Lateral interception I: Operative optical variables, attunement, and calibration.

J. J. Gibson (1966, 1979) suggested that improvement in perception and action can be attributed in part to changes in which variable is attended to. Such reattunement has been demonstrated with observers making judgments in response to simulations. The present study sought attunement changes in the perception of real events and in visually guided action. In 3 experiments, adults judged the passing distance of or attempted to catch balls. Discrete measures and the predictions of a modified required velocity model (e.g., R. J. Bootsma, V. Fayt, F. T. J. M. Zaal, & M. Laurent, 1997) were used to reveal which variables were exploited. Participants differed from each other and, to some extent, changed in the optical variables used, in catching as well as judging. Nevertheless, the changes were much smaller than in previous simulation-judgment studies; calibration was also found to underlie the improvements in performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanical invariants are implicated in dynamic touch as a function of their salience in the stimulus flow.

The authors investigated the mechanical basis of length perception through dynamic touch using specially designed rods in which the various moments of mass distribution (mass, static moment, and rotational inertia) were varied independently. In a series of 4 experiments, exploration style and rod orientation were manipulated such that the relative salience of moments of mass distribution varied markedly. Results showed that perceived length was based on the most salient moments. The authors concluded that the notion of salience is crucial for understanding the implication of moments of mass distribution in length perception and that it should play a pivotal role in developing an encompassing theory of dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of fractality in perceptual learning: Exploration in dynamic touch.

Perceptual systems must learn to explore and to use the resulting information to hone performance. Optimal performance depends on using information available at many time scales, from the near instantaneous values of variables underlying perception (i.e., detection), to longer term information about appropriate scaling (i.e., calibration), to yet longer term information guiding variable use (i.e., attunement). Fractal fluctuations in explorations would entail fluctuation at all time scales, allowing perceptual systems a flexible way to detect information at all time scales. We tested whether perceptual learning in dynamic touch is related to the fractality of wielding behaviors. A reanalysis of wielding behaviors from Arzamarski, Isenhower, Kay, Turvey, and Michaels (2010) revealed that exploratory movements were fractal and that a fractal-scaling exponent predicts individual differences in haptic judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct learning in dynamic touch.

A dynamic touch paradigm in which participants judged the lengths of rods and pipes was used to test the D. M. Jacobs and C. F. Michaels (2007) theory of perceptual learning. The theory portrays perception as the exploitation of a locus on an information manifold and learning as continuous movement across that manifold to a new locus, as guided by information available in feedback. The information manifold was defined as a 1-dimensional space of inertial variables. To encourage maximal learning, a 2-step procedure was used in each of 2 experiments. Each step comprised a pretest to identify the starting locus on the information manifold, a practice phase in which feedback specifying the optimal locus was given, and a posttest in which the ending locus on the manifold was identified. In the 2nd step, a different feedback variable specified a different optimum. In both experiments, participants, who sometimes began at different loci, showed the predicted movement toward the optimum in each phase. Whereas previous applications of the theory posit the existence of information-for-learning without identifying a candidate variable, such a candidate is identified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spinors and selective dynamic touch.

Nonvisual perception of a hand-held object's length through wielding is known to be a function of the object's inertia tensor about a fixed rotation point in the wrist. The tensor is insufficient, however, to support perceptions of 2 different extents of an object in 2 different directions. The attitude spinor represents the tilt of the object's inertia ellipsoid relative to the hand in 2 oppositely oriented directions of rotation. Predictions about selective dynamic touch based on the spinor's 2-orientedness were confirmed in experiments in which participants wielded in 1 hand either (a) 2 rods, and attempted to perceive the length of one of them, or (b) 1 rod, and attempted to perceive the length of a part. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The inertia tensor versus static moment and mass in perceiving length and heaviness of hand-wielded rods.

In 2 experiments, participants haptically estimated length and heaviness of handheld rods while wielding without seeing them. The sets of rods had been constructed such that variation of static moment and the 1st eigenvalue of the inertia tensor (It) were separated. Consistent with previous findings, perceived rod length correlated strongly with It. However, multiple regressions on current data as well as data from previous studies showed a comparable strong correlation between perceived rod length and static moment plus mass. Contrary to previous findings, perceived heaviness correlated strongly with static moment and only weakly with the eigenvalues of the inertia tensor. These results suggest that the inertia tensor does not provide the sole foundation for a theory of dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the inertia tensor in perceiving object orientation by dynamic touch.

