Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perceptual Distortion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed1976

The components of the Poggendorff illusion.

An explanation of the Poggendorff misalignment illusion in terms of three basic components, the horizontal-vertical, longitudinal-transverse and obtuse angle effects, is proposed. It is argued that these effects amy either singly or jointly give rise to an apparent elongation- contraction of the space between the aligned elements with consequent change in apparent oblique direction. Experimental evidence for the involvement of the three components in various combinations and for modification of perceived direction between the transversals is presented. It is shown that the illusion in various forms of the Poggendorff figure can be accounted for by the involvement of one or more of the three components, each of which can be demonstrated independently of the illusion. It is suggested that other classical illusions, including the Müller-Lyer, might also be analysed in terms of basic components.

Humans↗
PubMed1996

Methodological issues in assessment of the perceptual component of body image disturbance.

An individual's body image consists of both a perceptual and an attitudinal (subjective) component. Methodological issues relative to the measurement of the perceptual component of body image are discussed. Traditionally, research in body image has employed psychophysical techniques and analyses which confound these two components. Psychophysical techniques which allow for a separate measurement of these two components are discussed, including method of constant stimuli, signal detection theory and adaptive probit estimation. The results of research utilizing these techniques are described and the importance of separately measuring perceptual and attitudinal components is discussed.

Adult↗
PubMed1977

Psychogenic vertigo within an anxiety frame of reference: an experimental study.

The theoretical point of departure here was the assumption that a psychogenic vertigo patient displaces affect, or experience of anxiety to one of dizziness, the dizziness serving as an anxiety equivalent. This is seen to imply a change in the locus of experience from the me to the not-me sphere. "Percept-genetic" techniques and a spiral after-effect measurement were used to compare 23 patients with presumed psychogenic vertigo with a control group matched in sex, age, education and occupation. Results of the percept-genetic techniques showed the patients to display stronger signs of affect anxiety than subjects in the control group. Also two main subgroups of patients were differentiated with the help of the descriptive instruments, one group with signs of a primitive-hysteroid mode of functioning, the other with signs of an obsessive-compulsive mode. For both subgroups the suggested displacement mechanism seemed to be functioning. Its apparent effect differed, however, for the two subgroups: in the "primitive-hysteroid" group the displacement mechanism was more effective. The "obsessive-compulsive" group showed stronger signs of affect anxiety, dizziness here being better characterized as a concomitant than as an equivalent of anxiety. Results of a follow-up two years after the investigation also showed a poorer development of symptoms within the "obsessive-compulsive" group.

Adult↗
PubMed1982

Body image: a selective review of existing measurement techniques.

A selective review of studies concerning body image is presented to illustrate the diversity of approaches which have been adopted. Equivocal definitions of the concept of body image and the difficulties inherent in its measurement are examined and the most popular measurement techniques are described and criticized.

Body Image↗
PubMed1998

Subjective body-image dimensions in normal and anorexic adolescents.

The subjective body dimensions of adolescent anorexic patients and adolescents from the general population were studied by means of a new technique that combines certain characteristics of the 'body-site estimation' and the 'whole-image adjustment' procedures. The technique used (Subjective Body Dimensions Apparatus-SBDA) reveals the individual's idea of the size of the different parts of his/her body, and produces a life-size global silhouette. Eighty-five female anorexic patients (ages 12 to 18) were compared with 427 adolescents from the general population. The technique showed acceptable test-retest stability. The comparison group overestimated their thorax, waist and hips, and anorexic patients overestimated all parts of their body but their thorax, waist and hips especially. For all parts of the body, the anorexic group showed greater overestimation (p < .0001) than the comparison group.

Adolescent↗
PubMed1972

Physiological correlates of adaptation to a rotated visual field.

