bluuebunny/crossref_metadata_2025_split huggingface dataset:
Holding an Object: Kinesthesia Does Not Influence the Visually Perceived Size
Authors: Brenner E , Smeets J B J , van Damme W J 
Published: December 2015

Because of the inverse relationship between an object's distance and its retinal image size, visual judgments of size require information on distance. Holding an object can obviously influence where one considers it to be. Does kinesthetic information on the posture of one's arm influence visual judgments of the object's size? Subjects were given a 5 cm cube at which they were asked to look before the experiment started, and to hold under the table in their left hand during the experiment. In their right hand, they held a rod behind a mirror. A simulated cube was presented binocularly—at the tip of the rod—via the mirror. Each presentation started with the subject placing the rod somewhere on a surface behind the mirror. The simulated cube appeared at that position (or 2.5 cm closer or further away) for 4 s, after which the subject had to indicate whether the cube he/she had seen was larger, the same, or smaller than the reference. The size of the simulated cube was varied between trials. Whether the simulated cube was closer, at the same position, or further than the rod influenced the point of subjective equality (the size of the simulation at which subjects judged it to match the reference). However, the average distance between the subject and the simulation was also different. When the latter differences were taken into account (by selecting data with the same average distance between the subject and the simulation) the abovementioned influence of the distance between the rod and the simulated cube disappeared.
A Perplexing Puzzle Involving Perception of Straight Ahead
Authors: Enright J T 
Published: December 2015

Perception of visual direction was investigated by requiring subjects repeatedly to adjust a single small light, in an otherwise darkened room, to perceived ‘straight ahead’. This task presumably requires comparing concurrent extra-retinal information (either proprioception or an efference copy) with an internally stored ‘standard’ of comparison. Moment-to-moment precision in that performance is remarkably good, with median threshold (standard deviation) of 47 arc min. Nevertheless, the responses often involved a monotonic shift of direction over a few minutes during a test session in this reduced visual environment. These trends led to final settings that were immediately recognised as grossly erroneous when the room was relit, implying that the presumptive internal standard of comparison, while unstable, can be rapidly updated in a full visual environment. There are clear similarities between this phenomenon and the sudden ‘visual capture’ that occurs in a re-illuminated room, following distortions of visual direction that arose in a similarly reduced setting for subjects whose extraocular muscles were partially paralysed (Matin et al, 1982 Science216 198 – 201). In both cases, the visual stimuli that underlie rapid recalibration are unknown. Among the several possibilities that can be imagined, the strongest candidate hypothesis for this calibration of the straight-ahead direction is that, during fixation in a lit room, one utilises the directional distribution of image motion that arises because of microscale drift of the eye, as it moves toward its equilibrium orientation, much as a moving observer can use optic flow to evaluate ‘heading’ (the dynamic analogue of ‘straight ahead’).
Stochastic Properties of Segmentation-Rivalry Alternations
Authors: Arrington K F 
Published: December 2015

Segmentation rivalry is the alternation of perceived depth that occurs when depth information from, eg, occlusion and stereo disparity cues are inconsistent (Arrington and Held, 1995 ARVO Abstracts). It was conjectured that the rivalry is based on reciprocal inhibition between end-stopped cell populations that code the same spatial location but opposite direction of surface segmentation in depth. Here the stochastic properties of these depth alternations are analysed and compared to prior analysis [Blake, Fox, and McIntyre, 1971 Journal of Experimental Psychology88 (3)] of binocular rivalry alternations, which suggested that successive phase durations are approximated by a theoretical gamma distribution: f( x)= b a/ Elog \Gamma( a) x a−1exp(− bx). Phenomenally in-front (F) versus phenomenally behind (B) phase durations during segmentation rivalry were collected at 2 min arc stereo disparity that produces a maximal alternation rate and ∼50% duty cycle. Least-square error fit to the two duration data sets was very good (F: a=3.69, b=0.514; B: a=6.54, b=0.780) and the chi-square goodness-of-fit showed insignificant ( p<0.01) departures from the theoretical gamma distribution when the histogram was smoothed and in some cases when it was not smoothed. (Mathematical expressions may not appear as intended)
Illusory Optic Flow Transformation with Binocular Vision
Authors: Grigo A , Lappe M 
Published: December 2015