Ss wielded an occluded L-shaped rod and attempted to perceive the direction in which the rod was pointing with respect to the hand. The pattern of the rod's different resistances to rotation in different directions, quantified by the inertia tensor, changes systematically with the rod's orientation. Perception of orientation by wielding is possible if the tissue deformation consequences of the rod's inertia tensor are detectable. It was shown that perceived orientation was a linear function of actual orientation for both free and restricted wielding and for rods of different-size branches. The eigenvectors of the inertia tensor were implicated as the basis for this haptic perceptual capability. Results are discussed in reference to information–perception specificity and its implications for effortful or dynamic touch. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dynamics of disruption from altered auditory feedback: Further evidence for a dissociation of sequencing and timing.

Three experiments were designed to test whether perception and action are coordinated in a way that distinguishes sequencing from timing (Pfordresher, 2003). Each experiment incorporated a trial design in which altered auditory feedback (AAF) was presented for varying lengths of time and then withdrawn. Experiments 1 and 2 included AAF that resulted in action-effect asynchronies (delayed auditory feedback) during simple tapping (Experiment 1) and melody production (Experiment 2). Asynchronous AAF immediately slowed production; this effect then diminished rapidly after removal of AAF. By contrast, sequential alterations of feedback pitch during melody production (Experiment 3) had an effect that varied over successive presentations of AAF (by increasing error rates) that lasted after its withdrawal. The presence of auditory feedback after withdrawal of asynchronous AAF (Experiments 1 and 2) led to overcompensation of timing, whereas the presence of auditory feedback did not influence performance after withdrawal of AAF in Experiment 3. Based on these results, we suggest that asynchronous AAF perturbs the phase of an internal timekeeper, whereas alterations to feedback pitch over time degrade the internal representation of sequence structure. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Delayed retinal feedback of eye movements: A dynamic basis of perceptual disabilities.

Investigated temporal factors in vision in relation to the delay of the retinal feedback of ocular movements in eye tracking. A hybrid real-time computer system and dynamic programing methods were used to calibrate photoelectric eye-movement transducers in viewing visual targets, to yoke these targets to eye motion, to introduce feedback delays in eye-movement-retinal interaction, and to measure error in eye tracking. Results indicate that feedback delay affected the accuracy of both the compensatory and the pursuit tracking in a significant way, with a somewhat greater effect being found for pursuit movements. Since delay reduced smooth pursuit motions to saccadic reactions that varied in size with the delay interval, it is suggested that ocular dynamics and guidance in space perception are governed by time-specific neuron mechanisms of the central visual system. Findings negate classical theory of ocular dynamics and perception of direction by proving that directional guidance of the eyes is determined by directional specificity and temporal specificity of the feedback processes of pursuit and saccadic movements of the eyes and is not caused primarily by learned temporal association between visual and tactual sensory processes. It is concluded that major disabilities and distortions in vision, which are not reducible to traditionally defined optometric and ophthalmologic factors, may be produced by built-in developmental perturbations of ocular feedback timing. Findings emphasize dynamic optometric measurements in understanding common and elusive distortions of visual perception. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effortful touch with minimum movement: Revisited.

The ecological static moment-torque model proposed by C. Carello, P. Fitzpatrick, I. Domaniewicz, T. C. Chan, and M. T. Turvey (see record 1992-18467-001) does not uniquely explain the perception of rod length by static holding. Guided by a mechanical analysis of the gravitational forces and torques produced in the hand as it statically holds rods of different lengths and materials at different orientations, we offer 2 additional theoretical explanations, the force-torque and weight-percept models. Experiment 1 demonstrates that all 3 models predict perceived rod length with considerable success. Experiment 2 provides clear experimental support for the force-torque and weight-percept models over the static moment-torque model. Experiment 3 pits the former 2 models against each other. Current results favor the weight-percept model. Implications for theories of haptic weight perception and design of a new tactile sensor are also considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The perceptual experience of slope by foot and by finger.

