Obstacle avoidance in novel visual environments improved by variable practice training

Motor performance on simple tasks improves after training in variable practice. We asked if locomotor skill during an obstacle-avoidance task in a novel sensorimotor environment improved through training in variable practice on other complex tasks. 40 normal adults practiced gross motor skills while wearing either sham lenses, one of several visual distortion lens (constant practice), or three different visual distortion lenses (variable practice). Posttests on obstacle avoidance with novel lenses showed significantly better scores with variable practice and one of the constant groups vs sham lenses. Constant and variable practice groups did not differ. Thus, performance in a novel environment improves after training on similar type novelty, even when practice and test conditions differ. Constant practice was effective only if the subjects used the lens efficacious in training. Variable practice increases the likelihood of efficacious training when adaptive performance is required in a novel environment.     

The effects of periodic visual occlusion on ball catching

Four experiments were conducted to examine the effects of periodic visual occlusion on one-handed ball catching. Tennis balls were projected one at a time over distances of 8-12 m, and liquid-crystal visual occlusion spectacles provided intermittent vision by opening and closing the lens shutters at different frequencies. As well as frequency, we manipulated duty cycle, or the proportion of time that the lenses were open. Generally, catching performance deteriorated as frequency was reduced. Although longer visual samples (i.e., increased duty cycle) mediated this effect to some extent, the most potent variable was the time between visual samples; performance deteriorated rapidly when this interval was greater than 80 ms (i.e., 10 Hz with 20-ms lens open times). Presumably this occurred because subjects had difficulty integrating visual information separated by longer temporal intervals.     

Eye contact as a setting event for infant learning

Three-month-old human infants received social reinforcement contigent upon each vocalization. The experimenter wore eye glasses with lenses composed of clear acetate, skin-toned opaque shields, or life-size photographs of the experimenter's eyes (with direct or averted gaze), and maintained visual contact with the infant's eyes (via pinholes in the lenses) during all sessions. Each group of three subjects experienced two of the four possible lens conditions. During baseline and extinction sessions vocalization rate was quite similar under each lens condition. During conditioning sessions, however, vocalizations exceeded baseline rates in all but the opaque lens condition. In this study eye contact was neither a reinforcing, discriminative, nor eliciting stimulus. Eye contact was a setting stimulus (catalyst) for the response-reinforcement relationship.     

TEACHING YOUNG CHILDREN TO USE CONTACT LENSES

Young children with surgically removed lenses and extreme nearsightedness can benefit from contact lenses, but their parents may need instruction to teach their children to accept lenses. In this study, 4 children under the age of 5 years were taught contact lens wear using a shaping procedure. Compliance was rewarded with praise and tangibles, and noncompliance was followed with brief time-out for 3 of the children and restraint for the 4th. Three children showed high compliance during an initial shaping procedure, with a decrease in compliance during initial insertion of the lenses. At 3- to 10-month follow-up, levels of compliance were high. Insertion and removal of lenses were accomplished in substantially less time, with little crying and no need for time-out. All 3 children continue to use the lenses daily, and 2 have shown improved visual acuity. The 4th child, who has Down syndrome, showed low levels of compliance with need for physical restraint throughout. Although his parents reported high compliance when he first went home, fitting difficulties and an infection resulted in plummeting of compliance, and contact lens use was discontinued. This procedure has been used successfully at the same hospital with 11 of 13 other children between the ages of 14 months and 7 years 4 months. Implications for selection of suitable candidates for this intervention and ways to decrease costs are discussed.     

Manual localization of lateralized visual targets

The effects of visual field, responding limb and extrapersonal space on the ability to localize visual targets using slow positioning movements of the arm were examined. Special contact lenses were used to lateralize visual information and to make comparisons with localization under monocular control conditions. Subjects made slow positioning movements to place a cursor directly beneath target lights. They saw target lights but not the moving limb during the trial. For directional error, results indicated that subjects were more accurate localizing targets lateralized to the right hemisphere than targets lateralized to the left hemisphere, indicating right hemisphere superiority for localization of visual targets in grasping space. Localization performance was significantly better with the right hand than the left hand. the left hand demonstrated a directional bias to the right of the targets. Responding hand and visual field did not interact. Finally, contrary to subjects' awareness and verbal reports, target localization was not less accurate in lens than in monocular control conditions. This was true for both amplitude and directional error. This is consistent with other studies where visual information about limb position is not available.     

