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Biomedical subjects

P Iverson

Publications and source records attributed to P Iverson.

12 recordsLinked to original sources
PubMed1999

Measuring the perceptual magnet effect in the perception of /i/ by German listeners.

In a study of the internal category structure of the vowel /i/, Kuhl found a "perceptual magnet effect": Discrimination sensitivity was poorer for category instances that were acoustically similar to the category prototype than it was for category instances that were not. The typicality of category exemplars was determined by goodness judgments and was found to correlate with the acoustics of average production. Analysis and interpretation of discrimination performance relied on two important assumptions: that listeners perceived all stimuli presented as exemplars of the same vowel category and that, apart from the influence of phonetic coding, discrimination sensitivity was the same across the investigated part of the vowel space. In the present study, it is shown that production and perception estimates of the category prototype may diverge, possibly because listeners seem to prefer hyperarticulated variants of vowel categories. An approach towards measurement of intra-category discrimination minima is put forward and tested that protects against intercategory confounds and avoids the isosensitivity assumption.

Germany↗
PubMed1999

Name that tune: identifying popular recordings from brief excerpts.

We tested listeners' ability to identify brief excerpts from popular recordings. Listeners were required to match 200- or 100-msec excerpts with the song titles and artists. Performance was well above chance levels for 200-msec excerpts and poorer but still better than chance for 100-msec excerpts. Performance fell to chance levels when dynamic (time-varying) information was disrupted by playing the 100-msec excerpts backward and when high-frequency information was omitted from the 100-msec excerpts; performance was unaffected by the removal of low-frequency information. In sum, successful identification required the presence of dynamic, high-frequency spectral information.

Adult↗
PubMed1999

Prostate cancer in Denmark. Incidence, morbidity and mortality.

Prostate cancer incidence and mortality rates in Denmark are reviewed for a 50-year period from 1943 to 1992. The prostate cancer incidence rate nearly tripled and prostate cancer mortality rate increased during this period. Until recently in Denmark the routine management of prostate cancer has been by deferred hormonal therapy. Morbidity and mortality associated with prostate cancer are analysed in a group of 1459 patients aged 55-74 years, who were diagnosed as having clinically localized prostate cancer in the 5-year period 1983 to 1987. In this group of patients prostate cancer is demonstrated to cause significant morbidity. Furthermore, the patients suffered significant excess mortality and loss of life expectancy.

Aged↗
PubMed1998

[Use of prostate specific antigen. A review].

Since it was first introduced, measurement of prostate specific antigen has gained increasing interest, and prostate specific antigen is regarded as being the best tumour marker available. The antigen lacks cancer specificity, limiting the usefulness in early diagnosis, The use of prostate specific antigen in early diagnosis, staging, and in monitoring patients with prostate cancer is reviewed.

Biomarkers, Tumor↗
PubMed1996

Influences of phonetic identification and category goodness on American listeners' perception of /r/ and /l/.

Recent experiments have demonstrated that category goodness influences the perception of vowels [Iverson and Kuhl, J. Acoust. Soc. Am. 97, 553-562 (1995)]; listeners show a perceptual magnet effect characterized by shrunken perceptual distances near excellent exemplars of vowel categories and stretched distances near poor exemplars. The present study extends this investigation by examining the relative influence of phonetic identification and category goodness on the perception of American English /r/ and /l/. Eighteen /ra/ and /la/ tokens were synthesized by varying F2 and F3 frequencies. Adult listeners identified and rated the goodness of individual stimuli, and rated the similarity of stimulus pairs. Multidimensional scaling analyses revealed that the perceptual space was shrunk near the best exemplars of each category and stretched near the category boundary. In addition, individual differences in /r/ identification corresponded to the degree of shrinking near the best exemplars of the /r/ category. The results demonstrate that category goodness and phonetic identification both contribute to the perception of /r/ and /l/.

