Sensori-motor integration during stance: Time adaptation of control mechanisms on adding or removing vision

Sudden addition or removal of visual information can be particularly critical to balance control. The promptness of adaptation of stance control mechanisms is quantified by the latency at which body oscillation and postural muscle activity vary after a shift in visual condition. In the present study, volunteers stood on a force platform with feet parallel or in tandem. Shifts in visual condition were produced by electronic spectacles. Ground reaction force (center of foot pressure, CoP) and EMG of leg postural muscles were acquired, and latency of CoP and EMG changes estimated by t-tests on the averaged traces. Time-to-reach steady-state was estimated by means of an exponential model. On allowing or occluding vision, decrements and increments in CoP position and oscillation occurred within about 2 s. These were preceded by changes in muscle activity, regardless of visual-shift direction, foot position or front or rear leg in tandem. These time intervals were longer than simple reaction-time responses. The time course of recovery to steady-state was about 3 s, shorter for oscillation than position. The capacity of modifying balance control at very short intervals both during quiet standing and under more critical balance conditions speaks in favor of a necessary coupling between vision, postural reference, and postural muscle activity, and of the swiftness of this sensory reweighing process.     

Visual cues and perceived reachability

A rather consistent finding in studies of perceived (imagined) compared to actual movement in a reaching paradigm is the tendency to overestimate at midline. Explanations of such behavior have focused primarily on perceptions of postural constraints and the notion that individuals calibrate reachability in reference to multiple degrees of freedom, also known as the whole-body explanation. The present study examined the role of visual information in the form of binocular and monocular cues in perceived reachability. Right-handed participants judged the reachability of visual targets at midline with both eyes open, dominant eye occluded, and the non-dominant eye covered. Results indicated that participants were relatively accurate with condition responses not being significantly different in regard to total error. Analysis of the direction of error (mean bias) revealed effective accuracy across conditions with only a marginal distinction between monocular and binocular conditions. Therefore, within the task conditions of this experiment, it appears that binocular and monocular cues provide sufficient visual information for effective judgments of perceived reach at midline.     

Similarity and difference in the processing of same- and other-race faces as revealed by eye tracking in 4- to 9-month-olds

Fixation duration for same-race (i.e., Asian) and other-race (i.e., Caucasian) female faces by Asian infant participants between 4 and 9 months of age was investigated with an eye-tracking procedure. The age range tested corresponded with prior reports of processing differences between same- and other-race faces observed in behavioral looking time studies, with preference for same-race faces apparent at 3 months of age and recognition memory differences in favor of same-race faces emerging between 3 and 9 months of age. The eye-tracking results revealed both similarity and difference in infants’ processing of own- and other-race faces. There was no overall fixation time difference between same race and other race for the whole face stimuli. In addition, although fixation time was greater for the upper half of the face than for the lower half of the face and trended higher on the right side of the face than on the left side of the face, face race did not impact these effects. However, over the age range tested, there was a gradual decrement in fixation time on the internal features of other-race faces and a maintenance of fixation time on the internal features of same-race faces. Moreover, the decrement in fixation time for the internal features of other-race faces was most prominent on the nose. The findings suggest that (a) same-race preferences may be more readily evidenced in paired comparison testing formats, (b) the behavioral decline in recognition memory for other-race faces corresponds in timing with a decline in fixation on the internal features of other-race faces, and (c) the center of the face (i.e., the nose) is a differential region for processing same- versus other-race faces by Asian infants.     

Copying skills in relation to word reading and writing in Chinese children with and without dyslexia

Because Chinese character learning typically relies heavily on rote character copying, we tested independent copying skill in third- and fourth-grade Chinese children with and without dyslexia. In total, 21 Chinese third and fourth graders with dyslexia and 33 without dyslexia (matched on age, nonverbal IQ, and mother’s education level) were given tasks of copying unfamiliar print in Vietnamese, Korean, and Hebrew as well as tests of word reading and writing, morphological awareness, rapid automatized naming (RAN), and orthographic processing. All three copying tasks distinguished dyslexic children from nondyslexic children with moderate effect sizes (.67-.80). Zero-order correlations of the three copying tasks with dictation and reading ranged from .37 to .58. With age, Raven’s, group status, RAN, morphological awareness, and orthographic measures statistically controlled, the copying tasks uniquely explained 6% and 3% variance in word reading and dictation, respectively. Results suggest that copying skill itself may be useful in understanding the development and impairment of literacy skills in Chinese.     

How verbs can activate things: cross-language activation across word classes

The present study explored whether language-nonselective access in bilinguals occurs across word classes in a sentence context. Dutch–English bilinguals were auditorily presented with English (L2) sentences while looking at a visual world. The sentences contained interlingual homophones from distinct lexical categories (e.g., the English verb spoke, which overlaps phonologically with the Dutch noun for ghost, spook). Eye movement recordings showed that depictions of referents of the Dutch (L1) nouns attracted more visual attention than unrelated distractor pictures in sentences containing homophones. This finding shows that native language objects are activated during second language verb processing despite the structural information provided by the sentence context.     