Historically, the bodily senses have often been regarded as impeccable sources of spatial information and as being the teacher of vision. Here, the authors report that the haptic perception of slope by means of the foot is greatly exaggerated. The exaggeration is present in verbal as well as proprioceptive judgments. It is shown that this misperception of pedal slope is not caused by calibration to the well-established visual misperception of slope because it is present in congenitally blind individuals as well. The pedal misperception of slope is contrasted with the perception of slope by dynamic touch with a finger in a force-feedback device. Although slopes feel slightly exaggerated even when explored by finger, they tend to show much less exaggeration than when equivalent slopes are stood on. The results are discussed in terms of a theory of coding efficiency. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cognitive control factors in speech perception at 11 months.

The development of speech perception during the 1st year reflects increasing attunement to native language features, but the mechanisms underlying this development are not completely understood. One previous study linked reductions in nonnative speech discrimination to performance on nonlinguistic tasks, whereas other studies have shown associations between speech perception and vocabulary growth. The present study examined relationships among these abilities in 11-month-old infants using a conditioned head-turn test of native and nonnative speech sound discrimination, nonlinguistic object-retrieval tasks requiring attention and inhibitory control, and the MacArthur-Bates Communicative Development Inventory (L. Fenson et al., 1993). Native speech discrimination was positively linked to receptive vocabulary size but not to the cognitive control tasks, whereas nonnative speech discrimination was negatively linked to cognitive control scores but not to vocabulary size. Speech discrimination, vocabulary size, and cognitive control scores were not associated with more general cognitive measures. These results suggest specific relationships between domain-general inhibitory control processes and the ability to ignore variation in speech that is irrelevant to the native language and between the development of native language speech perception and vocabulary. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inertia tensor and weight-percept models of length perception by static holding.

S. J. Lederman, S. R. Ganeshan, and R. E. Ellis (1996) reported an experiment demonstrating that for occluded rods of equal mass and length but different diameters length perception by static holding was larger for rods of smaller diameter. They concluded that participants inferred length from illusory weight percepts. However, rods of equal mass and length that differ in diameter also differ in the eigenvalues of their respective inertia tensors. In the present experiments, the authors manipulated the diameters (Experiment 1) and the inertial eigenvalues (Experiments 4 and 5) of statically held objects. As has been shown with wielded objects, perceived length was a function of the eigenvalues. Additional experiments failed to confirm the expectation from the weight-percept model that perceived length maps to the estimated weight (Experiments 2 and 3). Physical quantities, not psychological quantities, seem to explain length perception by static holding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modification of ceftibuten transport by changes in lipid fluidity caused by fatty acid glycerol esters

The authors previously observed that schizophrenic patients generated fewer fixations of < or = 50.1 ms in response to faces than did a clinical control group. This study examined whether deficits in short-duration eye movements were related to patients' problems in gestalt perception of faces. Faces were presented in upright and inverted orientations to examine the effects of distorting facial gestalts on eye movements. Normal subjects generated more saccades of < or = 50.1 ms to upright than to inverted faces. Patients' saccades of < or = 50.1 ms did not differ between orientations. Patterns of fixations and of saccades > 50.1 ms did not differ between groups. The results may indicate deficits in these patients in search strategies that underlie perception of facial gestalts.     

Establishing minimum performance standards, calibration intervals, and optimal exposure values for a whole breast digital mammography unit

Methods are developed to establish minimum performance standards, calibration intervals, and criteria for exposure control for a whole breast digital mammography system. A prototype phantom was designed, and an automatic method programmed, to analyze CNR, resolution, and dynamic range between CCD components in the image receptor and over time. The phantom was imaged over a 5 month period and the results are analyzed to predict future performance. White field recalibration was analyzed by subtracting white fields obtained at different intervals. Exposure effects were compared by imaging the prototype phantom at different kVp, filtration (Mo vs Rh) and mAs. Calcification detection tests showed that phantom images, obtained at 28 kVp with a Mo/Mo anode/filter and low mAs technique, often could not depict Al2O3 specks 0.24 mm in diameter, while a 28 kVp Mo/Rh, higher mAs technique usually could. Stability of the system tested suggests that monthly phantom imaging may suffice. Differences in CCD performance are greater (12%) than differences in a single CCD over time (6%). White field recalibration is needed weekly because of pixel variations in sensitivity which occur if longer intervals between recalibration occur. When mean glandular dose is matched, Rh filtration gives better phantom performance at 28 kVp than Mo filtration at 26 kVp and is recommended for clinical exposures. An aluminum step wedge shows markedly increased dynamic range when exit exposure is increased by using a higher energy spectrum beam. Phantoms for digital mammography units should cover the entire image receptor, should test intersections between components of the receptor, and should be automatically analyzed.     

