A simple infrared photocell device and its interface to an Apple computer

This paper describes a simple infrared photocell circuit that is inexpensive and easy to construct. The light source and detector are housed inexpensively and are focused so the light and detector may be separated over significant distances. The circuit may be used in a variety of conditions, including total darkness and bright fluorescent lighting, without having to readjust or recalibrate the circuitry. Output from the circuit may be used to drive other transistors or electromechanical relays. With minimal additional circuitry and hardware the signal may be interfaced with an Apple computer.     

"A moment's monument": the central vision of Italian sculptor Medardo Rosso (1858-1928)

One of the basic limitations on visual perception is that it is impossible, in any given moment, to see the world sharply and full of colors beyond the central area of the visual field. This fact was popularized and brought to the attention of artists in the nineteenth century. To accurately represent the 'impression', or vision of a single glance, an artistic work should contain only a central area in focus surrounded by a progressively greater blur. The work of the Italian sculptor Medardo Rosso (1858-1928) may be the first artistic representation of differences in central and peripheral acuity. Despite using the medium of sculpture, typically three-dimensional, Rosso conceived of his art as two-dimensional because in a given moment it is possible to view a scene from only one viewpoint. The analysis of Rosso's photographs of his own sculptures emphasizes the areas of detail and relative blur, allowing a reconstruction of his point de vue unique--where the observer should stand when viewing that specific sculpture. We argue that the role of central and peripheral vision in subjective perception is critical to understanding the work of Rosso, aptly defined by critics as monument d'un instant.     

Discounting mechanism underlies extinction illusion

Humans can perceive a coherent visual scene despite a low spatial resolution in peripheral vision. How does the visual system determine whether an object exists in the periphery? We addressed this question by focusing on the extinction illusion in which a disk becomes subjectively invisible when presented at the intersection of grids. We hypothesized that the disk would go unnoticed when the stimuli with and without the disk produced the same strength of visual signals. The visual system would miss the disk by confounding the target signals with the intersection signals that should be discounted. Computational analysis revealed that the energy ratio between the stimuli with and without the disk decreased with stimulus eccentricity and such energy ratio could successfully explain the observer’s d’ to detect the disk. These results indicate that the discounting mechanism relying on stimulus energy determines the awareness toward a peripheral object.     

The effects of concentrated and distributed attention on peripheral acuity

Two experiments studied the peripheral discriminability of a target differing in its line slope (a tilted T) and in its line arrangement (an L) when presented in briefly flashed displays of upright Ts. The results showed that: (a) an L and a tilted T were equal in discriminability when attention was focused or concentrated on one display position, (b) the discriminability of an L decreased while the discriminability of a tilted T was not statistically significantly affected as the number of display positions that attention needed to be paid to increased, and (c) the reaction time to find a disparate tilted T was less than that to find a disparate L. The results are interpreted as supporting the hypothesis that, under distributed attention in peripheral vision, the visual system is more sensitive to differences in line slope than to differences in line arrangement The results are discussed in connection with hypotheses of how selective attention affects the discriminability of a target.     

The constancy of the orientation of the visual field

Evidence is presented that the perceived immobility of the environment during tilting of the head from side to side results from a compensating process. This compensating process operates well only when peripheral vision is present. An objectively stationary environment was, for instance, not perceived as immobile during head tilting when vision was confined to the macular region of the retina. The compensating process could be rapidly altered by exposure to environmental tilting during and dependent on head tilting. Such adaptation had the result that some environmental tilting that normally is perceived led to apparent immobility.     

Rotating trapezia which appear luminous and transparent during reversals

If a rotating trapezium is lit by a visible source at one side, it sometimes reflects light to the observer and sometimes appears dark. This provides information about its orientation which is relevant to the suppression of apparent reversals. Marked suppression does occur if the light is between the observer and the object, but in other cases novel phenomena arise. The onset of light may precipitate corrections, ie discontinuous shifts from an illusory percept to a veridical one. At certain stages the object may also appear to be transparent and luminous, particularly if a bar has been passed through it: the bar then appears to be visible through the object. The effects illustrate the limited use vision makes of seemingly excellent sources of information, but they also indicate that the problem may lie in misplaced sophistication rather than crudity.     

