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PubMed1997

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 = 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.

kinematics↗
PubMed1992

Development of human precision grip. III. Integration of visual size cues during the programming of isometric forces.

Recent evidence has shown that visual and haptical size information can be used by adults to estimate the weight of the object, forming the basis of the force programming during precision grip (Gordon et al. 1991a, b,). The present study examined the development of the capacity to use visual size information. In the first experiment, 30 children (age 1-7 years) and 10 adults performed a series of lifts with two boxes presented in an unpredictable order. The boxes were equal in weight but unequal in size and were attached to an instrumented grip handle which measured the employed grip force, load force, position and their corresponding time derivatives. The isometric force development was not influenced by the box size before the age of 3. However, the children aged 3 years and older demonstrated greater visual influences on the force programming than adults. To determine more precisely when children began to use visual size information, a second experiment in which the size and weight covaried was performed on 15 children. Children still did not use the size information during the force programming until the later half of the third year. It is concluded that this ability, probably involving associative transformations between the size and weight of objects, emerges around one year after anticipatory control based on somatosensory information pertaining to the weight of the object.

Adolescent↗
PubMed2001

Sensorimotor prediction and memory in object manipulation.

When people lift objects of different size but equal weight, they initially employ too much force for the large object and too little force for the small object. However, over repeated lifts of the two objects, they learn to suppress the size-weight association used to estimate force requirements and appropriately scale their lifting forces to the true and equal weights of the objects. Thus, sensorimotor memory from previous lifts comes to dominate visual size information in terms of force prediction. Here we ask whether this sensorimotor memory is transient, preserved only long enough to perform the task, or more stable. After completing an initial lift series in which they lifted equally weighted large and small objects in alternation, participants then repeated the lift series after delays of 15 minutes or 24 hours. In both cases, participants retained information about the weights of the objects and used this information to predict the appropriate fingertip forces. This preserved sensorimotor memory suggests that participants acquired internal models of the size-weight stimuli that could be used for later prediction.

Adolescent↗
PubMed1998

Neural gain changes subserving perceptual acuity.

When small and large objects of equal weight are lifted, the small object feels heavier than the large one (the size-weight illusion) and requires more effort to lift (the size-effort illusion). It has been suggested that these illusions result from neural gain changes designed to maintain acuity under different working conditions. If this suggestion is correct, a given mass should produce a larger increase in perceived weight or effort when added to the small object. This was found to be the case.

Adolescent↗
PubMed1981

Wundt's views on sensations of innervation: a reevaluation.

It is sometimes stated that Wundt believed in the primacy of 'sensations of innervation' in the control of eye and limb position, to the exclusion of afferent feedback. Wundt's own statements on the subject are traced through the six editions of the Grundzüge: he believed that sensations of innervation were a contributory factor along with peripheral feedback; but in the fourth edition he dropped the term and subsumed them under 'central sensations of senses', because increased neurophysiological knowledge made a literal interpretation of the original term impossible. In the fifth edition he developed a more precise model of central processes, described as 'sensory costimulation', and an additional idea of 'reproduced' or conditioned sensations. He mentions clinical evidence on the perception of eye and limb position of weight by paralysed and other subjects. This evidence is discussed in relation to modern theories. It is concluded that Wundt's later theories have some similarities with modern "hybrid' theories of efference-contingent afference.

Afferent Pathways↗
PubMed2005

Visual properties of objects affect manipulative forces and respiration differently.

Previously, we demonstrated that the respiratory and motor systems responded differently following consecutive lifts of an object whose weight could be altered (lighter or heavier) without changing the object's visual properties. When the weight of the object was altered in a manner unpredictable to the subject, the motor system response reflected the previous weight of the object (light or heavy) while the respiratory system reflected responses seen when lifting the heavier object regardless of whether a lighter or heavier object was lifted previously. It is possible that the default pattern of the respiratory system was due to a lack of visual size cues, which are known to have robust affects on grasp control. To test this hypothesis, 14 seated subjects performed self-initiated alternating lifts with objects whose size and weight covaried such that the weight of the upcoming lift was known despite the weight of the object previously lifted. Following both consecutive and alternating trials, the load force was scaled to the weight of the object (e.g., the heavier the object the larger the force) while the volume was scaled only following the consecutive trials. This suggests that the load forces were developed entirely based on visual information while lung volume was not. In addition, we suggest that following the consecutive trials, the volume increased as the object's weight increased in an effort to assist with trunk stabilization by indirectly increasing intra-abdominal pressure.

Adult↗
PubMed2001

Relation of rifle stock length and weight to military rifle marksmanship performance by men and women.

