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PubMed1995

One line decreases the visibility of a simultaneous identical distant second line.

A top line decreased the visibility of a simultaneous, identical, distant bottom line. This context-produced decrease in visibility (DV) occurred when the bottom line was masked by flanking lines and hence was less visible than the top line. It continued when the top line was three times as far from the bottom line. It disappeared without the mask. There was a hint of an opposing context-produced increase in visibility (IV) when the lines were close together. The DV is not accounted for by numerous extant phenomena and theories. It means that the top line decreased the similarity in visibility between it and the bottom line, a contrast effect for visibility, rather than for a typical attribute. Contrast does not occur between two attributes that are perceptually equal. Therefore, the reason why two distant equally visible objects fail to result in a DV may be that their equal visibility precludes the occurrence of contrast. This DV-as-contrast theory is consistent with evidence that two groups (phenomenal wholes) are associated with both contrast and DVs, and thus also with evidence that one group is associated with both assimilation and IVs.

Attention↗
PubMed1995

Cross-modality matches of finger span and line length.

Perceived finger span--the perceived spatial separation between the tip of the thumb and the tip of the index finger--was measured by using cross-modal matching to line length. In the first experiment, subjects adjusted finger span to match the length of line segments presented on a video monitor, and conversely, with both hands. Subjects also made estimates of finger span in physical units ("dead reckoning"). Finger spans were measured by using infrared LEDs mounted on the tip of the thumb and the finger tip, so the hand made no contact with any object during the experiment. Unlike in previous studies, the results suggest that perceived finger span is proportional to line length and slightly shorter than the actual span, provided that corrections are made for regression bias. The effect of finger contact was assessed in a second experiment by matching line length both to free span and to spans constrained by the pinching of blocks in the same session. The matching function when subjects were pinching blocks was accelerating, consistent with previous reports. In contrast, matched line length was a decelerating function of free span. The exponent of the free span matching function in the second experiment was slightly smaller than in the first experiment, probably due to uncorrected matching biases in the second experiment.

Adult↗
PubMed1996

Spatial distribution of visual attention: perceptual sensitivity and response latency.

Studies of the spatial distribution of visual attention have shown that attentional facilitation monotonically decreases in a graded fashion with increasing distance from an attended location. However, reaction time (RT) measures have typically shown broader gradients than have signal detection (SD) measures of perceptual sensitivity. It is not clear whether these differences have arisen because the stages of information processing indexed by RT measures are different from those indexed by SD measures, or whether these differences are due to methodological confounds in the SD studies. In the present set of experiments, the spatial distribution of attention was studied by using a luminance detection task in an endogenous cuing paradigm that was designed to permit accurate calculations of SD and RT measures for targets at cued and uncued locations. Subjects made target-present/absent decisions at one of six possible cued or uncued upper visual hemifield locations on each trial. The results from three experiments suggest that the differences between broad and focal attentional distributions are not the result of different stages of information processing indexed by RT measures as opposed to SD measures. Rather, the differing distributions appear to reflect variations in attentional allocation strategies induced by the perceptual requirements typical of RT paradigms as opposed to SD paradigms. These findings support numerous prior studies showing that spatial attention affects perceptual sensitivity and that the strategic allocation of attention is a highly flexible process.

Adolescent↗
PubMed1988

[The double-nail illusion revisited: commonality with the wallpaper phenomenon].

The double-nail illusion occurs when the images of two nails located at different distances from the observer fall on the corresponding retinal points, giving rise to the impression that the two nails are placed side by side at an equal distance from him. Experiment 1 showed that when two stimuli located on the mid-sagittal plane and at different distances were viewed in such a way that their images fall on the corresponding points, the perceived distance of the stimuli corresponded to the convergence distance. In Experiment 2, the convergence distance was changed gradually to get the measure of the distances at which the double-nail illusion appeared or disappeared. The results indicated the same kind of hysteresis as that previously observed in the 'dynamic' wallpaper phenomenon. Experiment 3 demonstrated the "double" wallpaper illusion, in which two wallpaper stimuli located in two different frontal-parallel planes appeared in a plane between the two and parallel to them. It showed moreover that the perceived distance of the wallpaper stimuli corresponded to the perceived distance obtained in the case of the double-nail illusion. The results of the three experiments indicated the commonality of the double-nail illusion with the wallpaper phenomenon and suggested that they share the same underlying perceptual processes. The principles of egocentric visual direction and distance were discussed with respect to the results.

Adult↗
PubMed1998

[The effect of interviewer distance on eyeblinks and heart rates of interviewee].

