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Biomedical subjects

M Kubovy

Publications and source records attributed to M Kubovy.

15 recordsLinked to original sources
PubMed2001

Auditory and visual objects.

Notions of objecthood have traditionally been cast in visuocentric terminology. As a result, theories of auditory and cross-modal perception have focused more on the differences between modalities than on the similarities. In this paper we re-examine the concept of an object in a way that overcomes the limitations of the traditional perspective. We propose a new, cross-modal conception of objecthood which focuses on the similarities between modalities instead of the differences. Further, we propose that the auditory system might consist of two parallel streams of processing (the 'what' and 'where' subsystems) in a manner analogous to current conceptions of the visual system. We suggest that the 'what' subsystems in each modality are concerned with objecthood. Finally, we present evidence for - and elaborate on - the hypothesis that the auditory 'where' subsystem is in the service of the visual-motor 'where' subsystem.

Auditory Perception↗
PubMed2001

Internalization: a metaphor we can live without.

Shepard has supposed that the mind is stocked with innate knowledge of the world and that this knowledge figures prominently in the way we see the world. According to him, this internal knowledge is the legacy of a process of internalization; a process of natural selection over the evolutionary history of the species. Shepard has developed his proposal most fully in his analysis of the relation between kinematic geometry and the shape of the motion path in apparent motion displays. We argue that Shepard has made a case for applying the principles of kinematic geometry to the perception of motion, but that he has not made the case for injecting these principles into the mind of the percipient. We offer a more modest interpretation of his important findings: that kinematic geometry may be a model of apparent motion. Inasmuch as our recommended interpretation does not lodge geometry in the mind of the percipient, the motivation of positing internalization, a process that moves kinematic geometry into the mind, is obviated. In our conclusion, we suggest that cognitive psychologists, in their embrace of internal mental universals and internalization may have been seduced by the siren call of metaphor.

Biomechanical Phenomena↗
PubMed2000

The emergence of visual objects in space-time.

It is natural to think that in perceiving dynamic scenes, vision takes a series of snapshots. Motion perception can ensue when the snapshots are different. The snapshot metaphor suggests two questions: (i) How does the visual system put together elements within each snapshot to form objects? This is the spatial grouping problem. (ii) When the snapshots are different, how does the visual system know which element in one snapshot corresponds to which element in the next? This is the temporal grouping problem. The snapshot metaphor is a caricature of the dominant model in the field-the sequential model-according to which spatial and temporal grouping are independent. The model we propose here is an interactive model, according to which the two grouping mechanisms are not separable. Currently, the experiments that support the interactive model are not conclusive because they use stimuli that are excessively specialized. To overcome this weakness, we created a new type of stimulus-spatiotemporal dot lattices-which allow us to independently manipulate the strength of spatial and temporal groupings. For these stimuli, sequential models make one fundamental assumption: if the spatial configuration of the stimulus remains constant, the perception of spatial grouping cannot be affected by manipulations of the temporal configuration of the stimulus. Our data are inconsistent with this assumption.

Humans↗
PubMed1999

Weakening the robustness of perspective: evidence for a modified theory of compensation in picture perception.

Viewed from the center of projection, a perspective picture presents the pictorial depth information of a scene. Knowing the center of projection, one can reconstruct the depicted scene. Assuming another viewpoint is the center of projection will cause one to reconstruct a transformed scene. Despite these transformations, we appreciate pictures from other viewpoints. The compensation hypothesis states that the visible picture surface allows observers to compensate for transformations by locating the center of projection and experiencing pictorial space from there. We show that observers neither completely compensate for nor experience transformations of space as geometry would predict. We propose a modified compensation hypothesis according to which different degrees of visibility of the picture surface invoke different degrees of compensation.

Female↗
PubMed1998

On the lawfulness of grouping by proximity.

The visual system groups close things together. Previous studies of grouping by proximity have failed to measure grouping strength or to assess the effect of configuration. We do both. We reanalyze data from an experiment by Kubovy and Wagemans (1995) in which they briefly presented multi-stable dot patterns that can be perceptually organized into alternative collections of parallel strips of dots, and in which they parametrically varied the distances between dots and the angles between alternative organizations. Our analysis shows that relative strength of grouping into strips of dots of a particular orientation approximates a decreasing exponential function of the relative distance between dots in that orientation. The configural or wholistic properties that were varied--such as angular separations of the alternative organizations and the symmetry properties of the dot pattern--do not matter. Additionally, this grouping function is robust under transformations of scale in space (Experiment 1) and time (Experiment 2). Grouping of units which are themselves the result of grouping (i.e., pairs of dots; Experiment 3) also follows our nonconfigural rule.

Adult↗
PubMed1997

Detection of symmetry and perceptual organization: the way a lock-and-key process works.

