Three-dimensional baselines for perceived self-motion during acceleration and deceleration in a centrifuge

Three-dimensional motion trajectories were computed, representing the motions that would be perceived by a perfect processor of acceleration information during the acceleration and deceleration stages of a centrifuge run. These motions serve as "baselines" for perceived self-motion in a centrifuge, and depend on the initial perception of orientation and velocity immediately preceding the acceleration and immediately preceding the deceleration. The baselines show that a perfect processor of acceleration information perceives self-motion during centrifuge deceleration significantly differently from self-motion during centrifuge acceleration, despite the fact that the angular accelerations have equal magnitude (with opposite direction). At the same time, the baselines can be compared with subjects' reported perceptions to highlight limitations of the nervous system; limitations and peculiarities of the nervous system are identified as deviations from a baseline. As a result, peculiarities of the nervous system are held responsible for any perception of pitch or roll angular velocity or change in tilt of the body-horizontal plane of motion during the centrifuge run. On the other hand, baselines explain perception of tilt position during deceleration, linear velocity, possible lack of significant linear velocity during deceleration, and yaw angular velocity, including on-axis angular velocity during centrifuge deceleration. The results lead to several experimental questions.     

Perceiving scene layout through an aperture during visually simulated self-motion.

Tested scene perception during depicted self-movement. In Exp 1, viewers reproduced angular scene configurations, revealed over time by camera motions in depth. Viewers used visible flow to update off-screen locations of landmarks that had been drawn from view and thereby perceived scenes in depth beyond the display's boundaries. Exps 2 and 3 tested whether offscreen space is perceived as a function of depicted velocity and time and whether information from prior views is used. Viewers predicted when lateral movement would reveal a peripheral landmark whose location was shown in a prior panoramic view. Accurate responses, observed under certain conditions, would result if viewers perceived space according to S?=?∫ V dt (D. Algom and L. Cohen-Raz, 1984, 1987; R. Jagacinski et al, 1983). When required to picture wide spans in space yet to emerge, however, viewers responded as if these spans were compressed. The theoretical implications of the ability to retrieve, transform, and apply information after a discontinuous transition from a prior view are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Judgments about the time to contact between two objects during simulated self-motion.

Estimates of the time to contact (TTC) between 2 objects with simulations of no self-motion (SM) or SM at various speeds and directions were measured. In some cases, SM can affect TTC estimates, but in other cases, observers may compensate for effects of SM on optic flow. Under some conditions, estimates were comparable for no SM and forward or backward SM, even when SM nullified the constriction of the optical gap between the 2 objects. Furthermore, background texture can affect TTC estimates. Results suggest that observers can judge the TTC between 2 objects during SM but performance obtained during stationary viewing may not generalize to SM. Factors other than optical TTC information must be considered in models of perceived collision. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Emotional expression modulates perceived gaze direction.

Gaze perception is an important social skill, as it portrays information about what another person is attending to. Gaze direction has been shown to affect interpretation of emotional expression. Here the authors investigate whether the emotional facial expression has a reciprocal influence on interpretation of gaze direction. In a forced-choice yes-no task, participants were asked to judge whether three faces expressing different emotions (anger, fear, happiness, and neutral) in different viewing angles were looking at them or not. Happy faces were more likely to be judged as looking at the observer than were angry, fearful, or neutral faces. Angry faces were more often judged as looking at the observer than were fearful and neutral expressions. These findings are discussed on the background of approach and avoidance orientation of emotions and of the self-referential positivity bias. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heading judgments during active and passive self-motion

Previous studies have generally considered heading perception to be a visual task. However, since judgments of heading direction are required only during self-motion, there are several other relevant senses which could provide supplementary and, in some cases, necessary information to make accurate and precise judgments of the direction of self-motion. We assessed the contributions of several of these senses using tasks chosen to reflect the reference system used by each sensory modality. Head-pointing and rod-pointing tasks were performed in which subjects aligned either the head or an unseen pointer with the direction of motion during whole body linear motion. Passive visual and vestibular stimulation was generated by accelerating subjects at sub- or supravestibular thresholds down a linear track. The motor-kinesthetic system was stimulated by having subjects actively walk along the track. A helmet-mounted optical system, fixed either on the cart used to provide passive visual or vestibular information or on the walker used in the active walking conditions, provided a stereoscopic display of an optical flow field. Subjects could be positioned at any orientation relative to the heading, and heading judgments were obtained using unimodal visual, vestibular, or walking cues, or combined visual-vestibular and visual-walking cues. Vision alone resulted in reasonably precise and accurate head-pointing judgments (0.3 degrees constant errors, 2.9 degrees variable errors), but not rod-pointing judgments (3.5 degrees constant errors, 5.9 degrees variable errors). Concordant visual-walking stimulation slightly decreased the variable errors and reduced constant pointing errors to close to zero, while head-pointing errors were unaffected.     

