungarian version of the MASS (MASS-HU), and to investigate its relationship with self-esteem and exercise-related variables. Two independent samples of male weight lifters (ns = 289 and 43), and a sample of undergraduates (n = 240) completed the MASS, Eating Disorder Inventory, and Rosenberg Self-esteem Scale. Exploratory factor analysis supported the original five-factor structure of the MASS only in the weight lifter sample. The MASS-HU had excellent scale score reliability and good test-retest reliability. The construct validity of the MASS-HU was tested with multivariate regression analyses which indicated an inverse relationship between self-esteem and muscle dysmorphia. The 18-item MASS-HU was found to be a useful measure for the assessment of muscle dysmorphia among male weight lifters.     

Self-serving biases: The role of perspective-taking

This research explores the role of perspective taking in self-serving biases. Assisted by a confederate, 80 subjects performed an impression-formation task and were given either success or failure bogus feedback. One week later, half of the subjects watched their performance on videotape and provided causal attributions (‘observers’). The other half simply gave causal attributions (‘actors’). Thus, the experiment employed a modified version of the actor/observer paradigm with one group of subjects taking the perspective of observers (‘observers’) and one group of subjects keeping their original perspective (‘actors’). The aim of this study was to test whether the change of perspective would increase dispositional causal attributions both in success and failure conditions. Results showed that subjects gave greater causal weight to internal factors (ability, effort) and less causal weight to external factors (task characteristics, collaboration with the partner) in the success than in the failure condition. Moreover, in a direct comparison task, subjects attributed a greater percentage of responsibility to themselves than to their partner in the success than in the failure condition. However, the type of perspective produced no significant effects, but showed an attenuation of self-serving biases for observers as compared to actors. A motivational explanation of the results is proposed.     

Observation of action and autonomic nervous system responses

Observing somebody performing an action has been shown to elicit neuronal activity in the premotor cortex. This paper investigated physiological effect of observing an effortful action at the peripheral level. As Autonomic Nervous System responses reflect central nervous system processes such as movement planning and programming, it was expected that observing an action would elicit a pattern of ANS responses matching those recorded during actual movement. 12 male subjects, ages 23 to 28 years (M = 25.5, SD = 1.9), were selected as they were experienced in weight lifting. They were asked to observe a squat movement followed by returning to the upright position under 3 different conditions: (i) observation of actual movement performed by somebody else, (ii) observation of a video of the subject himself (first-person video), and (iii) observation of a video of somebody else performing the same movement (third-person video). Moreover, each movement was observed when performed at 50% and 90% of each participant's personal best mark (% of the highest weight which could be lifted). Three ANS parameters were continuously recorded: skin resistance, temperature and heart rate. ANS responses varied as a function of movement intensity: autonomic responses recorded during movement observation at 90% were significantly higher and longer than those recorded during movement observation at 50%. Thus, autonomic responses were linked to the amount of observed effort. Conversely, no difference was found among the three conditions of observation. ANS responses from observation of actual movement were shown to resemble those recorded under the two conditions of video observation.     

Reinforcement of human observing behavior by a stimulue correlated with extinction or increased effort

Young men pulled a plunger on mixed and multiple schedules in which periods of variable-interval monetary reinforcement alternated irregularly with periods of extinction (Experiment 1), or in which reinforcement was contingent on different degrees of effort in the two alternating components (Experiment 2). In the baseline conditions, the pair of stimuli correlated with the schedule components could be obtained intermittently by pressing either of two observing keys. In the main conditions, pressing one of the keys continued to produce both discriminative stimuli as appropriate. Pressing the other key produced only the stimulus correlated with variable-interval reinforcement or reduced effort; presses on this key were ineffective during periods of extinction or increased effort. In both experiments, key presses producing both stimuli occurred at higher rates than key presses producing only one, demonstrating enhancement of observing behavior by a stimulus correlated with the less favorable of two contingencies. A control experiment showed that stimulus change alone was not an important factor in the maintenance of the behavior. These findings suggest that negative as well as positive stimuli may play a role in the conditioned reinforcement of human behavior.     

Integration of stimulus dimensions in perception and memory: composition rules and psychophysical relations

A series of five experiments used the method of magnitude estimation to assess how height and width are integrated in perceptual and in memorial judgments of area. Separate groups of subjects estimated the areas of perceived or remembered rectangles produced by a symmetrical 4 X 4 factorial design of height and width. Additional independent groups of observers made area judgments, based on special mixes of perceptual and memorial information referring to the height and width components of the to-be-judged rectangles. Both perceptual and memory data obeyed the bilinear interaction prediction of the normative multiplicative model. The relation between perceived and actual area as well as the relation between remembered and actual area could both be described by a compressive power function, with the exponent being reliably smaller for remembered than for perceived area. These results seem to imply a principle of integration rule invariance across perceptual and memorial estimates of a given set of stimuli, in conjunction with characteristically different valuation operations.     

