Miguelina Guirao

Group and individual gustatory reaction times and Piéron's law

Simple reaction times (SRT) to eight substances belonging to the four classical taste families were evaluated. The same eight subjects participated in all experiments. The functional relationship between SRT and concentration for group and for individual data were examined. Equations presented by different authors to describe RT data are discussed. The Piéron function [(SRT - t0) = betaI-alpha] best fits the gustatory data collected in the present experiments. These results, together with others taken from previous studies, show that the exponent of salt and acid taste functions is lower than 1.0 with a relatively short t0. Sweet and bitter exponents were equal t0 or higher than 1, with a larger t0. Individual performances correlated with taste families for salt and acid. However, the limited samples of some solutions sets some limits to the interpretation of RT to taste substances.

Analysing the contribution of orally perceived attributes to the flavor of wine

The most salient sensory properties of Chardonnay wines are described giving emphasis to the contribution of orally elicited sensations to overall flavor. Nine wines from the main viticulture area of Argentina were evaluated by 13 panelists who identified and rated the intensity of each sensation. Data were analyzed according to the frequency of the terms used and to the intensity assessed. In general, the ranking order of frequency and of intensity levels was similar. A set of 11 out of 18 descriptors turned out to be efficient in describing the wines. The same set allowed a better differentiation between the samples. Most frequently used terms referred to global concepts, basic tastes and other oral attributes The most recurring odorant was apple. Correlation was found between attributes within the same and across modalities. Descriptors were grouped into three spaces each containing a set of odorants centered around related oral attributes.

Identification of argentine Spanish vowels

The acoustical spectrum of the five Spanish vowels |a, e, i, o, u| has been delimited to show the areas covered by F1, F2, and F3 and the relative distribution energy among the formants. Through the analysis of the spectral components of vowels, isolated and in consonantal context, it is possible to estimate the different weight of each formant in vowel identification. At least for isolated vowels,F2 andF3 seem to be effective for the identification of [i] and [e] while theF1 andF2 carry the weight for the identification of [o] and [u]. The cue to differentiate [a] seems to beF2. Spanish vowels are compared with cardinals and North American English vowels. There is no correlation with cardinal vowels while similarities are found with English vowels.

Saturation scales for surface colors

Abstract Magnitude estimations of saturation were obtained for each of 15 pigmented surfaces of different hue, viewed under artificial light in a 4° test field. Saturation was found to be related to colorimetric purity by a power function whose exponent varied with the dominant wavelength. The highest exponents were in the yellow-orange region and the lowest in the blues. Five of the color samples were viewed under both daylight and artificial light with test fields of 4° and 0.7°. The larger visual field and daylight gave somewhat lower exponents for all dominant wavelengths except those in the yellow region. The exponents for saturation of surface colors are systematically higher than those reported for aperture colors.

Direct estimation of lightness of surface colors.

Achromatic and chromatic lightness and darkness of an array of 104 reflecting surfaces were scaled by the method of magnitude estimation. Samples subtended a visual angle of 4° and were viewed under both artificial light and daylight. The dominant wavelengths of the chromatic samples were blue 470, green 553, yellow 574, and red 622 nm. For each hue, the subjective attributes of both lightness and darkness were judged at five levels of colorimetric purity Pc. Both lightness and darkness increased as a power function of the luminous reflectance of the neutral grays and the pigmented surfaces. The lowest exponents, from 0.5 to 0.74, were found among the most and the least saturated samples. Exponents of about 1.0 were obtained for both lightness and darkness functions for the neutral grays, for two Pc levels of red, for one Pc level of green, and one of blue, under both artificial light and daylight. For the yellows, the exponents were close to 1.0 at all purity levels under daylight only. All other samples gave exponents less than one.

Saturation constancy in surface colors

The level of reflectance of pigmented surfaces observed in daylight affects saturation growth in different ways, depending on the wavelength of the samples. Numerical and matching judgments collected in previous experiments were replotted in families of monochromatic (constant hue) saturation power functions for blue, green, yellow, and red. For each hue the set of functions intersected at a point at which the colorimetric purity and saturation were invariant with reflectance. The points of intersection were: blues, 0.081 colorimetric purity (Pc) and 2.7 cromes; greens, 0.257 Pc and 4.6 cromes; yellows, 0.694 Pc and 8.3 cromes; and reds, 0.144 Pc and 3.6 cromes. A straight line fitted to these four intersecting points makes it possible to interpolate other intersecting points for other hues. Two additional experiments were designed to compare a function of saturation with a function of lightness for a set of different hues (heterochromatic functions). Observers judged saturation in one experiment and lightness in the other. Lightness grows linearly with reflectance, and saturation increases as the 0.5 power of Pc, suggesting a different perceptual discrimination for the two dimensions. The relation between changes in quantity and percentage of color perceived was tested in an additional experiment. Observers assigned the following saturation values to the samples with Pc close to the converging points: 13% of color for blues, 20% for reds, 25% for greens, and 40% for yellows.

Saturation of colored samples at various levels of reflectance

The dependence of saturation on the level of reflectance of colored surfaces was measured by numerical estimation and by matching judgments. Four sets of chromatic samples, one for each hue--blue, 460 nm, green, 510 nm, yellow, 580 nm, and red, 620 nm--within a range between 4% and 65% reflectance, were presented to the observers. The largest changes of saturation were observed at the high and low values of reflectance. The effect is more pronounced for the yellows than for the reds and greens, and relatively less apparent for the blues. For each hue, saturation grows faster at intermediate values of reflectance. The four families of saturation functions permitted us to draw a map of equal-purity contours. There are values of colorimetric purity for which saturation remains constant for all levels of reflectance.

Psychophysical Assessments of Sourness in Citric Acid-Ethanol Mixtures

The effect of ethanol in modulating the intensity and duration of the perceived sourness induced by citric acid was studied. Magnitude Estimation-Converging Limits method was applied to rate the sourness of seven solutions (3–70 mM) of citric acid in aqueous solution presented alone and mixed with 8% V/V or 15% V/V ethanol. Dynamic sourness ratings of 5, 15, and 45 mM citric acid alone and mixed with the same two ethanol levels were assessed by the Time Intensity Method (TI). Results were consistent with both methods. Sourness changed with citric acid concentration and ethanol levels. From TI measurements, a similar interactive pattern was obtained for parameters as duration, area under the curve, peak and average intensity.