1. Perceptual adaptation to a 30 or 45 degrees visual tilt was induced in human subjects by means of prismatic spectacles worn for 5-7 days. Relative contrast thresholds and the amplitudes of the occipital potentials to vertical and oblique gratings were studied.2. During continuous exposure to the tilted visual environment the normal differences between contrast thresholds for vertical and oblique targets decreased or were no longer significant. In all subjects the change from control threshold differences was significant at the 0.005 level.3. During the course of adaptation the difference in amplitude of the potentials evoked by vertical and oblique oscillating gratings also decreased. The changes with respect to control differences were significant at the 0.005 level in each subject.4. Intermittent exposure to tilt in one subject resulted only in minor adaptation of the apparent vertical, and the evoked potential differences did not change from control levels.5. The changes are interpreted as suggesting that plastic changes in the extraretinal mechanism responsive to target orientation occur during adaptation to prismatic tilt.

Adaptation, Ocular↗
PubMed2003

Control of voice fundamental frequency in speaking versus singing.

In order to investigate control of voice fundamental frequency (F0) in speaking and singing, 24 adults had to utter the nonsense word ['ta:tatas] repeatedly, while in selected trials their auditory feedback was frequency-shifted by 100 cents downwards. In the speaking condition the target speech rate and prosodic pattern were indicated by a rhythmic sequence made of white noise. In the singing condition the sequence consisted of piano notes, and subjects were instructed to match the pitch of the notes. In both conditions a response in voice F0 begins with a latency of about 150 ms. As predicted, response magnitude is greater in the singing condition (66 cents) than in the speaking condition (47 cents). Furthermore the singing condition seems to prolong the after-effect which is a continuation of the response in trials after the frequency shift. In the singing condition, response magnitude and the ability to match the target F0 correlate significantly. Results support the view that in speaking voice F0 is monitored mainly supra-segmentally and controlled less tightly than in singing.

Adult↗
PubMed2004

A numerical study of the role of the tragus in the big brown bat.

A comprehensive characterization of the spatial sensitivity of an outer ear from a big brown bat (Eptesicus fuscus) has been obtained using numerical methods and visualization techniques. Pinna shape information was acquired through x-ray microtomography. It was used to set up a finite-element model of diffraction from which directivities were predicted by virtue of forward wave-field projections based on a Kirchhoff integral formulation. Digital shape manipulation was used to study the role of the tragus in detailed numerical experiments. The relative position between tragus and pinna aperture was found to control the strength of an extensive asymmetric sidelobe which points in a frequency-dependent direction. An upright tragus position resulted in the strongest sidelobe sensitivity. Using a bootstrap validation paradigm, the results were found to be robust against small perturbations of the finite-element mesh boundaries. Furthermore, it was established that a major aspect of the tragus effect (position dependence) can be studied in a simple shape model, an obliquely truncated horn augmented by a flap representing the tragus. In the simulated wave field around the outer-ear structure, strong correlates of the tragus rotation were identified, which provide a direct link to the underlying physical mechanism.

Animals↗
PubMed2005

Perceptual compensation for effects of reverberation in speech identification.

Listeners were asked to identify modified recordings of the words "sir" and "stir," which were spoken by an adult male British-English speaker. Steps along a continuum between the words were obtained by a pointwise interpolation of their temporal-envelopes. These test words were embedded in a longer "context" utterance, and played with different amounts of reverberation. Increasing only the test-word's reverberation shifts the listener's category boundary so that more "sir"-identifications are made. This effect reduces when the context's reverberation is also increased, indicating perceptual compensation that is informed by the context. Experiment 1 finds that compensation is more prominent in rapid speech, that it varies between rooms, that it is more prominent when the test-word's reverberation is high, and that it increases with the context's reverberation. Further experiments show that compensation persists when the room is switched between the context and the test word, when presentation is monaural, and when the context is reversed. However, compensation reduces when the context's reverberation pattern is reversed, as well as when noise-versions of the context are used. "Tails" that reverberation introduces at the ends of sounds and at spectral transitions may inform the compensation mechanism about the amount of reflected sound in the signal.

Adaptation, Physiological↗
PubMed1983

Discrimination of speech processed by low-pass filtering and pitch-invariant frequency lowering.