15 male and 13 female soldiers participated in a study to examine the effects of sex, rifle stock length 117.8 cm, 22.3 cm, and 26.2 cm), and rifle weight (3.2 kg vs 3.8 kg) on military marksmanship performance. The Noptel simulator was used to assess marksmanship accuracy (proximity of shots to the target center) and precision (proximity of shots to one another regardless of proximity to the target center). There were no significant differences in either measure of marksmanship performance as a function of sex. Marksmanship accuracy was significantly better with the shortest rifle stock, and marksmanship precision was significantly better with the lighter rifle. Regardless of the sex of the shooter, stock length and weapon weight should be considered in any new combat rifle design as these results indicate they significantly affect marksmanship.

Adult↗
PubMed1993

The role of haptic versus visual volume cues in the size-weight illusion.

Three experiments establish the size-weight illusion as a primarily haptic phenomenon, despite its having been more traditionally considered an example of vision influencing haptic processing. Experiment 1 documents, across a broad range of stimulus weights and volumes, the existence of a purely haptic size-weight illusion, equal in strength to the traditional illusion. Experiment 2 demonstrates that haptic volume cues are both sufficient and necessary for a full-strength illusion. In contrast, visual volume cues are merely sufficient, and produce a relatively weaker effect. Experiment 3 establishes that congenitally blind subjects experience an effect as powerful as that of blindfolded sighted observers, thus demonstrating that visual imagery is also unnecessary for a robust size-weight illusion. The results are discussed in terms of their implications for both sensory and cognitive theories of the size-weight illusion. Applications of this work to a human factors design and to sensor-based systems for robotic manipulation are also briefly considered.

Adolescent↗
PubMed1999

The material-weight illusion revisited.

Experiment 1 documents modality effects on the material-weight illusion for a low-mass object set (58.5 g). These modality effects indicate that the material-weight illusion is principally a haptically derived phenomenon: Haptically accessed material cues were both sufficient and necessary for full-strength illusions, whereas visually accessed material cues were only sufficient to generate moderate-strength illusions. In contrast, when a high-mass object set (357 g) was presented under the same modality conditions, no illusions were generated. The mass-dependent characteristic of this illusion is considered to be a consequence of differing grip forces. Experiment 2 demonstrates that the enforcement of a firm grip abolishes the low-mass material-weight illusion. Experiment 3 documents that a firm grip also diminishes perceptual differentiation of actual mass differences. Several possible explanations of the consequences of increasing grip force are considered.

Adult↗
PubMed2000

Independence of perceptual and sensorimotor predictions in the size-weight illusion.

The smaller of two equally weighted objects is judged to be heavier when lifted. Here we disproved a leading hypothesis that this size-weight illusion is caused by a mismatch between predicted and actual sensory feedback. We showed that when subjects repeatedly lifted equally heavy large and small objects in alternation, they learned to scale their fingertip forces precisely for the true object weights and thus exhibited accurate sensorimotor prediction. The size-weight illusion nevertheless persisted, suggesting that the illusion can be caused by high-level cognitive and perceptual factors and indicating that the sensorimotor system can operate independently of the cognitive/perceptual system.

Adolescent↗
PubMed2002

Object motor representation and reaching-grasping control.

The following two competing hypotheses were tested in the present study. Is grasp guided by multiple representations of a single object, each of which codes a different grasp motor act according to the physical properties of that item? Conversely, is grasp guided by a single representation that codes all the possible affordances enabled by the object? Subjects reached different objects, but the object part used by subjects to grasp them was identical. In experiments 1 and 2, two familiar objects (fruits) which varied for size and shape were presented. Subjects grasped their stalks whose size and shape were equal. In experiments 3-7 the presented objects were geometrical solids, which varied, respectively, for weight, volume, intrinsic height, centre of mass and shape. Nevertheless, in all experiments the object portion where subjects' fingers grasped it had the same physical features. Finally, experiment 8 was a control experiment in which subjects reached and grasped equal handles of bells of the same shape, but different size. Volume, shape, and familiarity of the object influenced the grasp kinematics, even if the features of the grasped object part did not change. Variation in intrinsic object height and weight influenced final reach kinematics. Variation in centre of mass influenced neither grasp nor reach kinematics. Data are discussed in support of the hypothesis that a single object motor representation, which codes all the object affordances, is involved in grasp kinematic implementation.

Adult↗
PubMed1976

An experimental test of two mathematical models applied to the size-weight illusion.

Two quantitative models, which make different quantitative predictions for the amount of the size-weight illusion, were tested according to the psychophysical methods employed by the respective authors (magnitude estimation versus category ratings). Both models with their corresponding method were supported. This causes uncertainty over Anderson's chaim that the validity of both a model and the applied scale used is sufficiently test by the socalled joint testing procedure.