The functional role of central and peripheral vision in the control of posture

Three experiments were conducted to investigate the role of central and peripheral vision (CV and PV) in postural control. In Experiment 1, either the central or peripheral visual field were selectively stimulated using a circular random dot pattern that was either static or alternated at 5 Hz. Center of foot pressure (CoP) was used to examine postural sway during quiet standing under both CV and PV conditions. The results showed that, when the visual stimulus was presented in the periphery, the CoP area decreased and more so in the anterior-posterior (AP) than in the medio-lateral (ML) direction, indicating a characteristic directional specificity. There was no significant difference between the static and dynamic (alternating) conditions. Experiment 2 investigated the directional specificity of body sway found in Experiment 1 by having the trunk either be faced toward the stimulus display or perpendicularly to it, with the head always facing the display. The results showed that the stabilizing effect of peripheral vision was present in the direction of stimulus observation (i.e., the head/gaze direction), irrespective of trunk orientation. This suggested that head/gaze direction toward the stimulus presentation, rather than a biomechanical factor like greater mobility of the ankle joint in AP direction than in ML direction, was essential to postural stability. Experiment 3 further examined whether the stabilizing effect of peripheral vision found in Experiments 1 and 2 was caused because more dots (500) were presented as visual cues to the peripheral visual field than to the central visual field (20 dots) by presenting the same number of dots (20) in both conditions. It was found that, in spite of the equal number of dots, the postural sway amplitudes were larger for the central vision conditions than for the peripheral vision conditions. In conclusion, the present study showed that peripheral rather than central vision contributes to maintaining a stable standing posture, with postural sway being influenced more in the direction of stimulus observation, or head/gaze direction, than in the direction of trunk orientation, which suggests that peripheral vision operates primarily in a viewer-centered frame of reference characterized by the head/gaze direction rather than in a body-centered frame of reference characterized by the anatomical planes of the body.     

Active and passive scene recognition across views.

Recent evidence suggests that scene recognition across views is impaired when an array of objects rotates relative to a stationary observer, but not when the observer moves relative to a stationary display [Simons, D.J., Wang, R.F., 1998. Perceiving real-world viewpoint changes. Psychological Science 9, 315-320]. The experiments in this report examine whether the relatively poorer performance by stationary observers across view changes results from a lack of perceptual information for the rotation or from the lack of active control of the perspective change, both of which are present for viewpoint changes. Three experiments compared performance when observers passively experienced the view change and when they actively caused the change. Even with visual information and active control over the display rotation, change detection performance was still worse for orientation changes than for viewpoint changes. These findings suggest that observers can update a viewer-centered representation of a scene when they move to a different viewing position, but such updating does not occur during display rotations even with visual and motor information for the magnitude of the change. This experimental approach, using arrays of real objects rather than computer displays of isolated individual objects, can shed light on mechanisms that allow accurate recognition despite changes in the observer's position and orientation.     

Re‐acquisition of upright vision while wearing visually left–right reversing goggles1

Abstract: The present research aimed to identify the important factor that makes it difficult to re‐acquire upright vision when wearing visually transposed goggles. The author wore left‐right reversing goggles and up‐down reversing goggles each for 14 days in 1986 and in 1990, respectively. When lying on one side with the left‐right reversing goggles on, the observer could get upside‐down vision, which made it possible to compare the difficulty of attaining upright vision when wearing up‐down reversing goggles. The only difference between the two situations is the dimension of the body image to be exchanged: The observer had to exchange the left and right halves of his body in the former situation and had to exchange along the top‐bottom axis of body in the latter situation. Introspective data revealed that attaining an upright sense is easier in the former situation; this means that the asymmetrical structure of our body in the top‐bottom dimension is an important factor in the difficulty of re‐acquiring upright vision.     

Influence of reference frames on asymmetries in Troxler's effect

In 1804, Troxier discovered that, when an observer fixates on a point in central vision and attends to a peripheral stationary stimulus, the peripheral stimulus eventually fades from awareness. This phenomenon is known as Troxler's effect and is allegedly influenced by spatial attention. Asymmetries in Troxler's effect along horizontal and vertical meridian were a recent discovery. However, viewer- and environment-centered reference frames were aligned in prior studies, making it impossible to assess whether asymmetries correspond to viewer- versus environment-centered coordinate systems. This study was undertaken to (a) replicate the asymmetries in the upright condition among 39 participants without health issues and (b) use the asymmetrics to test contrasting predictions made by viewer- and environment-centered coordinate systems when they are decoupled using an experimental head-tilt condition. The horizontal and vertical asymmetries were replicated and consistent with a viewer-centered rather than an environment-centered reference frame.     