The role of color information on object recognition: a review and meta-analysis

In this study, we systematically review the scientific literature on the effect of color on object recognition. Thirty-five independent experiments, comprising 1535 participants, were included in a meta-analysis. We found a moderate effect of color on object recognition (d = 0.28). Specific effects of moderator variables were analyzed and we found that color diagnosticity is the factor with the greatest moderator effect on the influence of color in object recognition; studies using color diagnostic objects showed a significant color effect (d = 0.43), whereas a marginal color effect was found in studies that used non-color diagnostic objects (d = 0.18). The present study did not permit the drawing of specific conclusions about the moderator effect of the object recognition task; while the meta-analytic review showed that color information improves object recognition mainly in studies using naming tasks (d = 0.36), the literature review revealed a large body of evidence showing positive effects of color information on object recognition in studies using a large variety of visual recognition tasks. We also found that color is important for the ability to recognize artifacts and natural objects, to recognize objects presented as types (line-drawings) or as tokens (photographs), and to recognize objects that are presented without surface details, such as texture or shadow. Taken together, the results of the meta-analysis strongly support the contention that color plays a role in object recognition. This suggests that the role of color should be taken into account in models of visual object recognition.     

Integration of disparity and velocity information for haptic and perceptual judgments of object depth

Do reach-to-grasp (prehension) movements require a metric representation of three-dimensional (3D) layouts and objects? We propose a model relying only on direct sensory information to account for the planning and execution of prehension movements in the absence of haptic feedback and when the hand is not visible. In the present investigation, we isolate relative motion and binocular disparity information from other depth cues and we study their efficacy for reach-to-grasp movements and visual judgments. We show that (i) the amplitude of the grasp increases when relative motion is added to binocular disparity information, even if depth from disparity information is already veridical, and (ii) similar distortions of derived depth are found for haptic tasks and perceptual judgments. With a quantitative test, we demonstrate that our results are consistent with the Intrinsic Constraint model and do not require 3D metric inferences (Domini, Caudek, & Tassinari, 2006). By contrast, the linear cue integration model (Landy, Maloney, Johnston, & Young, 1995) cannot explain the present results, even if the flatness cues are taken into account.     

The time course of face matching for featural and relational image manipulations

It was found recently that horizontal and vertical relationships of facial features are differently vulnerable to inversion (Goffaux & Rossion, 2007). When faces are upside down manipulations of vertical relations are difficult to detect, while only moderate performance deficits are found for manipulations of horizontal relations, or when features differ. We replicate the findings of Goffaux and Rossion, and record the temporal courses of face matching performance and the effects of inversion. For vertical relations and featural changes inversion effects arise immediately, starting with the first 50 ms of processing. For horizontal relations inversion effects are absent at brief timings, but arise later, after about 200 ms. The final magnitudes of inversion effects are different in all three conditions, reaching 23.4% for vertical displacement, 10.7% for feature replacement, and 5.8% for horizontal displacement. Our results underline the special status of horizontal in contrast to vertical feature relations, and indicate that local and global configural information is handled in parallel by specific routines, as proposed recently (Senunkova & Barton, 2008).     

The Shape Bias is Affected by Differing Similarity Among Objects

Previous research has demonstrated that visual properties of objects can affect shape-based categorization in a novel-name extension task; however, we still do not know how a relationship between visual properties of objects affects judgments in a novel-name extension task. We examined effects of increased visual similarity among the target and test objects in a shape bias task in young children and adults. Experiment 1 assessed college students with sets of objects whose similarity between target and test objects was either low or high similarity. Adults preferred shape when the similarity among objects was minimized. Experiment 2 tested 24-month olds in their use of the shape bias using the Intermodal Preferential Looking Paradigm. Children showed a shape bias only with items whose similarity to each other was low. These findings suggest that the visual properties of objects affect shape bias performance.     

Dissociating the effects of angular disparity and image similarity in mental rotation and object recognition

Performance is often impaired linearly with increasing angular disparity between two objects in tasks that measure mental rotation or object recognition. But increased angular disparity is often accompanied by changes in the similarity between views of an object, confounding the impact of the two factors in these tasks. We examined separately the effects of angular disparity and image similarity on handedness (to test mental rotation) and identity (to test object recognition) judgments with 3-D novel objects. When similarity was approximately equated, an effect of angular disparity was only found for handedness but not identity judgments. With a fixed angular disparity, performance was better for similar than dissimilar image pairs in both tasks, with a larger effect for identity than handedness judgments. Our results suggest that mental rotation involves mental transformation procedures that depend on angular disparity, but that object recognition is predominately dependent on the similarity of image features.