Is optimal vision required for the successful execution of an interceptive task?

The importance of optimal visual function in demanding interceptive tasks is far from established. The aim of the study was to determine whether induced myopic blur and hence sub-optimal visual function would give rise to a detrimental effect on performance in the execution of an interceptive task. The batting performance of grade level cricket players was assessed facing a bowling machine whilst wearing contact lenses of four different refractive conditions (plano (nil), +1.00, +2.00 and +3.00D over-refraction), inducing increasing amounts of myopic blur. Performance for each condition was assessed based both on the shot quality against each delivery judged by a qualified cricket coach blind to each condition, along with an evaluation of the quality of ball-bat contact for each delivery. No significant change was found in batting performance with the introduction of +1.00 and +2.00D of induced myopic blur. A +3.00D over-correction was required before any significant decrease in batting performance was detected, demonstrating that batters needed to be essentially legally blind (as simulated through the use of the +3.00D over-refraction) before there was any significant measurable decrement in batting performance. We concluded that optimal visual correction is not necessarily required for optimal performance in a demanding interceptive task, and that the human perceptual-motor system is capable of compensating for marked alterations in input.     

The use of contact lenses for the lateralisation of visual input in man.

This research demonstrates the use of a new method of investigating lateralised hemisphere functions. Specially designed contact lenses were used, which directed visual input to either the left or the right cerebral hemisphere. These lenses are an advance on previous methods used in investigating hemisphere function in that they enable the subject to react to stimuli without restrictions on movement and without time limitations on the exposure of stimuli. Investigations of language and visual-spatial functions showed that the lenses appeared to be very effective in lateralising verbal and spatial information.     

Effective 3-D shape discrimination survives retinal blur

A single experiment evaluated observers’ ability to visually discriminate 3-D object shape, where the 3-D structure was defined by motion, texture, Lambertian shading, and occluding contours. The observers’ vision was degraded to varying degrees by blurring the experimental stimuli, using 2.0-, 2.5-, and 3.0-diopter convex lenses. The lenses reduced the observers’ acuity from ?0.091 LogMAR (in the no-blur conditions) to 0.924 LogMAR (in the conditions with the most blur; 3.0-diopter lenses). This visual degradation, although producing severe reductions in visual acuity, had only small (but significant) effects on the observers’ ability to discriminate 3-D shape. The observers’ shape discrimination performance was facilitated by the objects’ rotation in depth, regardless of the presence or absence of blur. Our results indicate that accurate global shape discrimination survives a considerable amount of retinal blur.     

Background luminance and input devices on clicking performance with a tablet PC

This study investigated the effects of input devices and background luminance on clicking performance with a Tablet PC. The experiment was designed in complete block design within subjects. Participants were 19 men and 11 women, college students whose ages were 19 to 22 years (M=20.1 yr.). All had 0.8 corrected visual acuity or better and normal color vision. Three kinds of input devices, mouse, light pen, and touchpad, were used in this experiment. An analysis of variance showed that input devices significantly affected clicking performance as did background luminance (contrast ratio) on visual recognition (a higher contrast ratio gave better visual recognition).     

Management of extended-wear contact lenses in infant rhesus monkeys

Infant rhesus monkeys were fitted with extended-wear contact lenses (EWCLs) to correct surgically induced aphakia. The protocol that produced the most favorable experimental outcome, including good lens-wear compliance, involved: (1) custom-made EWCLs with parameters adjusted for each animal, (2) selection for study of neonates who seemed to tolerate EWCLs most naturally, (3) individual housing of monkeys, (4) lens check at 2-h intervals around the clock by trained personnel, (5) a large inventory of EWCLs for each animal, (6) periodic ophthalmologic examinations, and (7) darkroom housing of monkeys during treatment of lens-wear-related incidents. The EWCL is a new tool for studies of the visual system and is a useful complement to existing experimental techniques.     