We investigated the influence of stereoscopic vision on the perception of optic flow fields in psychophysical experiments based on the effect of an illusory transformation found by Duffy and Wurtz (1993 Vision Research33 1481 – 1490). Human subjects are not able to determine the centre of an expanding optic flow field correctly if the expansion is transparently superimposed on a unidirectional motion pattern. Its location is rather perceived shifted in the direction of the translational movement. Duffy and Wurtz proposed that this illusory shift is caused by the visual system taking the presented flow pattern as a flow field composed of linear self-motion and an eye rotation. As a consequence, the centre of the expansional movement is determined by compensating for the simulated eye rotation, like determining one's direction of heading (Lappe and Rauschecker, 1994 Vision Research35 1619 – 1631). In our experiments we examined the dependence of the illusory transformation on differences in depth between the superimposed movements. We presented the expansional and translational stimuli with different relative binocular disparities. In the case of zero disparity, we could confirm the results of Duffy and Wurtz. For uncrossed disparities (ie translation behind expansion) we found a small and nonsignificant decrease of the illusory shift. In contrast, there was a strong decrease up to 80% in the case of crossed disparity (ie translation in front of expansion). These findings confirm the assumption that the motion pattern is interpreted as a self-motion flow field: only in the unrealistic case of a large rotational component present in front of an expansion are the superimposed movements interpreted separately by the visual system.
Stereoscopic Transparency and Segregation in Depth
Authors: Lankheet M J M , Palmen M 
Published: December 2015

We previously described the spatiotemporal requirements for binocular correlation in stereopsis using sinusoidal gratings-in-depth (Lankheet and Lennie, 1996 Vision Research36 527 – 538). The use of smooth sinusoidal surfaces emphasised the effects of spatial and temporal integration. Binocular correlation, however, depends not only on integration, but also on segregation at depth discontinuities. In the present experiments we therefore investigated segregation-in-depth, using random dot stereograms that depicted two transparent frontoparallel planes positioned symmetrically on either side of a binocular fixation point. Sensitivity for segregating the two planes was established by adding Gaussian distributed disparity noise to the disparities specifying the planes, and finding the noise amplitude that rendered transparency just detectable. The stimuli consisted of dynamic random-dot displays (dot lifetime 4 frames, at a frame rate of 67 Hz), generated in real time by a Macintosh computer, displayed on a television monitor, and viewed through a stereoscope. We used a method of constant stimuli and a 2AFC procedure. Two transparent planes were presented in one interval, and a single plane, with Gaussian distributed disparity values spanning the same range, was presented in the other. Segregation of stationary patterns was optimal for disparity differences of about ±9 min arc. Differences smaller than ±3 min arc and larger than about ±18 min arc could not be resolved. Motion contrast between the two patterns greatly facilitated segregation in depth. The facilitating effect increased with the difference in motion directions. The optimal speed varied with the difference in disparity.
Overt Visual Attention in Parkinson's Disease
Authors: Lee A C , Harris J P , Calvert J E 
Published: December 2015

The ability of Parkinsonian (PD) patients to control overt visual attention was investigated, by measuring reaction time to a visual stimulus presented at different distances (1.5 deg, 6 deg, and 12 deg) and directions (left or right) from a central fixation point. Prior to the onset of the target stimulus (a square), a cue stimulus appeared just above the fixation point. With equal probability, the arrow pointed to the left, or to the right, or was ambiguous (with two heads). On 20% of their presentations, the left and right arrows pointed in the direction opposite to where the target was to appear. Subjects were informed that 20% of cues would be misleading, and correcting lenses were used to optimise their visual acuity. In previous work with a similar paradigm, only one target eccentricity was used, and subjects were not refracted, leaving open the possibility that PD subjects had more difficulty in seeing the cues and targets. The eight PD subjects had longer reaction times than age-matched normal controls (and were relatively slower for the more eccentric targets), but made fewer errors in all conditions. In particular, they were more accurate than the controls on the presentations when the cue was misleading or ambiguous, suggesting that the PD group were ignoring the cue. It seems unlikely that the subjects discriminate the direction of the cues, given the use of optical correction, and they reported seeing the cues. Our data are consistent with those of other workers who have described a similar ‘disengagement of attention’ in PD (Clark et al, 1989 Neuropsychologia27 131 – 140) and attributed it to decreased catecholaminergic activity following destruction of midbrain structures (Wright et al, 1990 Neuropsychologia28 151 – 159).
Head-Mounted Video Camera System in Testing Multihandicapped Children with Low Vision
Authors: Leinonen M T , Koskinen L 
Published: December 2015

