Integrality of nasalization and F1. II. Basic sensitivity and phonetic labeling measure distinct sensory and decision-rule interactions.

In vowel perception, nasalization and height (the inverse of the first formant, F1) interact. This paper asks whether the interaction results from a sensory process, decision mechanism, or both. Two experiments used vowels varying in height, degree of nasalization, and three other stimulus parameters: the frequency region of F1, the location of the nasal pole/zero complex relative to F1, and whether a consonant following the vowel was oral or nasal. A fixed-classification experiment, designed to estimate basic sensitivity between stimuli, measured accuracy for discriminating stimuli differing in F1, in nasalization, and on both dimensions. A configuration derived by a multidimensional scaling analysis revealed a perceptual interaction that was stronger for stimuli in which the nasal pole/zero complex was below rather than above the oral pole, and that was present before both nasal and oral consonants. Phonetic identification experiments, designed to measure trading relations between the two dimensions, required listeners to identify height and nasalization in vowels varying in both. Judgments of nasalization depended on F1 as well as on nasalization, whereas judgments of height depended primarily on F1, and on nasalization more when the nasal complex was below than above the oral pole. This pattern was interpreted as a decision-rule interaction that is distinct from the interaction in basic sensitivity. Final consonant nasality had little effect in the classification experiment; in the identification experiment, nasal judgments were more likely when the following consonant was nasal.

The mean-integral representation of rectangles.

To assess perceptual interaction between the height and width of rectangles, we used an accuracy variant of the Garner paradigm. We measured the discriminability of height and width (baseline tasks) and size and shape (correlated tasks). From the d' values in these conditions, we estimated perceptual distances and inferred a mean-integral representation in which height and width corresponded to non-independent dimensions in a perceptual space. This model accounted well for performance in these two-stimulus conditions, and it also explained 70%-80% of the decline in performance in selective and divided attention. In a second experiment, conducted for purposes of comparison with the rectangle discrimination Experiment, we studied the discrimination of horizontal and vertical line segments connected in an L-shape. In size discrimination, observers were equally good with line pairs and rectangles, suggesting holistic perception; but in shape discrimination, they appeared to combine information from the two line-pair components of the rectangle independently. The mean-integral model was again successful in relating performance in the Garner tasks quantitatively.

Integrality in the perception of tongue root position and voice quality in vowels.

In English and a large number of African and Southeast Asian languages, voice quality along a tense-lax dimension covaries with advancement of the tongue root in vowels: a laxer voice quality co-occurs with a more advanced tongue root. As laxing the voice increases energy in the first harmonic relative to higher ones and advancing the tongue root lowers F1, the acoustic consequences of these two articulations may integrate perceptually into a higher-level perceptual property, here called spectral "flatness." Two Garner-paradigm experiments evaluated this interaction across nearly the entire range of tense-lax voice qualities and a narrow range of F1 values. The acoustic consequences of laxness and advanced tongue root integrated into spectral flatness for tenser and laxer but not for intermediate voice qualities. Detection-theoretic models developed in earlier work proved highly successful in representing the perceptual interaction between these dimensions.

d'plus: A program to calculate accuracy and bias measures from detection and discrimination data.

The program d'plus calculates accuracy (sensitivity) and response-bias parameters using Signal Detection Theory. Choice Theory, and 'nonparametric' models. is is appropriate for data from one-interval, two- and three-interval forced-choice, same different, ABX, and oddity experimental paradigms.

Triangles in ROC space: History and theory of "nonparametric" measures of sensitivity and response bias.

Can accuracy and response bias in two-stimulus, two-response recognition or detection experiments be measured nonparametrically? Pollack and Norman (1964) answered this question affirmatively for sensitivity, Hodos (1970) for bias: Both proposed measures based on triangular areas in receiver-operating characteristic space. Their papers, and especially a paper by Grier (1971) that provided computing formulas for the measures, continue to be heavily cited in a wide range of content areas. In our sample of articles, most authors described triangle-based measures as making fewer assumptions than measures associated with detection theory. However, we show that statistics based on products or ratios of right triangle areas, including a recently proposed bias index and a not-yetproposed but apparently plausible sensitivity index, are consistent with a decision process based on logistic distributions. Even the Pollack and Norman measure, which is based on non-right triangles, is approximately logistic for low values of sensitivity. Simple geometric models for sensitivity and bias are not nonparametric, even if their implications are not acknowledged in the defining publications.

Integrality of nasalization and F1 in vowels in isolation and before oral and nasal consonants: a detection-theoretic application of the Garner paradigm.

In vowel height contrasts, tongue height and soft palate height covary. A series of vowel classification experiments examined the perceptual interactions between F1 and nasalization, the principal acoustic correlates of these articulations. Listeners classified imperfectly discriminable stimuli in the set of tasks that compose the Garner paradigm. Detection-theoretic models applied to the data led to the conclusion that vowels, whether in isolation, before oral consonants, or before nasal consonants, display integrality of F1 and nasalization. The contrary conclusion reached by Krakow et al. [J. Acoust. Soc. Am. 83, 1146-1158 (1988)] on the basis of data from a trading relations experiment reflect a limitation of that design for studying perceptual interaction. A second experiment used an array "rotated" in the stimulus space to determine whether F1 and nasalization are privileged, perceptually primary dimensions. A new method for predicting classification performance for the rotated array without the assumption of primacy showed that they are not.

Sound localization precision under conditions of the precedence effect: effects of azimuth and standard stimuli.

Minimum audible angles (MAAs) were estimated for single noise bursts, and for burst pairs that satisfied the conditions of the precedence effect (that is, produced fused images). In one burst-pair condition, the bursts to be discriminated differed in lead location; in the other, they differed in lag location. Sounds were presented over loudspeakers. MAAs were lowest for single bursts, slightly higher for lead discrimination, and much higher for lag discrimination. Presence of a standard reference burst had no reliable effect on performance. The data are interpreted using a model of Shinn-Cunningham et al. [J. Acoust. Soc. Am. 93, 2923-2932 (1993)] in which discrimination of precedence-effect burst pairs is based on the lateral position of the auditory image, which is a weighted average of the positions of the leading and lagging bursts.

Auditory phase and frequency discrimination: a comparison of nine procedures.

Two auditory discrimination tasks were thoroughly investigated: discrimination of frequency differences from a sinusoidal signal of 200 Hz and discrimination of differences in relative phase of mixed sinusoids of 200 Hz and 400 Hz. For each task psychometric functions were constructed for three observers, using nine different psychophysical measurement procedures. These procedures included yes-no, two-interval forced-choice, and various fixed- and variable-standard designs that investigators have used in recent years. The data showed wide ranges of apparent sensitivity. For frequency discrimination, models derived from signal detection theory for each psychophysical procedure seem to account for the performance differences. For phase discrimination the models do not account for the data. We conclude that for some discriminative continua the assumptions of signal detection theory are appropriate, and underlying sensitivity may be derived from raw data by appropriate transformations. For other continua the models of signal detection theory are probably inappropriate; we speculate that phase might be discriminable only on the basis of comparison or change and suggest some tests of our hypothesis.