VIEWERS' PERCEPTIONS OF VELOCITY AND DISTANCE IN TELEVISED EVENTS

Subjects from third-grade, seventh-grade, and college-age levels who differed with respect to photographic skills and knowledge were asked to judge the comparative velocity and distance traveled by two trains on videotape. In each of four comparisons, the velocity and distance traveled by both trains were equal, but photographing the trains with lenses of different focal lengths produced apparent differences between the velocity and distance traveled by the trains. Both children and adults frequently interpreted the effect of lens focal length as actual differences between the two trains in velocity and distance traveled. Hands-on experience with the tools of visual media only slightly mitigated against this tendency. The implications of this study are that many viewers do not understand how television production techniques manipulate perceptual information, and may thus be misled by their use.     

Reading with a filtered fovea: The influence of visual quality at the point of fixation during reading

Reading relies critically on processing text in foveal vision during brief fixational pauses, and high-quality visual input from foveal text is fundamental to theories of reading. However, the quality of visual input from foveal text that is actually functional for reading and the effects of this input on reading performance are unclear. To investigate these issues, a moving, gaze-contingent foveal filtering technique was developed to display areas of text within foveal vision that provided only coarse, medium, or fine scale visual input during each fixational pause during reading. Normal reading times were unaffected when foveal text up to three characters wide at the point of fixation provided any one visual input (coarse, medium, or fine). Wider areas of coarse visual input lengthened reading times, but reading still occurred, and normal reading times were completely unaffected when only medium or fine visual input extended across the entire fovea. Further analyses revealed that each visual input had no effect on the number of fixations made when normal text was read, that adjusting fixation durations helped preserve reading efficiency for different visual inputs, and that each visual input had virtually no effect on normal saccades. These findings indicate that, despite the resolving power of foveal vision and the emphasis placed on high-quality foveal visual input by theories of reading, normal reading functions with similar success using a range of restricted visual inputs from foveal text, even at the point of fixation. Some implications of these findings for theories of reading are discussed.     

The Socioeconomic Status,Intelligence, and Psychometric Pattern of Native-Born White Homeless Men

Build-up of proactive interference (PI) with visual-picture and auditory-verbal input modalities and the subsequent release from PI following a change in modality was investigated in three experiments with boys and girls, as follows: Experiment I (n = 64) at two mean age levels, 7–6 and 10–5; Experiment II (n = 64) at mean age 7–6; and Experiment III (n = 48) at age 11–4. PI build-up occurred in both modalities for all ages tested. Release from PI occurred following a change from auditory to visual input but not following a visual to auditory shift. In the final experiment, this asymmetrical improvement in performance was dependent upon an interaction between the modality of the input and distractor task on the final or release trial; changing to visual input produced a release effect regardless of the distractor task modality, while auditory input was associated with improvement in recall if a visual distractor task was employed whether or not a shift in input modality had occurred. This improvement was hypothesized to represent a decrease in retroactive interference rather than a release from proactive interference.     

New evidence for the zoom lens model using the RSVP technique

A main prediction from the zoom lens model for visual attention is that performance is an inverse function of the size of the attended area. The “attention shift paradigm” developed by Sperling and Reeves (1980) was adapted here to study predictions from the zoom lens model. In two experiments two lists of items were simultaneously presented using the rapid serial visual presentation technique. Subjects were to report the first item he/she was able to identify in the series that did not include the target (the letter T) after he/she saw the target. In one condition, subjects knew in which list the target would appear; in another condition, they did not have this knowledge, having to attend to both positions in order to detect the target. The zoom lens model predicts an interaction between this variable and the distance separating the two positions where the lists are presented. In both experiments, this interaction was observed. The results are also discussed as a solution to the apparently contradictory results with regard to the analog movement model.     

Academic Freedom and Academic Tenure: Can They Survive in the Market Place of Ideas?

Recently academic freedom and academic tenure have been in the media spotlight because of concerns that academic freedom is being misused and that academic tenure provides job security to a select few. First, this paper provides a brief history of these two institutions and follow with an analysis using Stone’s (2002) policy analysis format. Second, this paper examines the university through two lenses: (a) an economic market lens; and (b) a community lens. These two lenses offer contrasting views of the university and help explain the different views of academic freedom and tenure. The authors suggest that faculty make use of the economic model to increase their chances of maintaining tenure in a university atmosphere frequently characterized by a business approach rather than a collegial one. Recommendations for future research are also provided.     

