FACTORS INFLUENCING THE APPARENT VELOCITY OF VISUAL MOVEMENT AFTER-EFFECTS

D ureman , I. Factors influencing the apparent velocity of visual movement after-effects. Scand. J. Psychol ., 1962, 3 , 132–136.—Estimates of speed of apparent visual movement after-effects (VMAE) were undertaken with induction speed varied in five logarithmic steps from 9° to 144° per second. Two alternative test intervals 0.5 and 1.0 sec were used for intermittent inspection of a stationary target. At both inspection intervals VMAE-velocity estimates were found to vary in a systematic way with induction speed. Comparing values from the two test intervals, the 0.5 sec interval was found to yield significantly higher speed of VMAE than the 1.0 sec interval.     

About the role of bottom-up and top-down processes on perception–action interaction in sensorimotor transformations

Theories of common-coding propose that feature codes of perceived and to-be-produced events are likely to interact with each other when they overlap. We investigated the impact of bottom-up and top-down processes on cross talk in a motor replication task. Participants moved a pen on a covered digitizer tablet while a gain varied the relation between hand and cursor amplitude. Then, participants replicated the hand amplitude (intra-modal) or the cursor amplitude (intermodal) without visual feedback. We replicated that, when the not-to-be-replicated amplitude was longer (shorter) than the to-be-replicated amplitude, replications significantly overshot (undershot) (= after-effects). Importantly, after-effects were remarkably smaller in the experimental groups which wore gloves (thin and thick rubber) or goggles (clear and tinted lenses) than in a control group. Our results provide evidence that top-down attention modulated perception–action interaction.     

Three- and two-dimensional motion after-effects

Abstract.— The principle of perceptual vector analysis proposed by Johansson (1W) implicitly assumes the organism to be equipped with physiological systems sensitive to common and divergent components of change in the proximal stimulation. The present investigation was designed to study these units by means of the after-effect paradigm. It was found that prolonged viewing of complex changes produced after-effects of motion in depth and changing form specific to the common and divergent components of change in the stimulation. Data supported an explanation of these after-effects in terms of adaptation of units selectively sensitive to different kinds of motion vectors.     

Interocular transfer of visual aftereffects

A number of the well-known visual after-effects of adaptation exhibit interocular transfer, so that presentation of an adaptation figure to one eye produces a temporary change in the performance of the nonadapted eye. This outcome is usually attributed to the involvement of binocular visual neurons that respond to stimulation of either eye. The fact that interocular transfer is incomplete (i.e., the transferred aftereffect is smaller in magnitude than that induced and measured in the same eye) is routinely cited as evidence for the involvement of monocular neurons. This article critically examines these two interpretations, which are developed in terms of a neural model of interocular transfer. No evidence, logical or empirical, was obtained for rejecting the model. Our analysis further shows that the model must assume some type of pooling process that operates over all tested neurons, both adapted and unadapted. Finally, general implications of the interocular transfer model are discussed, the aim being to delimit the conclusions that may be drawn from interocular transfer experiments.     

Application of the sensory-tonic theory of perception to figural after-effect

Current theoretical positions concerned with figural after-effects were criticized for their inadequacy in accounting for figural after-effects data and for their failure to link these phenomena with other perceptual phenomena in any systematic fashion. On the basis of the relative broadness of Gibson's early formulation, it was decided to adapt a similar adaptation theory, the sensory-tonic field theory of perception, to figural after-effect displacements. Appropriate hypotheses were stated and predictions made. These were tested and confirmed. It was concluded that although the success of the theory is limited, there appears to be hope for its extension.     

The after-effects of ventriloquism

Subjects were tested for both ear-hand and eye-hand co-ordination before and after monitoring a synchronous series of noise bursts and of light flashes coming from the same spatial position, but with the virtual position of the flashes displaced 15° laterally by prisms. Attention was forced on both stimuli by the instruction to detect occasional reductions in intensity. No subject reported noticing the spatial discrepancy. Nevertheless ear--hand co-ordination was shifted in the direction of the prismatic displacement, and eye-hand co-ordination in the opposite direction. Both shifts were observed with instructions suggesting that the sound and the light came from one single source, with instructions suggesting two separate sources, and also with no information regarding the spatial relationship of sound and light. It is concluded that the resolution of auditory-visual spatial conflict involves recalibrations of both visual and auditory data and that these alterations last long enough to be detected as after-effects.     