Humans↗
PubMed1979

Relationships among different stages of Piagetian tasks and spatial relations in adolescents.

High school students aged 15 through 19 years (N = 116) were administered three Piagetian type tasks (conservation of weight, paper and pencil tests of concrete-operational reasoning and formal-operational reasoning) and a measure of spatial relations (the Revised Minnesota Paper Form Board Test). While a path analysis showed there were logically expected relationships among the tasks, neither sex differences nor age differences were found on any of the measures.

Adolescent↗
PubMed1989

Narcosis has additive rather than interactive effects on discrimination reaction time.

A central feature of the impairment in performance produced by inert gas narcosis, which poses a threat to divers breathing compressed air, is a slowing of reaction time (RT). To investigate the locus of this slowing, the effects of 35% nitrous oxide on Crossman's confusion function were determined using line-length and weight discrimination tasks, with accuracy held constant. For both tasks narcosis slowed RT by increasing the intercept rather than the slope of Crossman's function. These results are interpreted in terms of additive factors method logic as being consistent with the predictions of the slowed processing model that has been proposed to account for the effects of narcosis on human performance.

Confusion↗
PubMed1999

Charpentier (1891) on the size-weight illusion.

This paper offers background for an English translation of an article originally published in 1891 by Augustin Charpentier (1852-1916), as well as a summary of it. The article is frequently described as providing the first experimental evidence for the size-weight illusion. A comparison of experiments on the judged heaviness of lifted weights carried out by Weber (1834) and by Charpentier (1891) supports the view that Charpentier's work deserves priority; review of other experimental studies on the size-weight illusion in the 1890s suggests that the idea that the illusion depended on "disappointed expectations," especially with respect to speed of lift, became dominant almost immediately following the publication of Charpentier's paper. The fate of this and other ideas, including "motor energy," in 20th-century research on the illusion is briefly described.

France↗
PubMed2004

Brain mechanisms for inferring deceit in the actions of others.

During social interactions, it is important to judge accurately whether a person is honest or deceitful. We often use nonverbal cues to infer whether others are trying to deceive us. Using functional magnetic resonance imaging, we studied subjects watching videos of actors lifting a box and judged whether or not the actors were trying to deceive them concerning the real weight of the box. When the subjects judged the actions as reflecting deceptive intention, there was activation of the amygdala and rostral anterior cingulate cortex. These areas were not activated when subjects made judgements about the beliefs rather than the intentions of others. We suggest that these activations reflect the observers' judgements of social intentions toward themselves and might reflect an emotional response to being deceived.

Adult↗
PubMed1984

The development of sensitivity to causally relevant dynamic information.

The present study examined whether younger observers (kindergartners, second graders, and fourth graders) could extract relative weight information from collisions and also lifting events, and if they could judge whether collisions were natural (i.e., momentum conserving) or anomalous (non-momentum conserving). 20 children at each age and 20 adults viewed videotapes of 8 collisions (4 natural, 4 anomalous) and 6 sequences of lifting events. Observers also viewed sequences of static images taken from these events. Observers at all grade levels were able to reliably judge relative weight in both collisions and lifting events, and could differentiate between natural and anomalous collisions. Performance was much poorer when static sequences of the events were viewed, especially for the young children. A consistent age trend was noted across tasks: adults performed better than second and fourth graders who, in turn, performed better than kindergartners. In addition, there was evidence that younger children were differentially aided when the kinematics of the event made the kinetics more pronounced.

Age Factors↗
PubMed1992

Conservation acquisition, maintenance, and generalization by mentally retarded children using equality-rule training.

To teach conservation to mildly retarded, preoperational preadolescents (9 to 12 years old), a number-representational system was used to mediate the invariance of quantity as part of "equality-rule" training. Before viewing a perceptually misleading configuration of either two equal quantities or two unequal quantities entailing the dimensions of number or length, participants learned that equality involved the assignment of two identical numbers and inequality the assignment of two different numbers. These numbers were then applied to the actual quantities and became the basis for rule statements that were rehearsed, memorized, and subject-generated each time the quantities were transformed into a new configuration. Following equality training, correct judgments and verbal justifications of conservation were high (M greater than or equal to 85%) during both immediate and delayed post-tests and for near-generalization (number and length) and far-generalization (weight, liquid substance, and solid substance) tasks. In contrast, the post-test levels of comparable participants given learning-set (LS) training, LS plus verbal-rule training (a combination of statements about identity, negation, and compensation), or no training at all were substantially and significantly lower. Equality training is of theoretical and practical interest because of its potential to teach a symbolic representational rule that directly and meaningfully articulates the quantitative properties of objects and counteracts the overreliance on task-specific and faulty perceptual cues inherent in the conservation task.

Child↗