Pictorial and motion-based depth information during active control of self-motion: Size-arrival effects on collision avoidance.

With computer simulations of self-motion, Ss controlled their altitude as they approached a floating object and, after getting as close as possible to the object, tried to "jump" over it without collision. Ss jumped significantly later for small objects, compared with larger objects that were approached from equal distances at equal speeds and were positioned at equal clearance heights. This occurred even when accretion-deletion information was present and when object width and length were varied independently. Results were consistent with studies (e.g., P. R. Delucia, see record 1992-00230-001) in which Ss judged a large, far-approaching object to hit the viewpoint before a small, near object that would have arrived sooner. Results suggest that pictorial information such as relative size contributes to active collision-avoidance tasks and must be considered in models of perceived distance and time-to-arrival. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sources of optical information useful for perception of speed of rectilinear self-motion.

Magnitude judgments of the speed of self-motion were examined. The principal independent variables were edge rate, global optical flow rate, and the type of texture (grid or dot). Results indicated that edge rate and global optical flow rate had additive effects on magnitude judgments, with edge rate accounting for a larger portion of the variance. Effects were independent of texture type. Secondary variables examined were viewing condition and task load. Attempts were made to control the availability of flatness cues. Evidence indicates that the effectiveness of global optical flow rate varied with the control of flatness cues. A secondary running auditory Sternberg task (S. Sternberg, 1969) was used to prevent edge counting; the presence of this task did not reduce the effect of edge rate. These results replicate and extend previous work by D. H. Owen and colleagues (1984 and 1987). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of gaze aversion as disengagement from visual information.

Older children, but not younger children, were found to look away more from the face of an interlocutor when answering difficult as opposed to easy questions. Similar results were found in earlier work with adults, who often avert their gaze during cognitively difficult tasks (A. M. Glenberg, J. L. Schroeder, & D. A. Robertson, 1998). Twenty-five 8-year-olds and 26 5-year-olds answered verbal reasoning and arithmetic questions of varying difficulty. The older children increased gaze aversion from the face of the adult questioner in response to both difficult verbal reasoning questions and difficult arithmetic questions. In contrast, younger children (5-year-olds) responded less consistently to cognitive difficulty. It is concluded that adultlike patterns of gaze aversion in response to cognitive difficulty are certainly acquired by 8 years of age. The implications of appropriate gaze aversion for children's management of cognitive processing resources are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Source credibility and perceived expertness of testimony in a simulated child-custody case.

Used a 2?×?2?×?4?×?2 completely randomized, between-S factorial design in a simulated child custody hearing to evaluate the effects of the sex of the S, sex of the witness, experience level of the witness, and witness status (psychiatrist, clinical psychologist, social worker, neighbor) on perceived expertness. 192 male and 192 female undergraduates listened to an audiotape of simulated testimony in a child custody case and subsequently completed a semantic-differential questionnaire embedded with items to evaluate perceived expertise of a source. Ss were assigned to different groups based on the version of testimony heard. Results indicate that experience level and witness status significantly influenced Ss' evaluations of witness expertise. Female Ss rated all witnesses higher in expertness, and there was a trend that suggested female witnesses may be judged as more expert. Results are discussed in reference to implicit notions that people may have of mental health professionals involved in court proceedings and the possible ramifications of the involvement of such professionals in legal matters. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Crystal rotations during the rolling of large-grained aluminium sheet

The formation of a rolling texture has been studied by following the crystal orientations of 19 grains in two sheets of large-grained aluminium rolled to thickness reductions up to 80%. The experimental results for the individual grains are compared with the theoretical lattice rotations calculated for different simple grain deformation modes, namely: fully constrained (FC) plane strain compression, and partially constrained plane strain compression in which one or both in-plane shears are unprescribed. The calculations are performed using the classical Bishop-Hill method for FC deformations and the relaxed constraints (RC) method for partially prescribed grain deformations, together with the recent Renouard-Wintenberger minimum 2nd order work hypothesis. The lattice rotations of almost half the grains are in good quantitative agreement with the RC model. Some grains rotate according to the FC (Taylor) model along the minimum 2nd order work path. The rotations of the remaining grains are qualitatively close to the rather similar predictions of both models. The orientation dependence of the deformation mode of the grains can be correlated with the respective plastic work terms for the FC and RC models.     