Hue discrimination in peripheral vision under conditions of dark and light adaptation

Rod interference is a possible factor contributing to the elevation of chromatic threshold in peripheral vision. It was found that light adaptation lowered peripheral chromatic thresholds. This result was interpreted as being due to the lowering of rod sensitivity. It was also found that light in the photochromatic interval appeared blue, indicating that rods may add a blue component to peripheral color vision.     

Asymmetric object substitution masking

Object substitution masking occurs when a lateral mask persists beyond the duration of a target, reflecting reentrant processes in vision (V. Di Lollo, J. Enns, & R. Rensink, 2000). The authors studied whether substitution masking is location specific and whether it is symmetric around the target. A brief circular display of letters was presented along with a mask that designated the target. The mask was centered on the target or 1.1 degrees to the central or to the peripheral side. Substitution masking was found even when the target and the mask were at different locations. It was asymmetric and stronger when the mask was to the peripheral side of the target than to the central side. Asymmetric substitution was observed using various masks. It could not be explained by retina acuity gradients and was not attenuated by focused attention. The authors propose that target selection triggers an asymmetric inhibitory surround that is stronger toward the central side of the target.     

光照的警觉性作用

光照除了传统的视觉作用外, 还具有一定的非视觉效应, 包括调节昼夜节律、褪黑素分泌和警觉性等生理功能和行为表现。随着光照对生理节律影响研究的不断深入, 近来很多学者开始关注光照的警觉性作用。我们根据最新研究进展总结了：(1)警觉性的测量工具; (2)光照强度、时长、时间点、波长、色温等对光照警觉性作用的影响; (3)光照在治疗情绪障碍、调节生理节律、完善办公照明方面的应用; (4)提出了继续探讨光照警觉性作用的神经机制、优化参数特征和探讨混淆变量的研究方向。     

What aspects of vision facilitate haptic processing?

We investigate how vision affects haptic performance when task-relevant visual cues are reduced or excluded. The task was to remember the spatial location of six landmarks that were explored by touch in a tactile map. Here, we use specially designed spectacles that simulate residual peripheral vision, tunnel vision, diffuse light perception, and total blindness. Results for target locations differed, suggesting additional effects from adjacent touch cues. These are discussed. Touch with full vision was most accurate, as expected. Peripheral and tunnel vision, which reduce visuo-spatial cues, differed in error pattern. Both were less accurate than full vision, and significantly more accurate than touch with diffuse light perception, and touch alone. The important finding was that touch with diffuse light perception, which excludes spatial cues, did not differ from touch without vision in performance accuracy, nor in location error pattern. The contrast between spatially relevant versus spatially irrelevant vision provides new, rather decisive, evidence against the hypothesis that vision affects haptic processing even if it does not add task-relevant information. The results support optimal integration theories, and suggest that spatial and non-spatial aspects of vision need explicit distinction in bimodal studies and theories of spatial integration.     

Photoelectric recording of pigeon-peck responses to computer-driven visual displays

A small photocell mounted on a pigeon’s beak signalled the location of pecks to an oscilloscopic display. An on-line LINC computer produced the stimulus display and recorded responses. The method was developed for the study of visual search, but it is applicable to other perceptual or cognitive problems.     

Visual and nonvisual information disambiguate surfaces specified by motion parallax.

Motion parallax has been shown to be an effective and unambiguous source of information about the structure of three-dimensional (3-D) surfaces, both when an observer makes lateral movements with respect to a stationary surface and when the surface translates with respect to a stationary observer (Rogers & Graham, 1979). When the same pattern of relative motions among parts of the simulated surface is presented to a stationary observer on an unmoving monitor, the perceived corrugations are unstable with respect to the direction of the peaks and troughs. The lack of ambiguity in the original demonstrations could be due to the presence of (1) non-visual information (proprioceptive and vestibular signals) produced when the observer moves or tracks a moving surface, and/or (2) additional optic flow information available in the whole array. To distinguish between these two possibilities, we measured perceived ambiguity in simulated 3-D surfaces in situations where either nonvisual information or one of four kinds of visual information was present. Both visual and nonvisual information were effective in disambiguating the direction of depth within the simulated surface. Real perspective shape transformations affecting the elements of the display were most effective in disambiguating the display.     