The necessity of a perception–action approach to definite distance perception: Monocular distance perception to guide reaching.

In this investigation of monocular perception of egocentric distance, the authors advocate the necessity of a perception–action approach because calibration is intrinsic to definite distance perception. A helmet-mounted camera and display were used to isolate optic flow generated by participants' head movements toward a target, and participants' reaches to place a stylus either in a target hole (Experiments 1, 2, and 4) or aligned under a target surface (Experiment 3) were analyzed. Conclusions are that binocular distance perception is accurate, monocular distance perception yields compression that is not eliminated by feedback, but feedback is used to eliminate underestimation generated by restriction of the size of the visual field. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Scaling of Information to Action in Visually Guided Braking.

Braking to avoid a collision can be controlled by keeping the deceleration required to stop (i.e., ideal deceleration) in the "safe" region below maximum deceleration, but maximum deceleration is not optically specified and can vary as conditions change. When brake strength was manipulated between participants using a simulated braking task, the ratio of ideal to maximum deceleration at brake onset was invariant across groups, suggesting that calibration involves scaling information about ideal deceleration in intrinsic units of maximum deceleration. Evidence of rapid recalibration was found when brake strength was manipulated within participants, and the presence of external forces that affect brake dynamics resulted in biases in performance. Discussion focuses on the role of calibration, internal models, and affordance perception in visually guided action. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Processing reduced word-forms in speech perception using probabilistic knowledge about speech production.

Two experiments examined how Dutch listeners deal with the effects of connected-speech processes, specifically those arising from word-final /t/ reduction (e.g., whether Dutch [tas] is tas, bag, or a reduced-/t/ version of tast, touch). Eye movements of Dutch participants were tracked as they looked at arrays containing 4 printed words, each associated with a geometrical shape. Minimal pairs (e.g., tas/tast) were either both above (boven) or both next to (naast) different shapes. Spoken instructions (e.g., "Klik op het woordje tas boven de ster,' [Click on the word bag above the star]) thus became unambiguous only on their final words. Prior to disambiguation, listeners' fixations were drawn to /t/-final words more when boven than when naast followed the ambiguous sequences. This behavior reflects Dutch speech-production data: /t/ is reduced more before /b/ than before /n/. We thus argue that probabilistic knowledge about the effect of following context in speech production is used prelexically in perception to help resolve lexical ambiguities caused by continuous-speech processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lateral difference in the reproduction of arm positioning movement: an examination of the hypothesis on the levels of psychological processes

The purpose of this study was to determine whether the hypothesis on the levels of psychological processes (Hatta, 1977, 1978) accounts for lateral differences in arm positioning movement (a spatial localization task). Fifteen right-handed male subjects were asked to perform a constrained criterion movement, 12 cm in length, with the left or right arm. Then, after a 10-sec retention interval, they were asked to perform the movement with the same arm, estimating lengths of 6, 12 or 24 cm. Different levels of psychological processes were assumed to be involved in estimating these various movement lengths--half, the same, or double that of the original. All possible combinations of the arm (left/right) and three movement length were tested. The CE scores were lower (more accurate) for the left arm (half; 1.5 +/- 8.1 mm, same; 4.3 +/- 6.2mm, double; 5.9 +/- 20.3 mm) than those for the right arm (half; 5.9 +/- 7.6 mm, same; 10.6 +/- 10.6 mm, double; 11.8 +/- 23.6 mm) in all conditions, indicating a lateral difference (the right hemisphere dominance) in arm positioning tasks. This typical lateral difference, which displayed no significant difference among conditions, is supposed to be mediated by complex or high-level psychological processes. These psychological processes are required by the subjects in the estimation of the various movement lengths. This study suggests that the level of psychological processes is a crucial factor in the manifestation of lateral differences in the performance of arm positioning movements.