On the theoretical error bound for estimating psychometric functions

The theoretical limits to the amount of error, or the Cramer-Rao bounds, were derived for estimating psychometric functions. These theoretical error bounds were compared with the variability of psychometric functions estimated from human as well as computer-simulated observers. For the simulated observers, due to the limited efficiency of the sampling strategies, including the placement of the signals and the distribution of the trials, the variances of the estimated parameters are seven times the theoretical bound for threshold and 22 times that for slope. For the human observers, the variance is 18 times the theoretical bounds for threshold and 80 times that for slope. Therefore, a major portion of the variances (60% for threshold and 73% for slope) for the human observers is associated with factors other than sampling strategies. Further improvement of the accuracy for estimating psychometric functions will depend on not only optimizing the sampling strategy, but also better understanding the various sources of error related to the behavior of human observers.     

Body-based perceptual rescaling revealed through the size-weight illusion

An embodied approach to the perception of spatial layout contends that the body is used as a 'perceptual ruler' with which individuals scale the perceived environmental layout. In support of this notion, previous research has shown that the perceived size of objects can be influenced by changes in the apparent size of hand. The size-weight illusion is a well known phenomenon, which occurs when people lift two objects of equal weight but differing sizes and perceive that the larger object feels lighter. Therefore, if apparent hand size influences perceived object size, it should also influence the object's perceived weight. In this study, we investigated this possibility by using perceived weight as a measure and found that changes in the apparent size of the hand influence objects' perceived weight.     

Learned patterns of action-effect anticipation contribute to the spatial displacement of continuously moving stimuli

When participants control the horizontal movements of a stimulus and indicate its vanishing point after it unexpectedly vanishes, the perceived vanishing point is displaced beyond the actual vanishing point, and the size of the displacement is directly related to the action-effect anticipation one has to generate to successfully control the stimulus. The present experiments examined whether learning a pattern of action-effect anticipation would later impact one's perception of moving stimuli. While 1 participant (the controller) controlled a dot's movements across a computer screen, another (the observer), who could neither see nor hear the controller, watched the dot's movements on a separate monitor. When the dot unexpectedly vanished, the observer indicated the vanishing point. After 40 trials, participants switched roles. While serving as observers, all participants generated forward displacements, but those who did so after acquiring control experience produced larger displacement. Subsequent experiments indicated the larger displacement was due to action-effect anticipation the participants learned while either controlling the dot or observing another do so.     

Body weight and body image among college women: perception, cognition, and affect

This study examined the relations between body weight and multiple parameters of body image in a nonclinical sample. Thirty-six female undergraduate students with stable body weights served as subjects; 12 were underweight, 12 were normal weight, and 12 were overweight, as determined using recent normative tables. Each subject responded to a general weight information questionnaire and to the Body-Self Relations Questionnaire, a standardized instrument assessing affective, cognitive, and behavioral components of appearance-related body image. A newly developed apparatus and procedure for estimating body size, the Body Image Detection Device, was utilized for perceptual and cognitive measures of body image. Each subject estimated and also subjectively appraised the width of her own body at five points and that of a realistic female mannequin. A caliper was used to record actual widths, and a standard laboratory scale and rule measured weight and height. The general finding of the study was that the perceptual, affective, and cognitive components of body image differed as a function of body weight, but the nature of the differences varied with the measure employed. The pattern of results for the perceptual measure suggest a cautious view of its reliability and validity. The multidimensional approach of our study, in marked contrast to earlier fractionated studies, offers a more integrated perspective on body image and provides new directions for future research.     

Body Weight and Body Image Among College Women: Perception,Cognition, and Affect

This study examined the relations between body weight and multiple parameters of body image in a nonclinical sample. Thirty-six female undergraduate students with stable body weights served as subjects; 12 were underweight, 12 were normal weight, and 12 were overweight, as determined using recent normative tables. Each subject responded to a general weight information questionnaire and to the BodySelf Relations Questionnaire, a standardized instrument assessing affective, cognitive, and behavioral components of appearance-related body image. A newly developed apparatus and procedure for estimating body size, the Body Image Detection Device, was utilized for perceptual and cognitive measures of body image. Each subject estimated and also subjectively appraised the width of her own body at five points and that of a realistic female mannequin. A caliper was used to record actual widths, and a standard laboratory scale and rule measured weight and height. The general finding of the study was that the perceptual, affective, and cognitive components of body image differed as a function of body weight, but the nature of the differences varied with the measure employed. The pattern of results for the perceptual measure suggest a cautious view of its reliability and validity. The multidimensional approach of our study, in marked contrast to earlier fractionated studies, offers a more integrated perspective on body image and provides new directions for future research.     