The purpose of the present study was to investigate the effect of interviewer distance on interviewee eyeblinks and heart rates. The interviewer was a 22 year-old woman, and 21 undergraduates, eight men and 13 women, participated in the study as interviewees. Interviews were conducted under three distance conditions: close (0.8 m), middle (2.0 m), and distant (4.0 m). A polygraph recorded the interviewee's eyeblinks and heart rates during the interview. After the interview, the interviewee rated his/her own psychological state during the interview, and reported impressions of the interviewer. Results showed that interviewees blinked more frequently in the close condition than the other conditions. No significant effect was found on heart rate. Interviewees rated their psychological state as more negative in the close condition, but impression to the interviewer remained the same across the conditions. These results indicated that eyeblink is a useful physiological index of effects that interpersonal situations have.

Adult↗
PubMed2001

[Effects of gender and physical distance with an old friend on same-sex friendship].

This study examined the differences between interpersonal relationship of same-sex old friends (OF) and that of new friends (NF). It also investigated the effects of physical distance with an old friend and gender on the friendship. Respondents were 208 undergraduates, 86 men and 122 women, who chose one of most intimate person each from same-sex friends they had made before and after they entered a university, and answered questions to describe their relationship. Results showed that relationship satisfaction and tired feeling were higher for OF than NF. Spending time together and talking over telephone were more frequent for NF than OF, but for each occasion together or over telephone, OF spent longer time than NF. OF expected more self-disclosure between them than NF. Gender differences in friendship expectation were similar to previous findings (Wada, 1993, 1996). Furthermore, gender and physical distance both influenced the frequencies of OF spending time together and over telephone. These findings are discussed in terms of gender differences in friendship.

Adult↗
PubMed1976

Infant visual acuity as a function of viewing distance.

Dynamic retinoscopy has suggested that near vision may be more acute than far vision during early infancy. To test this, acuity thresholds were determined by presenting square wave gratings in a preference paradigm to 1- and 2-month-old human infants at 4 viewing distances. Gratings were paired with unpatterned fields; direction of first fixation was the dependent measure. Infants exhibited the same acuity at each of the distances at which gratings were presented. The results were interpreted as compatible with the fact that considerable optical defocusing does not seriously affect a visual system, such as the infant's, that is sensitive only to low spatial frequencies.

Accommodation, Ocular↗
PubMed1976

[First communication: normal values of horizontal breadth fusion for distance vision (author's transl)].

Binocular fusion at 33 cm needs a fusion force of about 18 pdpt (delta) in convergence. In serial investigations on more than 2500 patients with normal binocular vision the fusion force is found to be limited to: in convergence max. 15.8 +/- 7.4 delta, in spontaneous convergence +18.8 +/- 5.3 delta, in divergence-5.6 +/- 2.3 delta. That seems to demonstrate, that in normal binocular vision with normal fusion force and without any subjective trouble the visual point must not be exactly in the foveolae of both eyes.

Adolescent↗
PubMed1976

Instrument myopia--microscopy.

Looking through optical instruments stimulates the eye to accommodate more than would be necessary for naked eye viewing; this increased near power is called instrument myopia. The amount (up to -5 diopters) varies with the observer and the conditions of viewing. Using microscopes produces -1.5 to -2 diopters of instrument myopia. More instrument myopia is found with low-power magnification, inexperienced users, and when focusing form minus blur to sharp image. Physiologically, the instrument myopia appears to be associated with an accommodative equilibrium position and, psychologically, with a sensing of proximity.

Accommodation, Ocular↗
PubMed1999

A 25-year prospective study of visual acuity in the Japan Air Self Defense Force personnel.

BACKGROUND: In the Japan Air Self Defense Force (JASDF), new vision standards for student pilots allow lower uncorrected monocular acuity (from 1.0 to 0.8). In flight environments, where the use of corrective lenses may present problems, the risk of decreasing visual acuity in pilots who should wear corrective lenses must be defined. METHODS: We conducted a 25-yr prospective study of visual acuity with regard to distance vision in 752 JASDF nonaviation personnel followed from ages 20 to 45. The test subjects were divided into four groups according to their right monocular visual acuity at entry: > or =1.0, between 0.9 and 0.7, between 0.6 and 0.2, and <0.2. RESULTS: At entry, 94.1% of all subjects had visual acuity > or =0.7. The proportion of subjects who required corrective lenses for distance increased with age from 15.8% to 37.1%. After 25-yr, 30.2% of subjects with visual acuity > or =1.0 at entry and 62.7% of subjects with visual acuity between 0.9 and 0.7 at entry required corrective lenses. CONCLUSIONS: Over 25 yr, the population with the best eyesight at age 20 had a lower increase in the need for corrective lenses than the population with visual acuity between 0.9 and 0.7 at age 20. These results suggest an increased risk of visual acuity loss in pilots over time as a result of the lower vision standards for student pilots in the JASDF.

