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Biomedical subjects

S Mateeff

Publications and source records attributed to S Mateeff.

At least 37 records · Page 2Linked to original sources
PubMed1988

Perceptual latencies are shorter for motion towards the fovea than for motion away.

Subjects had to align a brief test flash with a peripheral steady reference target during ocular pursuit, or with a moving reference target during steady eye fixation. The performance was determined by the direction of movement, of the reference target image on the retina--towards or away from fovea. The data are explained by the hypothesis that the passage of a retinal locus by a moving target image is experienced faster when the image moves foveopetally, regardless of whether the passage is caused by real target movement or by ocular pursuit.

Adult↗
PubMed1988

Dynamic auditory localization: perceived position of a moving sound source.

Experiments are presented in which a sound source was moved at 15.2 cm/s over a horizontal path of 60 cm length, positioned at a 57 cm distance in front of the observer, symmetrically relative to the median plane. The subjects had to localize the sound at different moments of time. The sound source was predominantly mislocated in the direction of the movement; the mislocation increased at the end of the movement by up to 10-11 deg. In another condition the sound source was localized when it was stationary. In this case the mislocation was directed towards the median plane. The differences between the static and dynamic auditory localization are discussed.

Auditory Perception↗
PubMed1985

Dynamic visual capture: apparent auditory motion induced by a moving visual target.

Apparent motion of a sound source can be induced by a moving visual target. The direction of the perceived motion of the sound source is the same as that of the visual target, but the subjective velocity of the sound source is 25-50% of that of the visual target measured under the same conditions. Eye tracking of the light target tends to enhance the apparent motion of the sound, but is not a prerequisite for its occurrence. The findings are discussed in connection with the 'visual capture' or 'ventriloquism' effect.

Adult↗
PubMed1984

Brief stimuli localization in visual periphery.

Experiments were carried out to establish the effect of stimulus eccentricity and the kind of reference structure on the localization of brief stimuli in the visual periphery. In Experiment 1 the effect of eccentricities up to 55 degrees to the left and to the right of the fixation point on stimulus localization was studied. Systematic errors were obtained, the stimuli being mislocated nearer the fixation point than they were actually presented. The angular size of errors increased with the increase of stimulus eccentricity. In Experiment 2 the subjects had to localize the stimuli against three different background structures (scales). The results showed that error magnitude decreased when scales with clearly visible cues were used. The possible involvement of stimulus direction perception and of the identification of the scale element nearest to the perceived event is discussed.

Adult↗
PubMed1983

Peripheral vision and perceived visual direction.

Experiments are described in which the subjects had to localize brief light stimuli presented up to 10 degrees from the fixation center. The localization was performed relative to a continuously illuminated scale with numbered or lettered divisions. Systematic errors were obtained, the stimuli being mislocated nearer the fixation point than they were actually presented. The angular size of errors increased with the increase of stimulus eccentricity. It appeared to be a characteristic of the stimulated retinal locus, independent of the viewing distance and the scale element corresponding to this locus. It is concluded that despite the presence of a visible background frame of reference, subjects prefer to base their reports on the perceived egocentric direction of the stimulus which does not coincide with the physical direction of the stimulus. A parallel is drawn between this study and the studies on serial position function for letter identification.

Cybernetics↗
PubMed1982

Visual localization during eye tracking on steady background and during steady fixation on moving background.

Experiments were performed to clarify the role of the background motion on the retina in the phenomenon of mislocation of brief visual stimuli during smooth eye tracking. It was found that these visual stimuli were mislocated also relative to a moving background during steady eye fixation. The magnitude of mislocation during pursuit eye movements and during steady fixation was influenced by the stimulus intensity, the background/eye velocity and the place of stimulus presentation in respect to the background; the influence having the same features in both cases. However, the magnitudes of mislocation under the two conditions were quantitatively different. The validity of a hypothesis that the eye movement itself plays no role in the process of localization, and, that this process is based on retinal information only, is considered.

Adult↗
PubMed1981

Localization of brief visual stimuli during pursuit eye movements.

Experimental findings concerning the properties of the phenomenon of mislocation of brief visual stimuli during smooth eye tracking are described. One of these, which cannot be explained by existing hypotheses, is that under certain conditions the mislocation magnitude tends to have zero or even negative values. A model is developed for explanation of the mislocation phenomenon. It is suggested that localization is based on: (1) information about the current eye position and (2) information about the stimulus locus on the retina. They both arrive at the localization centre with non-zero delays. The mode of information processing in this centre leads to a magnitude of mislocation which is proportional to the difference between the two delays and which could be positive, zero or negative. Factors which influence either delay should also influence the mislocation magnitude.