Depth perception during diplopia is direct

Although depth is experienced with targets at large disparities when they are seen as double or diplopic, whether that depth is as direct as with fused targets has been a matter of considerable uncertainty. Researchers have often claimed that judgments of the depth of diplopic targets during simple near/far tasks rely upon indirect associations with eye-muscle proprioception or a copy of the vergence drive signal. We designed a four-alternative task that could not be performed without a direct appreciation of depth. Observers judged the depths of each of two Gabor stereo pairs presented simultaneously. Disparities were always above each observer's measured diplopia threshold. The signs of the disparities were varied independently and observers reported the perceived depth near and far for each target. Our results demonstrate conclusively that depth during diplopia requires neither proprioception nor an efferent copy but is direct.     

Depth perception as a function of motion parallax and absolute-distance information.

Conducted 3 experiments with 12 observers from a university community to determine whether the visual system calibrates motion parallax according to absolute-distance information in processing depth and to map the range of depth perception as a function of distance and motion parallax. The parallax was created by yoking the relative movement of random dots displayed on a CRT to the movements of the head. In Exp I, at viewing distances of 40 and 80 cm, Ss reported the apparent depth produced by motion parallax equivalent to a binocular disparity of 0.47°. The mean apparent depth at 80 cm was 2.6 times larger than at 40 cm. In Exp II, again at viewing distances of 40 and 80 cm, Ss adjusted the extent of parallax so that the apparent depth was 7.0 cm. The mean extent of parallax at 80 cm was 31% of that at 40 cm. These findings show that the visual system does calibrate motion parallax according to absolute-distance information in processing depth. In Exp III, distances ranged from 40 to 320 cm, and a wide range of parallax was used. As distance and parallax increased, the perception of a rigid 3-dimensional surface was accompanied by rocking motion; perception of depth was replaced by perception of motion in some trials at 320 cm. Moreover, the mean apparent depths were proportional to the viewing distance at 40 and 80 cm but not at 160 and 320 cm. (25 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Estimating heading during real and simulated eye movements

The ability to judge heading during tracking eye movements has recently been examined by several investigators. To assess the use of retinal-image and extra-retinal information in this task, the previous work has compared heading judgments with executed as opposed to simulated eye movements. For eye movement velocities greater than 1 deg/sec, observers seem to require the eye-velocity information provided by extra-retinal signals that accompany tracking eye movements. When those signals are not provided, such as with simulated eye movements, observers perceive their self-motion as curvilinear translation rather than the linear translation plus eye rotation being presented. The interpretation of the previous results is complicated, however, by the fact that the simulated eye movement condition may have created a conflict between two possible estimates of the heading: one based on extra-retinal solutions and the other based on retina-image solutions. In four experiments, we minimized this potential conflict by having observers judge heading in the presence of rotations consisting of mixtures of executed and simulated eye movements. The results showed that the heading is estimated more accurately when rotational flow is created by executed eye movements alone. In addition, the magnitude of errors in heading estimates is essentially proportional to the amount of rotational flow created by a simulated eye rotation (independent of the total magnitude of the rotational flow). The fact that error magnitude is proportional to the amount of simulated rotation suggests that the visual system attributes rotational flow unaccompanied by an eye movement to a displacement of the direction of translation in the direction of the simulated eye rotation.     

Mandibular forces during simulated tooth clenching

Differential, functional loading of the mandibular condyles has been suggested by several human morphologic studies and by animal strain experiments. To describe articular loading and the simultaneous forces on the dental arch, static bites on a three-dimensional finite element model of the human mandible were simulated. Five clenching tasks were modeled: in the intercuspal position; during left lateral group effort; during left lateral group effort with balancing contact; during incisal clenching; and during right molar clenching. The model's predictions confirmed that the human mandibular condyles are load-bearing, with greater force magnitudes being transmitted bilaterally during intercuspal and incisal clenching, as well as through the balancing-side articulation during unilateral biting. Differential condylar loading depended on the clenching task. Whereas higher forces were found on the lateral and lateroposterior regions of the condyles during intercuspal clenching, the model predicted higher loads on the medial condylar regions during incisal clenching. The inclusion of a balancing-side occlusal contact seemed to decrease the forces on the balancing-side condyle. Whereas the predicted occlusal reaction forces confirmed the lever action of the mandible, the simulated force gradients along the tooth row suggest a complex bending behavior of the jaw.     