Dichoptic induction of Mccollough-type effects

If left-oblique and right-oblique black/white gratings are presented alternately to one eye, and unpatterned red and green fields are presented alternately to the other, orientation-sensitive chromatic after-effects are induced. With the colour-stimulated eye the hue usually seen on a test grating is complementary to that originally paired with its orientation, with the pattern-stimulated eye the hue is the same as that originally paired.

The experiments reported here show that: (a) the time course of decay of these chromatic after-effects (for each eye) fits approximately the same power law as that found for the normal McCollough effect; (b) analogous chromatic after-effects, opposite in the two eyes, can be dichoptically induced using pairs of stimuli other than gratings, such as dot patterns differing in magnification.

These results suggest that strongly coloured light in one eye can induce a weakly complementary bias in the colour-signalling system of the other eye, at a level peripheral to the site of the McCollough-type adaptation.     

Visuomotor adaptation and its relationship with motor ability in children with and without autism spectrum disorder

The high prevalence rates of motor impairments among individuals with autism spectrum disorder (ASD) lead to increased attention to motor learning. The current study examined the visuomotor adaptability in children with and without ASD using a computerized visuomotor adaptation task in which the real-time visual feedback of hand movement was rotated. The relationships between visuomotor adaptability and clinical symptomology were also investigated. Results revealed that the children with ASD showed a slower rate of improvement and smaller after-effects than their peers on the measures of motor planning. Additionally, autistic characteristics significantly moderated the association between individuals' adaptability and fine motor skills. The findings contribute to the growing evidence of compromised visuomotor adaptability, which suggested the importance of addressing these clinical features of ASD.     

A further investigation of apparent size and retinal size as determinants of the figural after-effect

A figure which is more distant from the eye than another but subtends the same visual angle is usually seen as the larger. This phenomenon is called perceptual size constancy. Experiments have been reported which show that sometimes the apparent and sometimes the retinal sizes of the stimulus figures determine the direction of the figural after-effect. These experiments are reviewed and two further experiments are reported. In the first experiment two types of stimulus figure (discs and annuli) which subtended a visual angle of 1° 36' resulted in figural after-effects, the direction of which would have been predicted by the retinal sizes of the figures. In the second experiment larger figures were used which subtended a visual angle of about 4° and which were the same as those used by Sutherland (1954). In this experiment the after-effects were generally in a direction which would have been expected if apparent size determined the direction of the after-effect. In the interpretation of the results attention is drawn to the “Central Tendency Effect” which has been observed in size judgements of stimulus figures of varying size. Two hypotheses are suggested; one is that the true figural aftereffect has been obscured by the “Central Tendency Effect” in successive judgements, and the other is that time error in successive judgements of size is essentially a figural aftereffect. Some supportive evidence for the latter hypothesis is reported. It is concluded that apparent size is not a critical determinant of the figural after-effect.     

Figural after-effects, retinal size, and apparent size

The results of earlier experiments on the question of whether figural after-effects are affected by apparent as opposed to retinal size are shown to be inconclusive. A new hypothesis is proposed namely that both factors may be responsible for producing figural aftereffects, and four experiments have been made to test it. Situations were used in which the apparent sizes of the figures were determined by the size-constancy effect. It was found that where retinal sizes of test and inspection figures are the same and apparent sizes are different, figural after-effects in the direction which would be predicted on the basis of apparent sizes are obtained. It was further shown that where retinal and apparent sizes are in conflict, whether a figural after-effect is seen or not, and the direction of the figural after-effect, depends upon the balance between these two factors.     