Discrimination, Psychological↗
PubMed1981

Localization of brief light stimuli on differently labelled reference patterns during smooth eye tracking.

Experiments are reported in which the mislocation of brief visual stimuli during tracking eye movements was measured in respect to three kinds of reference patterns placed in the horizontal plane--A) a scale with numbered divisions, B) a bar consisting of seven differently hatched regions; and C) two single markings, the distance between them being equal to the length of patterns A and B. A mislocation of a magnitude up to 2 degrees was obtained in all experiments. The mislocation on reference patterns A and C was the same, the presence of numbered markings did not influence it. The mislocation magnitude tended to decrease when reference pattern B was applied. Conclusion was made that clearly labelled structures near the place of stimulus presentation were a visual cue which affects localization; a scale with identical numbered markings, despite their proximity to the test stimulus, was not a structure of this type.

Eye Movements↗
PubMed1980

Visual perception of movement patterns during smooth eye tracking.

A visual stimulus moving with constant velocity at a definite angle to the horizontal was presented during a 6.5% horizontal pursuit eye movement. The subjects were asked to report the direction of the stimulus movement under conditions of total darkness and on illuminated structured background. In both cases the subject's reports corresponded to the trajectory of the stimulus image on the retina rather than to the physical movement. In a second experiment the subjects were asked to localize the start and the end point of the stimulus motion on illuminated background. In this case the reports corresponded to the physical trajectory of the stimulus motion on the screen. The influence of the visual task on the perception of movement patterns during eye tracking is discussed.

Adaptation, Ocular↗
PubMed1980

Localization of the start and the end point of a moving stimulus path during eye tracking.

The subjects track visually a smoothly moving light target which increases its brightness at a definite point in the visual field and after traversing a path with a definite length, again decreases its brightness to the initial level. The subjects' task is to localize the start and the end point of this path. Systematic misperceptions are observed in the performance of the task, influenced by the position of the stimulus in the visual field and by the length of the path. The mislocation of the end point of the stimulus path is algebraically smaller than the mislocation of the start point. The data are not in agreement with the hypothesis that the visual system first determines the path length and then determines the path position as a whole. The most probable assumption is accepted to be that the processes of localization of the start and the end point of the path are not independent.

Adult↗
PubMed1979

Localization of the change in intensity of a visually pursued light target.

The aim of the subjects was to track a moving light target and to locate the change in its intensity (its disappearance or dimming). It is shown experimentally that: (1) mislocation of target disappearance is smaller than mislocation when the target is dimmed three times; (2) the distance at which the eyes move after the target is darkened does not influence localization. The data disprove possible influence of "overtracking" on localization. They are in favour of the hypothesis about the dependence of localization on stimulus intensity.

Adult↗
PubMed1977

Localization of the disappearance of a light target during tracking eye movements. II.

A light target moving with constant velocity and disappearing at a place determined by the experimenter, is presented to the subjects who track it visually and determine the locus of its disappearance with respect to a scale mounted on the screen. The result is that the disappearance of the target is systematically mislocated in the direction of the eye movement. The value of the mislocation depends on the target intensity. Under different experimental conditions the subjects localize target disappearance by steady fixation of the eyes. The resulting mislocation has entirely different characteristics compared with the first conditions. The theory that the phenomenon of mislocation is due only to wgnal latency in the visual pathways is rejected. A hypothesis is proposed concerning the participation of psychological factors in the process of localization.

Eye Movements↗
PubMed1977

Visual extrapolation of a line segment to the point of its intersection with a straight line. II.

The article describes three experiments to study visual extrapolation of a line segment to the point of its intersection with a straight line. Eye movements are shown to play no significant role in solving problems involving visual spatial extrapolation. It is also indicated that systematic mislocations of the point of intersection sought in cases of acute angles are preserved even when the motor response is substituted by verbal estimation. When the test line segment is presented for a very short time (tau =20 ms), the estimations of the subjects manifest great individual differences and considerable dispersion. The results of the experiments show that the ability of visual extrapolation is influenced by different and numerous factors and this ability does not reflect only the functioning of simple detectors for direction in the visual system.

Adult↗