Fixation disparity, accommodation, dark vergence and dark focus during inclined gaze

The colony-forming unit-granulocyte-macrophage (CFU-GM) assay, an essential test in evaluation of the quality of autologous grafts of hematopoietic stem cells, has yet to be standardized. With this aim in view, we carried out a multicenter study of five commercially available culture kits for CFU-GM evaluation. Four kits were methylcellulose-based (H4431, H4434, H4435, StemBio1d) and one was collagen-based (EasyClone-Multi). Using fresh and frozen samples of PBSC grafts, we compared CFU-GM and burst-forming unit-erythrocytes (BFU-E) growth using the EasyClone kit to each of the methylcellulose kits. BFU-E and CFU-GM clonogenicity of both fresh and frozen PBSC was clearly inferior with the H4431 kit, which provides conditioned medium only. CFU-GM numbers obtained with fresh and frozen PBSC samples were significantly higher with the EasyClone kit than with the H4434 and StemBio kits. BFU-E numbers were also higher with the EasyClone kit, but only when colonies were scored after May-Grünwald-Giemsa (MGG) staining. Finally, although the H4435 kit provides higher doses of recombinant cytokines than the EasyClone kit, CFU-GM and BFU-E numbers obtained for fresh or frozen PBSC with both kits were similar. In addition, CFU-GM and BFU-E numbers correlated well with CD34+ cell numbers for all five kits for both fresh and frozen PBSC. In summary, our study shows that the EasyClone-Multi and H4435 kits provide the best CFU-GM growth. The collagen-based EasyClone kit has the additional advantage of allowing gel staining and storage, which facilitates colony identification and, more importantly, makes gel exchange possible for standardization of the CFU-GM assay.     

The impact of stereotype-incongruent information on perceived group variability and stereotype change.

[Correction Notice: An erratum for this article was reported in Vol 78(4) of Journal of Personality and Social Psychology (see record 2007-17406-001). In this article, Table 3 (p. 987) contained an error. The row "Number of subgroups" was inadvertently omitted. The corrected table appears in this erratum.] Three experiments showed increases in the perceived variability of social groups after perceivers received stereotype-incongruent information about group members. In Experiment 1, participants generated flatter distributions after exposure to incongruent information, compared with equally deviant congruent information, in the form of typical verbal materials. Experiment 2 indicated similar changes in dispersion after the presentation of numeric information about a single group member. In Experiment 3, the authors manipulated cognitive load at encoding or at the time group judgments were requested. Under conditions of cognitive constraint, stereotype-incongruent information ceased to promote more dispersed group representations. These results are consistent with the idea that incongruent information triggers more deliberative and comprehensive retrieval and generation of exemplars. The authors discuss the implications of these findings for stereotype change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of distance information and range on two indices of visually perceived distance

Subjects made verbal reports of the perceived distance of near visual targets and indicated their distances by pointing at them with an unseen hand. The targets were presented under three stimulus conditions: monocular, binocular, and multicue. Two ranges of target distance were studied in separate experiments: 11-39 cm and 21-33 cm. When reciprocals of both response distance and target distance were plotted, all functions were approximately linear. The verbal and manual responses (distance indices) differed greatly, but were found to be related by a constant transform. The range of target distances had no effect on either index. The standard deviation of the manual response was about half that of the verbal response. Stimulus condition had a large effect, with the multicue condition producing the greatest change in indicated distance. and the monocular condition the least. The results are discussed with reference to the definition of perceived distance, and hypothesis concerning the integration of distance information.     

Perception of self-motion: Psychophysical and computational approaches.

Visually induced perception of self-motion has been studied from 2 perspectives—one concerned with psychophysical relations between the visual stimulus and the perception of self-motion and a 2nd concerned with computational relations between changing 2-dimensional projections and observer motion in a 3-dimensional environment. Results from these 2 perspectives are analyzed in terms of the occurrence of perceived rotation and translation, the perceived direction of self-motion, eye movements, focal/ambient theory, and optic flow. The lack of interaction between the different approaches is noted, and it is argued that further research, integrating these 2 approaches, is needed for a more complete understanding of the distinctions between optical transformations that result in perceived object motion and those that result in perceived self-motion. (75 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's use of triadic eye gaze information for "mind reading."

Five experiments examined children's use of eye gaze information for "mind-reading" purposes, specifically, for inferring another person's desire. When presented with static displays in the first 3 experiments, only by 4 years of age did children use another person's eye direction to infer desires, although younger children could identify the person's focus of attention. Further, 3-year-olds were capable of inferring desire from other nonverbal cues, such as pointing (Experiment 3). When eye gaze was presented dynamically with several other scaffolding cues (Experiment 4), 2- and 3-year-olds successfully used eye gaze for desire inference. Scaffolding cues were removed in Experiment 5, and 2- and 3-year-olds still performed above chance in using eye gaze. Results suggest that 2-year-olds are capable of using eye gaze alone to infer about another's desire. The authors propose that the acquisition of the ability to use attentional cues to infer another's mental state may involve both an association process and a differentiation process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)