Consonant discriminability by normal-hearing listeners was studied for monosyllables processed using frequency lowering with either uniform (linear) or nonuniform (warped) compression of the frequency axis. The bandwidth of the compressed signal was either 2500 or 1250 Hz and five compression characteristics were studied, in addition to low-pass filtering, for each of the two bandwidths. Stimuli were 24 consonant-vowel syllables made up of 24 consonants and three vowels, recorded three times by each of two male and female speakers. A "roving-speaker, roving-vowel, roving-utterance," two-interval, forced-choiced procedure with feedback was employed. As expected, performance for the 2500-Hz bandwidth was superior to that for the 1250-Hz bandwidth. For each bandwidth, compression schemes which accomplished greater lowering of the high frequencies relative to the low frequencies resulted in the highest performance. Overall performance for the best frequency-lowering system studied, however, was roughly comparable to that obtained for low-pass filtering. Patterns of performance over articulatory features were different for frequency lowering and filtering. In general, lowering was superior to filtering for contrasts of fricative sounds but inferior for contrasts of nasals and semivowels.

Female↗
PubMed1985

Acoustic emissions from the ear: a summary of results from humans and animals.

As mentioned in Saunders et al. [J. Acoust. Soc. Am. 78, 299-311 (1985)] an understanding of the transduction of sound into the auditory neural code is a major goal of the hearing scientist. A variety of tools has been and is being used to achieve that goal. The recent discovery of physical acoustic emissions from the ear provides both new insight into possible transduction mechanisms and a useful new tool for research. The existence of narrow-band spontaneous acoustic emissions from the ear suggests the possibility of active cochlear processes that were not seriously considered a decade ago. Acoustic emissions, both spontaneous and evoked, also provide a simple and noninvasive means of monitoring a by-product of cochlear-mechanical activity. In the present paper, results of studies of acoustic emissions from human ears are briefly summarized and compared to results obtained with animals. Differences between human and animal emissions are noted and the implications of these differences and hypotheses to explain them are discussed.

Animals↗
PubMed1990

Effects of electrical polarization on inner hair cell receptor potentials.

Ac and dc receptor potential components in response to tone-burst stimuli were measured from inner hair cells in the third cochlear turn of the guinea pig. Comparisons were sought between conditions when constant polarizing current was injected into the cell through the recording electrode and when there was no extrinsic current. Hyperpolarization of the cell increased all responses, while depolarization decreased them. The input-output functions were vertically translated by current injection. The extent of translation was a function of current level. In addition, the amount of current-induced change was frequency dependent. Largest changes were seen at low frequencies and the current-induced change tended toward a constant high-frequency asymptote between 1-2 kHz. Changes in the dc response component were considerably in excess of those for the fundamental ac response. The frequency-dependent effects are quantified with the aid of a hair cell circuit model [P. Dallos, Hear. Res. 14, 281-291 (1984)]. It is assumed that the quantity altered by polarizing current (actually by the transmembrane voltage) is the resistance of the cell's basolateral membrane.

Animals↗
PubMed1990

Perceptual linear predictive (PLP) analysis of speech.

A new technique for the analysis of speech, the perceptual linear predictive (PLP) technique, is presented and examined. This technique uses three concepts from the psychophysics of hearing to derive an estimate of the auditory spectrum: (1) the critical-band spectral resolution, (2) the equal-loudness curve, and (3) the intensity-loudness power law. The auditory spectrum is then approximated by an autoregressive all-pole model. A 5th-order all-pole model is effective in suppressing speaker-dependent details of the auditory spectrum. In comparison with conventional linear predictive (LP) analysis, PLP analysis is more consistent with human hearing. The effective second formant F2' and the 3.5-Bark spectral-peak integration theories of vowel perception are well accounted for. PLP analysis is computationally efficient and yields a low-dimensional representation of speech. These properties are found to be useful in speaker-independent automatic-speech recognition.

Adult↗