We studied the speed with which observers could detect symmetry in drawings that incorporated symmetric contours--related by reflection or translation--within single objects or across different objects. We asked observers to perform a speeded decision whether pairs of contours are the same, i.e., related by reflection or by translation, or different. When the contours belong to a single object, observers are faster to see the relation between contours when they are related by reflection than by translation. When the contours belong to different objects, observers are faster to see the relation between the contours when they are related by translation than by reflection. We tested whether this advantage of translation is due to a lock-and-key process. We first tested our hypothesis by manipulating the correspondence of the features, so as to make matching more difficult. This change did not produce the predicted pattern of results. We performed a second manipulation to change the appearance of the objects: we increased the prägnanz of the objects by changing the type of lines used to connect the contours. Results indicate that perceptual organization can alter detectability of symmetry.

Female↗
PubMed1993

Mental rotation, mental representation, and flat slopes.

The "mental rotation" literature has studied how subjects determine whether two stimuli that differ in orientation have the same handedness. This literature implies that subjects perform the task by imagining the rotation of one of the stimuli to the orientation of the other. This literature has spawned several theories of mental representation. These theories imply that mental representations cannot be both orientation-free and handedness-specific. We present four experiments that demonstrate the contrary: mental representations can be both orientation-free and handedness-specific. In Experiment 1 we serendipitously discovered a version of R. N. Shepard and J. Metzler's (1971) "mental rotation" task in which subjects accurately discover the handedness of a stimulus without using "mental rotation," i.e., in which reaction time to compare the handedness of two forms is not a function of the angular disparity between the two forms. In Experiment 2 we generalize this finding to different experimental procedures. In Experiment 3 we replicate this finding with a much larger group of subjects. In Experiment 4 we show that when we preclude the formation of an orientation-free representation by never repeating a polygon, subjects carry out the handedness comparison task by performing "mental rotation."

Adult↗
PubMed1992

Caricature and face recognition.

Although caricatures are often gross distortions of faces, they frequently appear to be super-portraits capable of eliciting recognition better than veridical depictions. This may occur because faces are encoded as distinctive feature deviations from a prototype. The exaggeration of these deviations in a caricature may enhance recognition because it emphasizes the features of the face that are encoded. In two experiments, we tested the superportrait hypothesis and the encoding-by-caricature hypothesis. In the first experiment, caricatures were recognized better than faces, and true caricatures of previously seen faces were recognized better than the faces from which the caricatures had been developed. In the second experiment, faces and their caricatures were tachistoscopically presented in a sequential same/different reaction time task. Subjects were slower to distinguish the stimuli when the face preceded its caricature, indicating that caricatures are more similar to the encoded representation of a face than are stimuli in which the distinctive features are deemphasized.

Adult↗
PubMed1979

Tone-segregation by phase: on the phase sensitivity of the single ear.

A monaural complex tone is synthesized from 12 harmonically related pure tones, played in phase. In each of 12 segments, one of the tones (the target) is played out of phase so that the sequence of targets is increasing or decreasing in frequency. If the target is at least 30 degrees out of phase, the targets are perceptually segregated. This tone-segregation by phase raises doubts concerning several current theories of pitch perception. The phenomenon is conjectured to be caused by the ear's nonlinear compressive transfer characteristic or by a temporal analysis of the stimulus.

Acoustic Stimulation↗
PubMed1976

Persistence of a pitch-segregating echoic memory.

Auditory stimuli were computer generated in order to measure the persistence of echoic memory. The stimuli consisted of 18 bursts (lasting 307 msec) of six equal-amplitued dichotic tones (frequencies: 392, 440, 494, 523, 587, and 659 Hz), each having a different interaural time disparity. For each stimulus a canonical distribution of interaural time disparities was defined. Five of the interaural time disparities in each burst were equal to canonical disparities for that stimulus; the sixth was not. The deviant tones in successive bursts constituted a musical scale. These deviant tones were perceptually segregated when the interburst interval was short, even though individual bursts sounded like noise when played separately. The interburst intervals for which five subjects could identify with 71% accuracy whether the scale was ascending or descending (obtained by an adaptive psychophysical procedure) averaged about 1 sec. This figure represents a lower bound on the average half-life of echoic memory. A sixth subject performed perfectly even with an inter burst interval of 9.7 sec. Two further experiments were carried out with this subject to support the claim that his performance was due to echoic memory.

Acoustic Stimulation↗
PubMed1974

Hearing with the third ear: dichotic perception of a melody without monaural familiarity cues.

Julesz has shown that cross-correlations between two patterns that appear random to either eye alone can give rise to the perception of form and depth when viewed stereoscopically. We produced auditory analogs by presenting eight simultaneous and continuous sine waves to both ears and by either phaseshifting or frequency-shifting one of them relative to its counterpart in the opposite ear. Particular tones were shifted in sequence such that a melody was heard which was undetectable by either ear alone.

Acoustic Stimulation↗