Effects of varying the apparent tilt of the inspection figure on a kinaesthetic after-effect

Three experiments were conducted to determine whether kinaesthetic after-effects, measured by settings of a bar to the horizontal, are controlled by the apparent or the physical tilt of the bar during inspection. Two arrangements were used to induce a discrepancy between apparent and physical tilt. Data obtained with one arrangement did not permit a proper test of the issue. With the other arrangement either distorted or undistorted visual information about tilt was present during kinaesthetic inspection. It was found that post-inspection settings were displaced from pre-inspection settings in the direction of the tilt of the inspection figure when there was no discrepancy between information presented by the two modalities. When there was a discrepancy, the displacements attributable to apparent tilt were in the direction opposite to the apparent tilt of the inspection figure. The former effects dissipated rapidly after inspection; the latter did not. It is suggested that after-effects obtained following an inspection period during which there is no discrepancy between physical and apparent tilt are controlled by the physical tilt of the inspection figure and that apparent tilt, when it is an effective variable, operates by modifying the judgemental frame of reference.     

Adaptation to display rotation and display gain distortions during drawing

The relationship between movement extent and movement direction coding mechanisms was investigated using a visuomotor adaptation paradigm. To determine if these mechanisms are either modular or interdependent, young healthy college students were tested while they performed a visually guided drawing task that incorporated varying combinations of movement distance and direction distortions. Analysis of participants' standardized movement duration, initial directional error, and movement length over the course of the adaptation process revealed a certain degree of interdependence between direction and extent coding mechanisms. Specifically, changes in final adaptation levels and after-effects depended on the order of introduction of the visual distortions. This interaction can be characterized as unidirectional, where alterations in rotational feedback interfere with subsequent adaptation to gain changes, whereas alterations in "display gain" do not significantly impede the adaptation to "display rotation". Moreover, simultaneous exposure to gain and rotational distortions resulted in better learning. The results argue against an independent coding of movement direction and extent during adaptation by the central nervous system.     

Direct-effects and after-effects of dynamic adaptation on intralimb and interlimb transfer

After-effects following sensorimotor adaptation are generally considered as evidence for the formation of an internal model, although evidence lacks on whether the absence of after-effects necessarily indicates that the adaptation did not result in the formation of an internal model. Here, we examined direct- and after-effects of dynamic adaptation with one arm at one workspace on subsequent performance with the other arm, as well as the same arm at another workspace. During training, subjects performed reaching movements under a novel dynamic condition with the right arm; during testing, they performed reaching movements with the left or right arm at a new workspace, under either the same dynamic condition (direct-effects) or a normal condition (after-effects). Results showed significant transfer within the same arm in terms of both direct- and after-effects, but significant transfer across the arms only in terms of direct-effects. These findings suggest that the formation of an internal model does not always result in after-effects. They also support the idea that the neural representation developed after sensorimotor adaptation comprise some aspects that are effector independent and other aspects that are effector dependent; and that direct- and after-effects following sensorimotor adaptation mainly reflect the effector-independent and the effector-dependent aspects, respectively.     

An Associative Interpretation of the Indirect McCollough Effect

Following an induction procedure in which a coloured grid is alternated with a square of a complementary colour, subjects report colour after-effects on both the grid orientation present during induction and the orthogonal non-induced grid orientation. The after-effect reported on the induced grid orientation is called the McCollough effect (ME). The aftereffect reported on the non-induced grid orientation is called the indirect ME. There is evidence that the ME represents an instance of Pavlovian conditioning. The present results support a conditioning interpretation of the indirect ME and are inconsistent with interpretations of the indirect ME that attribute the phenomenon to special orthogonal coding mechanisms within the visual system.     

Eye movements during the production of nouns and pronouns

Earlier research has established that speakers usually fixate the objects they name and that the viewing time for an object depends on the time necessary for object recognition and for the retrieval of its name. In three experiments, speakers produced pronouns and noun phrases to refer to new objects and to objects already known. Speakers looked less frequently and for shorter periods at the objects to be named when they had very recently seen or heard of these objects than when the objects were new. Looking rates were higher and viewing times longer in preparation of noun phrases than in preparation of pronouns. If it is assumed that there is a close relationship between eye gaze and visual attention, these results reveal (1) that speakers allocate less visual attention to given objects than to new ones and (2) that they allocate visual attention both less often and for shorter periods to objects they will refer to by a pronoun than to objects they will name in a full noun phrase. The experiments suggest that linguistic processing benefits, directly or indirectly, from allocation of visual attention to the referent object.     