More than meets the eye: Implicit perception in legally blind individuals

Legally blind participants (uncorrected vision of 20/200+) were able to identify a visual stimulus attribute (clock hand position) in the absence of consciously identifying its presence. Specifically, participants—with their corrective lenses removed—correctly guessed the hour-hand position above chance (8%) on a clockface shown on a computer screen. This occurred both when presented in a 1-clockface display (28%), as well as when shown a display containing 4 clockfaces (21%), in which only 1 face contained a hand. Even more striking, hand identification accuracy in the 4-clockface condition was comparable whether the clockface containing the hand was (21%) or was not (20%) correctly identified. That legally blind individuals are capable of identifying stimulus attributes without conscious awareness provides an additional vehicle for exploring implicit perception. Consistent with previous research, the visualsystem can apparently cope with degraded visual input through information available through a(n unconscious) secondary pathway via the superior colliculi.     

Reliance on visual feedback from ocular accommodation on motor skills in children with developmental coordination disorder and typically developing controls

Children with developmental coordination disorder (DCD) present with marked impairments in motor skills, including visual-motor integration. Oculomotor anomalies are more prevalent in children with DCD than typically developing children. Children with DCD further demonstrate altered use of visual feedback compared to typically developing controls. We investigated whether the accommodation system, a key component of the oculomotor system, contributes to visual feedback during fine and gross motor skills performance; and whether children with DCD demonstrate differences in reliance on visual feedback from accommodation. Minus dioptre lenses were used to maximally induce accommodation and impede accommodation dynamics. Children with DCD and typically developing controls performed motor skills tests assessing balance, upper limb coordination, visual-motor performance, gross and fine dexterity. Motor skills performance in controls was significantly affected by impeded accommodation in all tasks. Children with DCD demonstrated reliance on accommodation feedback in upper limb and visual-motor tasks only. Children with DCD may be less reliant on visual feedback obtained from accommodation due to adaptive mechanisms to overcome faulty information in the presence of oculomotor anomalies. These results strengthen our previous findings that accommodation anomalies contribute to motor skills impairment, and suggest that performance on these motor tasks is heavily reliant on visual feedback from accommodation.     

Identification of peripheral visual images in a laterally restricted gaze field

When the peripheral visual field is restricted or distorted, as occurs with certain spectacle lenses, the identification of objects in the periphery requires a coordinated head and eye movement. Initial experiments on the identification of peripheral images under such restrictions show that the degradation in performance is defined by a consistent additional delay in the time required to identify the image correctly. An analysis of the motor movements shows that performance is solely determined by movements of the head; eye movements are sufficiently precise and fast so they do not limit performance. A quantitative model of the identification task was developed and model simulations confirmed the experimental findings that head movement variables, specifically response latency and movement duration, uniquely determine identification performance. Hence, improved performance under these conditions must come from modifications in head-movement control either through training or adaptive processes.     

Gravitational lensing and Hacking's extragalactic irreality

In Extragalactic Reality: The Case of Gravitational Lensing Hacking resumes the discussion of scientific realism from the last chapter of Representing and Intervening. Since the criterion of manipulability cannot be applied to astronomical objects, experimental entity realism seems to be restricted to terrestrial entities. In fact, Hacking explicitly argues against astronomical realism. The case at issue is the existence of gravitational lenses. In this paper, I question Hacking's chief witness for astronomical antirealism: the gravitational lens system “0957+ 561”. It will be shown that Hacking's argumentation is misleading. Discussing astronomical realism as theory realism, Hacking focuses on the question of how to infer the existence of gravitational lenses from the truth of gravitational lens theory. But neither the reconstruction of gravitational lensing in terms of inference to the best explanation (IBE) nor the argument of underdetermination are tenable under closer inspection. My thesis is that a realist account of gravitational lensing can be given by relying on observation, causal capacities and home truths.     

Effects of instruction modality and readback on accuracy in following navigation commands

In 3 experiments, the authors simulated air traffic controllers giving pilots navigation instructions of various lengths. Participants either heard or read the instructions; repeated either all, a reduced form, or none of the instructions; and then followed them by clicking on the specified locations in a space represented by grids on a computer screen. Execution performance for visual presentation was worse than it was for auditory presentation on the longer messages. Repetition of the instructions generally lowered execution performance for longer messages, which required more output, especially with the visual modality, which required phonological receding from visual input to spoken output. An advantage for reduced over full repetition for visual but not for auditory presentation was attributed to an enhanced visual scanning process.