Vision testing with multihandicapped children is more difficult than with normally developed children: the child's ability to concentrate in the test situation is often markedly reduced, or the child is not capable of communicating with the examiner in the normal way owing to deficiencies in motor skills, hearing, or speech. Often observation of the eyes and face is difficult because of bent-down sitting position caused by poor control of head and neck. By recording the test situation on a video tape it is possible to analyse the child's reactions afterwards more accurately. Our video system consists of a miniature video camera attached to the head of the child with a small mirror in front of the camera to provide a picture of the eyes. Simultaneous recording of the eye movements and the fixation target is possible by adjusting the position of the mirror so that it covers the view of the camera only partially. With the aid of a second, conventional video camera, we get an overview picture of the test situation. This picture is combined with the image of the miniature camera on the child's head and recorded on a video tape. With our video system it is possible to see the eye movements even when the child's head is bent-down or the child is moving in the examination room. It also allows the use of full-field stimuli covering the eyes as in examination of the optokinetic nystagmus. The eye - hand coordination can also be monitored on the video tape.
Colour Perception 1978–1997
Authors: Mollon J D 
Published: December 2015

In the past twenty years, the spectral sensitivities of the three types of cone have been established with some certainty: direct measurements by microspectrophotometry and electrophysiology are in fair agreement with psychophysical estimates. Particularly significant was the publication of DNA sequences for the four opsins of the human eye, by Jeremy Nathans and colleagues in 1986. This work was soon to transform the understanding of retinitis pigmentosa and other retinal dystrophies, and it has given many insights into the evolution of colour vision; but, curiously, the explanations of dichromacy and anomalous trichromacy have not proved as straightforward as we all expected in 1986. What is clear, however, is that normal colour vision exhibits a genetic polymorphism: much of the intersubject variance in colour matches can be traced to differences in the amino-acid sequence of the opsins for the long-wave and middle-wave cone pigments. The last two decades have seen a major change in the status of opponent processes. In the 1970s it was still common for professors to tell undergraduates that the Young - Helmholtz theory of colour vision held at the receptor level and the Hering theory at the level of the retinal ganglion cells. It is now clear that the chromatically antagonistic processes revealed electrophysiologically and psychophysically in the early visual system do not correspond to the red - green and yellow - blue processes that Hering postulated on the basis of phenomenological observations. The existence of four unique hues is today one of the unexplained mysteries of colour science. In one salient respect, research in colour vision has been changed by instrumental advances. Computer-controlled monitors (though offering splendid pitfalls to the unwary) have allowed the study of spatially and temporally complex chromatic displays, notably in the field of colour constancy. Most recently there has been interest in the chromatic statistics of natural scenes: how well is the visual system matched to the statistics of the world and can it adapt to the gamut of chromaticities present in a given scene?
The Accuracy of Saccadic and Perceptual Decisions in Visual Search
Authors: Eckstein M P , Beutter B B , Stone L S 
Published: December 2015

Saccadic eye movements during search for a target embedded in noise are suboptimally guided by information about target location (Eckstein et al, 1997, paper presented at ARVO). Our goal was to compare the spatial information used to guide the saccades with that used for the perceptual decision. Three observers were asked to determine the location of a bright disk (diameter 21 min arc) in white noise (signal-to-noise ratio 4.2) from among ten possible locations evenly spaced at 5.9 deg eccentricity. In the first of four conditions, observers used natural eye movements. In the three remaining conditions, observers fixated a central cross at all times. The fixation conditions consisted of three different presentation times (100, 200, 300 ms), each followed by a mask. Eye-position data were collected with a resolution of ∼0.2 deg. In the natural viewing condition, we measured the accuracy with respect to the target and the latency of the first saccade. In the fixation conditions, we discarded trials in which observers broke fixation. Perceptual performance was computed for all conditions. Averaged across observers, the first saccade was correct (closest to the target location) for 56±7 (SD) % of trials (chance 10%) and occurred after a latency of 313±56 ms. Perceptual performance averaged 53±4%, 63±4%, 65±2% correct at 100, 200, and 300 ms, respectively. We conclude that, for the signal-to-noise ratio used, at the time of initiation of the first saccade there is little difference between the amount of information about target location available to the perceptual and saccadic systems.
In Congenital Nystagmats, Reading Text with Rapid Serial Visual Presentation (RSVP) Reduces Mean Eye Velocity
Authors: Aquilante K , Wyatt H , Yager D 
Published: December 2015

Most low-vision subjects read text faster from an RSVP display than they do with full PAGE reading. This result has been confirmed with a group of subjects with congenital nystagmus (Plass and Yager, 1995, paper presented at ARVO). The present experiment was intended to determine whether reading with RSVP also reduced the severity of the nystagmus, which may have contributed to the faster reading rates. Eye position and velocity of congenital nystagmats were recorded with an infrared reflection technique, sampled at 40 s−1. Recordings were made in three conditions: (1) passively viewing a blank computer monitor; (2) silently reading full PAGE text at a size of approximately four times Snellen acuity; (3) silently reading RSVP text at the same size, at about 200 words min−1. We found that: (1) in frequency histograms of instantaneous eye velocities at 25 ms intervals, the full width at half height was an average of 60% smaller for RSVP reading compared to PAGE; (2) with a window of ±5 to 20 deg s−1, depending on the subject's baseline eye velocity, the number of epochs that were at least 75 ms in length, and the total time in these epochs, were significantly greater during RSVP reading than during PAGE reading or viewing a blank screen. We conclude that reading with RSVP reduces nystagmus, and may contribute to greater reading speed.
Even Experienced Drivers Have the Wrong Concept about How to Change Lanes
Authors: Wallis G M , Chatziastros A , Bülthoff H H 
Published: December 2015