Effects of situational cues on prism-induced aftereffects

A test was made of the hypothesis that external stimuli present during exposure to lateral displacement of the visual field can serve as situational cues whose presence or absence will influence the magnitude of aftereffects manifested subsequent to adaptation resulting from the exposure. The results indicated that the relative aftereffects were significantly greater when thenondisplacing goggles were worn during the periods in which aftereffect measurements were taken than was the case when they were removed during these test periods. The finding that manipulation of certain cues, i.e., the restriction of the visual field, weight, etc., of the goggles, associated with the adaptation period can in part determine the size of observed aftereffects provides evidence in support of the notion that aftereffects can be conditioned to precisely given constellations of stimuli In addition, the need for caution in conceptualizing aftereffects as simply the persistence of adaptive shifts once visual displacement has been terminated is suggested.     

Top-down knowledge modulates onset capture in a feedforward manner

How do we select behaviourally important information from cluttered visual environments? Previous research has shown that both top-down, goal-driven factors and bottom-up, stimulus-driven factors determine which stimuli are selected. However, it is still debated when top-down processes modulate visual selection. According to a feedforward account, top-down processes modulate visual processing even before the appearance of any stimuli, whereas others claim that top-down processes modulate visual selection only at a late stage, via feedback processing. In line with such a dual stage account, some studies found that eye movements to an irrelevant onset distractor are not modulated by its similarity to the target stimulus, especially when eye movements are launched early (within 150-ms post stimulus onset). However, in these studies the target transiently changed colour due to a colour after-effect that occurred during premasking, and the time course analyses were incomplete. The present study tested the feedforward account against the dual stage account in two eye tracking experiments, with and without colour after-effects (Exp. 1), as well when the target colour varied randomly and observers were informed of the target colour with a word cue (Exp. 2). The results showed that top-down processes modulated the earliest eye movements to the onset distractors (<150-ms latencies), without incurring any costs for selection of target matching distractors. These results unambiguously support a feedforward account of top-down modulation.     

APPARENT SIZE AS A DETERMINER OF FIGURAL AFTER-EFFECTS. I

K olehmainen , K. Apparent size as a determiner of figural after-effects. I. Scand. J. Psychol ., 1968, 9, 230–236.—Apparent size as a determiner of figural after-effects (FAE) was studied by presenting the inspection figures in drawings which appeared three-dimensional because of gradient-effects. Significant FAEs were found. It is argued that apparent size does not determine FAE directly but an apparent decrement in the size of the test figure is connected to an after-effect in third-dimension.     

Steady happiness on a wheel-chair. Denial,masochism or after-effects of a near-death experience?

The author describes his weird affective condition of steady happiness, after a severe haemorrhagic stroke, that brought to a sudden stop of all his professional activities and caused multiple severe motoric symptoms. The author suggests that his affective state, wholly different from his baseline condition before the stroke, is very close to what is reported by survivors of near-death experience (NDE), as long-time after-effects of the experience. Therefore, it is suggested that the psychoanalyst, in confronting with weird conditions of well-being, should consider the possibility of after-effects of an NDE, alongside with the operation of primitive defences.     

The direction of masked auditory category priming correlates with participants' prime discrimination ability

Semantic priming refers to the phenomenon that participants typically respond faster to targets following semantically related primes as compared to semantically unrelated primes. In contrast, Wentura and Frings (2005) found a negatively signed priming effect (i.e., faster responses to semantically unrelated as compared to semantically related targets) when they used (a) a special masking technique for the primes and (b) categorically related prime-target-pairs (e.g., fruit-apple). The negatively signed priming effect was most pronounced for participants with random prime discrimination performance, whereas participants with high prime discrimination performance showed a positive effect. In the present study we analyzed the after-effects of masked category primes in audition. A comparable pattern of results as in the visual modality emerged: The poorer the individual prime discrimination, the more negative is the semantic priming effect. This result is interpreted as evidence for a common mechanism causing the semantic priming effect in vision as well as in audition instead of a perceptual mechanism only working in the visual domain.