Visual and nonvisual information disambiguate surfaces specified by motion parallax

Motion parallax has been shown to be an effective and unamhiguous:source of information about the structure of three-dimensional (3-D) surfaces, both when an observer makes lateral movementswith respect to a stationary surface and when the surface translates with respect to a stationary observer (Rogers & Graham, 1979). When the same pattern of relative motions among parts of the simulated surface is presented to a stationary observer on an unmoving monitor, the perceived corrugations are unstable with respect to the direction of the peaks and troughs. The lack of ambiguity in the original demonstrations could be due to the presence of (1) non-visual information (proprioceptive and vestibular signals) produced when the observer moves or tracks a moving surface, andlor (2) additional optic flow information available in the whole array. To distinguish between these two possibilities, we measured perceived ambiguity in simulated 3-D surfaces in situations where either nonvisual information or one of four kinds of visual information was present. Both visual and nonvisual information were effective in disambiguating the direction of depth within the simulated surface. Real perspective shape transformations affecting the elements of the display were most effective in disambiguating the display.     

The Effect of Retinal Eccentricity on Perceiving Collision Impacts

Three experiments examined the role of central and peripheral vision in collision detection and control of braking. Displays simulated observer movement over a ground plane toward obstacles lying in the observer's path (Experiments 1 & 3) or toward a vertical 2-D plane (Experiment 2). Optical expansion was depicted under the constraint that remains constant throughout the approach. Displays employed in Experiments 1 and 2 were masked centrally (peripheral vision) or peripherally (central vision) with mask size ranging from 10° to 30° in diameter in steps of 5°. Participants responded to the optical pattern engendered by with more consistency in the peripheral vision condition than in the central vision condition. Experiment 3 further examined the peripheral advantage by masking the displayed peripheral region from 20% to 80%. Largely unaffected performance across masked areas of the periphery confirmed that the efficacy of the peripheral retina does not lie in more extensive flow vectors but in its inherent sensitivity to optical consequences engendered by . These results were compared with psychophysical findings in self-motion perception and clinical findings in patients with partial vision loss.     

Some findings on prospect and refuge: I

Prospect and refuge theory suggests that preferences for environments are based on prospect (the unimpeded opportunity to see) and refuge (the opportunity to hide). This article reports two experiments on how well four factors derived from prospect and refuge theory predicted responses of comfort or liking. The factors were prospect (depth of view), refuge (presence of protective regions in front of the observer or occluding edges that might indicate possibilities of escape), direction of light (either front lighting or back lighting), and venue (natural or built environments). Exp. 1 had 16 landscape scenes and 29 participants; Exp. 2 had 16 landscapes, 14 rooms, and 18 participants. Empirical support was obtained for the claim that people will like gazing out over scenes of distant mountains. For venue, built scenes were preferred over scenes of nature. Results for refuge were ambiguous, and those for di rection of light were nill.     

The role of central and peripheral vision in perceiving the direction of self-motion.

Three experiments were performed to examine the role that central and peripheral vision play in the perception of the direction of translational self-motion, or heading, from optical flow. When the focus of radial outflow was in central vision, heading accuracy was slightly higher with central circular displays (10 degrees-25 degrees diameter) than with peripheral annular displays (40 degrees diameter), indicating that central vision is somewhat more sensitive to this information. Performance dropped rapidly as the eccentricity of the focus of outflow increased, indicating that the periphery does not accurately extract radial flow patterns. Together with recent research on vection and postural adjustments, these results contradict the peripheral dominance hypothesis that peripheral vision is specialized for perception of self-motion. We propose a functional sensitivity hypothesis--that self-motion is perceived on the basis of optical information rather than the retinal locus of stimulation, but that central and peripheral vision are differentially sensitive to the information characteristic of each retinal region.