Humans↗
PubMed1995

Auditory stream segregation by musical timbre: effects of static and dynamic acoustic attributes.

Two experiments examined the influence of timbre on auditory stream segregation. In experiment 1, listeners heard sequences of orchestral tones equated for pitch and loudness, and they rated how strongly the instruments segregated. Multidimensional scaling analyses of these ratings revealed that segregation was based on the static and dynamic acoustic attributes that influenced similarity judgements in a previous experiment (P Iverson & CL Krumhansl, 1993). In Experiment 2, listeners heard interleaved melodies and tried to recognize the melodies played by a target timbre. The results extended the findings of Experiment 1 to tones varying pitch. Auditory stream segregation appears to be influenced by gross differences in static spectra and by dynamic attributes, including attack duration and spectral flux. These findings support a gestalt explanation of stream segregation and provide evidence against peripheral channel model.

Acoustics↗
PubMed1995

Mapping the perceptual magnet effect for speech using signal detection theory and multidimensional scaling.

Recent experiments have demonstrated that the category goodness of speech sounds strongly influences perception in both adult and infants [Kuhl, Percept. Psychophys. 50, 93-107 (1991); Kuhl et al., Science 255, 606-608 (1992)]. Stimuli judged as exceptionally good instances of phonetic categories (prototypes) make neighboring tokens in the vowel space seem more similar, exhibiting a perceptual magnet effect. Three experiments further examined the perceptual magnet effect in adults. Experiment 1 collected goodness and identification judgments for 13 variants of the vowel /i/. Experiment 2 used signal detection theory to assess the discrimination of these tokens using a bias-free measure (d'). Experiment 3 employed multidimensional scaling (MDS) to geometrically model the distortion of the perceptual space due to the magnet effect. The results demonstrated a strong relationship between category goodness and discrimination. Vowel tokens receiving high goodness ratings in experiment 1 were more difficult to discriminate in experiment 2 and were more tightly clustered in the MDS solutions of experiment 3. These findings support the existence of a perceptual magnet effect, and may help explain some aspects of first language learning in infants and second language learning in adults.

Humans↗
PubMed1993

Isolating the dynamic attributes of musical timbre.

Three experiments examined the dynamic attributes of timbre by evaluating the role of onsets in similarity judgments. In separate experiments, subjects heard complete orchestral instrument tones, the onsets of those tones, and tones with the onsets removed ("remainders"). Ratings for complete tones corresponded to those for onsets, indicating that the salient acoustic attributes for complete tones are present at the onset. Ratings for complete tones also corresponded to those for remainders, indicating that the salient attributes for complete tones are present also in the absence of onsets. Subsequent acoustic analyses demonstrated that this pattern of similarity was due to the centroid frequencies and amplitude envelopes of the tones. The results indicate that the dynamic attributes of timbre are not only present at the onset, but also throughout, and that multiple acoustic attributes may contribute to the same perceptual dimensions.

Acoustic Stimulation↗
PubMed1992

Perceptual interactions between musical pitch and timbre.

These experiments examined perceptual interactions between musical pitch and timbre. Experiment 1, through the use of the Garner classification tasks, found that pitch and timbre of isolated tones interact. Classification times showed interference from uncorrelated variation in the irrelevant attribute and facilitation from correlated variation; the effects were symmetrical. Experiments 2 and 3 examined how musical pitch and timbre function in longer sequences. In recognition memory tasks, a target tone always appeared in a fixed position in the sequences, and listeners were instructed to attend to either its pitch or its timbre. For successive tones, no interactions between timbre and pitch were found. That is, changing the pitches of context tones did not affect timbre recognition, and vice versa. The tendency to perceive pitch in relation to other context pitches was strong and unaffected by whether timbre was constant or varying. In contrast, the relative perception of timbre was weak and was found only when pitch was constant. These results suggest that timbre is perceived more in absolute than in relative terms. Perceptual implications for creating patterns in music with timbre variations are discussed.

Adult↗