Adult↗
PubMed1999

Spatial performance of unilateral vestibular defective patients in nonvisual versus visual navigation.

The purpose of this study was to investigate the effects of unilateral vestibular neurotomy on humans ability to perform navigation tasks. These tasks provided self-motion feedback by way of either locomotor activity only (nonvisual navigation or "locomotor task") or visual motion cues only (visually simulated navigation or "visual task"). After exploration of an environment in which 4 locations were marked by different objects, subjects attempted to navigate to those locations either by reproducing the same paths as those followed during exploration, by reversing routes, or by making spatial inferences (shortcuts). Vestibular defective patients were tested one day before surgical treatment and during the recovery time course following unilateral vestibular nerve lesion (1 week, 1 month, and 3 month later). Their performance was assessed by measuring turn error and distance error in both navigation tasks and was compared to that of control subjects tested 4 times at similar time intervals. Turn error in the reproduction of previously explored routes in the locomotor task was lower in patients before surgery than in controls, suggesting the existence of compensatory processes. In the acute stage (1 week) after unilateral vestibular lesion, turn error was greater in patients than in controls for the highest level of mental representation (spatial inferences or reversing routes); impairment at making accurate rotations had disappeared by 1 month after vestibular lesion in both navigation tasks. These results point to the role of vestibular cues, in interaction with other sensory modalities, in the elaboration of an accurate internal representation of the environment. In addition, they suggest that unilateral suppression of vestibular information would induce transitory spatial memory disorganization at a high level of information processing.

Distance Perception↗
PubMed2000

Vestibular capture of the perceived distance of passive linear self motion.

The relative role of visual and vestibular cues in determining the perceived distance of passive, linear self motion were assessed. Seventeen subjects were given cues to constant acceleration motion: either optic flow, physical motion in the dark or combinations of visual and physical motion. Subjects indicated when they perceived they had traversed a distance that had been previously indicated either visually or physically. The perceived distance of motion evoked by optic flow was accurate relative to a visual target but was perceptually equivalent to a shorter physical motion. The perceived distance of physical motion in the dark was accurate relative to a previously presented physical motion but was perceptually equivalent to a much longer visually presented distance. The perceived distance of self-motion when both visual and physical cues were present was perceptually equivalent to the physical motion experienced and not the simultaneous visual motion even when the target was presented visually. We describe this dominance of the physical cues in determining the perceived distance of self motion as "vestibular capture".

Adult↗
PubMed1999

Retinal location and its effect on the spatial distribution of visual attention.

A series of studies tested for distractor compatibility effects across wide target/distractor distances (0.6 degree to 20 degrees of visual angle). The effects of precue condition, constant/varied target location, horizontal/vertical distractor distance, and foveal/peripheral presentation were studied. Results show strong compatibility effects across wide distances when distractors are at peripheral retinal locations. When both stimuli were presented at the same peripheral location in opposite hemifields, compatibility effects were evident within an area of at least 2.5 degrees of visual angle. In contrast, when foveally placed distractors were used, compatibility effects were found primarily with target letters positioned near. The findings suggest that distance effects are not homogeneous across retinal location.

Adult↗
PubMed2000

Spatial generalization from learning dynamics of reaching movements.

When subjects practice reaching movements in a force field, they learn a new sensorimotor map that associates desired trajectories to motor commands. The map is formed in the brain with elements that allow for generalization beyond the region of training. We quantified spatial generalization properties of these elements by training in one extreme of the reachable space and testing near another. Training resulted in rotations in the preferred direction (PD) of activation of some arm muscles. We designed force fields that maintained a constant rotation in muscle PDs as the shoulder joint rotated in the horizontal plane. In such fields, training in a small region resulted in generalization to near and far work spaces (80 cm). In one such field, the forces on the hand reversed directions for a given hand velocity with respect to the location of original training. Despite this, there was generalization. However, if the field was such that the change in the muscle PDs reversed as the work spaces changed, then performance was worse than performance of naive subjects. We suggest that the sensorimotor map of arm dynamics is represented in the brain by elements that globally encode the position of the arm but locally encode its velocity. The elements have preferred directions of movement but are modulated globally by the position of the shoulder joint. We suggest that tuning properties of cells in the motor system influence behavior and that this influence is reflected in the way that we learn dynamics of reaching movements.

Adult↗