Mapping the zone of eye-height utility for seated and standing observers

In a series of experiments, we delimited a region within the vertical axis of space in which eye height (EH) information is used maximally to scale object heights, referred to as the "zone of eye height utility" (Wraga, 1999b Journal of Experimental Psychology, Human Perception and Performance 25 518-530). To test the lower limit of the zone, linear perspective (on the floor) was varied via introduction of a false perspective (FP) gradient while all sources of EH information except linear perspective were held constant. For seated (experiment 1a) observers, the FP gradient produced overestimations of height for rectangular objects up to 0.15 EH tall. This value was taken to be just outside the lower limit of the zone. This finding was replicated in a virtual environment, for both seated (experiment 1b) and standing (experiment 2) observers. For the upper limit of the zone, EH information itself was manipulated by lowering observers' center of projection in a virtual scene. Lowering the effective EH of standing (experiment 3) and seated (experiment 4) observers produced corresponding overestimations of height for objects up to about 2.5 EH. This zone of approximately 0.20-2.5 EH suggests that the human visual system weights size information differentially, depending on its efficacy.     

Training children's self-control: A field experiment in self-monitoring and goal-setting in the classroom

A field experiment investigated the effects of training in self-monitoring and goal-setting skills on classroom study behavior and academic achievement among elementary school students in an individualized mathematics program. In the Self-Monitoring Conditions, students were shown a simple system for observing and maintaining daily records of their own study behavior during their math classes; orthogonally, in the Goal-Setting Conditions, students were shown a simple method of setting and recording daily performance goals during their math classes. Exposure to self-monitoring procedures produced significant increases in both appropriate study behavior and in actual achievement in the mathematics program, while exposure to goal-setting procedures had no effect on either study behavior or academic achievement. Nor, contrary to expectation, did exposure to the goal-setting instructions enhance the effectiveness of the self-monitoring system. The implications of these results in terms of implicit and explicit models of self-reinforcement processes were discussed.     

Spatial balance of color triads in the abstract art of Piet Mondrian

We examined the interactive contribution of the color and size of the three areas occupied by the primary colors red, yellow, and blue in adaptations of abstract compositions by Mondrian to the perceived weight of the areas and the location of the balance centers of the compositions. Thirty-six art stimuli were created by experimentally changing the colors in the three areas of six original works so that the resulting five variations and the original constituted the six possible spatial arrangements of the three colors in the three locations. In experiment 1, design-trained and untrained participants determined the location of the balance center of each composition seen on a computer screen and rated the apparent weight or heaviness of each color area. In experiment 2, untrained participants determined the location of the balance centers of the compositions when projected to their actual size. It was found that, for both trained and untrained participants, the perceived weight of a color, especially red and yellow, varied as a function of the size of the area it occupied. Furthermore, participants in both experiments perceived shifts in the locations of the balance centers between the originals and their altered versions. Only the trained participants, however, perceived significant shifts in balance centers among the five variations of the compositions, demonstrating their superior sensitivity to the contribution of color to balance structure. Taken together, the findings demonstrate the existence of a color-area-weight relationship among color triads in abstract displays and the influence of this relationship on color balance in abstract compositions.     

Big Five personality traits contribute to prosocial responses to others’ pain

ObjectivesTwo studies examined whether observers’ personality traits contribute to prosocial responses to others’ facial expression of pain. Experiment 1 examined the personality traits that could account for observers’ variability in estimating others’ pain intensity. Experiment 2 questioned to what extent the contribution of personality traits on inclination to help people in pain depend on observers’ beliefs about pain’ characteristics.Method59 (experiment 1) and 76 (experiment 2) participants observed to 3-D realistic synthetic face movements mobilizing action units of pain, in order to estimate others’ pain. In experiment 2, painful localizations (e.g., chest, hand) were also manipulated. In each experiment, Big Five personality traits were assessed.ResultsExperiment 1 revealed that agreeableness and conscientiousness contributed to observers’ pain estimates across the increase of facial expression intensity. Experiment 2 showed that conscientiousness contributed to observers’ judgments whatever pain’ characteristics. Neuroticism was only salient for pain referring to life-threatening pain.ConclusionProsocial response to others’ pain depends on agreeableness, conscientiousness and neuroticism. However, these links are modulated by the pain behavior elicited and observers’ belief about the characteristic of pain.     

Exercise dependence and the drive for muscularity in male bodybuilders,power lifters,and fitness lifters

Researchers have hypothesized differences in exercise dependence and drive for muscularity between bodybuilders and power lifters, while others have not found the predicted differences. This study assessed 146 weight lifters (bodybuilders, n = 59; power lifters, n = 47; fitness lifters, n = 40) on the Exercise Dependence Scale, Bodybuilding Dependence Scale, and the Drive for Muscularity Scale. Results showed that bodybuilders and power lifters were significantly higher than fitness lifters on EDS Total, 7 EDS scales, and the 3 BDS scales. In contrast, power lifters were found to be significantly higher on DMS Total and DMS Behavior scales than bodybuilders. The regression results suggest that exercise dependence may be directly related to the drive for muscularity.