Imagine changing lanes on a motorway, and in particular the series of angles through which the steering wheel passes in completing the manoeuvre. The vast majority of us describe turning the wheel once and then returning the wheel to the middle position. This is wrong, because we have failed to describe the appropriate symmetrical motion of the steering wheel in the opposite direction required to straighten the car. To investigate this misconcept and so as to determine the type of motor programs used during steering, we tested the ability of subjects to change lanes with and without visual feedback. Five licensed drivers drove in a simulated environment projected on a 180° screen using a force-feedback steering wheel. A straight four-lane motorway appeared alternately with normal (daylight) or zero visibility (dark tunnel). In both conditions subjects were asked to change lanes—either to the left or to the right. In the condition without visual feedback no other feedback about performance was given. Without visual feedback the results showed a predictable increase in variance in the final heading but also suggested a systematic deviation of heading towards the direction of the lane change ( p<0.001), due to the subjects' failure to complete the lane changing manoeuvre. Hence, we conclude that despite the highly practised nature of the task of lane changing, it is not stored as a complete motor program, but is instead achieved by the interplay of a simple steering program and visual feedback about current heading and location on the road.
Text Font Affects Reading Speed at a Low Luminance but Not at a High Luminance
Authors: Yager D , Aquilante K , Plass R 
Published: December 2015

We are beginning a series of studies in which we shall investigate which characteristics of text fonts may be successful in allowing text to be read with different kinds of degradations that may be experienced by low-vision patients. As a first attempt to simulate one of the problems that certain patients might have, we measured reading speeds with two proportionally spaced fonts at a high photopic luminance (146 cd m−2) and at a very low luminance (0.146 cd m−2). We used the RSVP (rapid serial visual presentation) reading method, which eliminates the need for scanning eye movements. The two fonts were ‘Swiss’, a simple sans-serif font, and ‘Dutch’, a serif font similar to Times Roman, both presented at the 20/80 size; letters were white on black, with a contrast of 0.94. Subjects were young, normally sighted high-school and optometry-college students. The reading speed results from 47 subjects were as follows, for four conditions: high luminance, Swiss 531 and Dutch 540 words min−1; low luminance, Swiss 479 and Dutch 429 words min−1. At the high luminance, there is no significant difference between reading rates. There is a significant advantage for the Swiss font at the low luminance: p=0.005. There may be a significant difference in reading speed with different fonts when the patient's perceptions are degraded by disease and/or aging processes. Other parameters to be investigated with this method include contrast, size, blur, and visual field position. The simulation results will suggest parameter values to test on low-vision patients.
Gaze-Accuracy during Monocular and Binocular Viewing
Authors: Steinman R M , Forofonova T I , Epelboim J , Stepanov M R 
Published: December 2015

Epelboim et al (1996 Vision Research35 3401 – 3422) reported that cyclopean gaze errors were smaller than either eye's during tapping and looking-only tasks. This raised two questions: (i) does cyclopean gaze accuracy require binocular input, and (ii) when only one eye sees, is its gaze more accurate than the patched eye's? Most oculomotorists probably expect an affirmative answer to both. Neither expectation was fulfilled. The Maryland Revolving Field Monitor recorded, with exceptional accuracy, eye movements of two unrestrained subjects tapping or only looking, in a specified order, at four randomly positioned LEDs, with monocular or binocular viewing. Subjects either tapped with their finger tips naturally, or unnaturally via a rod (2 mm diameter, 1.5 cm long), glued to a sewing thimble. Instructions were to be fast, but make no order errors. With binocular viewing, cyclopean gaze accuracy was best during looking-only. During natural tapping, gaze errors increased, becoming no smaller than success required. Both tasks were learned equally fast, but as expected, the younger subject (aged 27 years) performed ∼ 40% faster than the older subject (aged 69 years). Unnatural, monocular viewing produced odd results, eg cyclopean gaze error was smallest when only one eye could see in some conditions. Only the older subject served in the unnatural tapping task because the younger's errors were too close to his gaze control limit. The older subject, who was suitable, reduced his cyclopean gaze error by 56%, from 1.4 to 0.9 deg. These results support our claim that the gaze error allowed is adjusted to the visuomotor demands of different tasks.