RESUMEN
Discrimination tests are used in food companies to quantify small differences between products. Within the diversity of methods available, some are quicker to conduct, whereas others are more sensitive or statistically powerful. One class of methods includes the reminder tasks in which the reference product is given before tasting the actual test stimuli. During the task, such a 'reminder' can be compared directly to each test stimulus, or alternatively, only serve to prime the memory of the judge without being taken into account in decision-making. Previous research with trained judges provided evidence for the latter process while research with untrained consumers has provided some evidence for the former process. Two studies were conducted with untrained consumers using the A Not-AR and 2-AFCR reminder tasks. Objectives were to determine the decision strategies used in, and the relative sensitivity of the tasks. In addition, the use of an "authenticity test" was explored to see if this has a positive effect on test performance. In the first study, mayonnaise and ice tea with small stimulus differences (d'<1) were used in A Not-AR and 2-AFCR. Results were compared to those from A Not-A and 2-AFC tasks, with and without an authenticity test. It was difficult to draw clear conclusions on the decision strategy used, though the use of an authenticity test increased the sensitivity for these small differences, as it improved the performance of 6 out of 8 tests. In the second study, ice teas with larger stimulus differences (at two levels) were tested using the A Not-AR and 2-AFCR tasks, in comparison to the same-different task. The results showed that consumers use the less optimal strategies and that the authenticity test decreases performance, which is contradictory to the results of the first study. It seems that for very small stimulus differences the authenticity test can improve performance, but with larger differences the authenticity test decreases performance; it seems to confuse the judges.
Asunto(s)
Comportamiento del Consumidor , Toma de Decisiones/fisiología , Alimentos/normas , Adolescente , Adulto , Femenino , Industria de Alimentos , Humanos , Masculino , Proyectos de Investigación , Gusto , Té , Adulto JovenRESUMEN
The decision strategy adopted by an observer in a psychophysical procedure may be established by comparing estimates of sensitivity obtained by using detection-theoretic models based on each of the available decision strategies. Estimates of sensitivity obtained from 10 observers on auditory-level discrimination tasks using the yes/no, two-alternative forced choice (2AFC), and 2AFC with reminder (2AFCR; sometimes called duo-trio) procedures were compared in order to determine the decision strategy used by the judges in the 2AFCR procedure. 2AFCR permits at least three decision strategies: differencing, likelihood ratio, and comparison of distances. The latter strategy has frequently been assumed in the analysis of duo-trio data in the sensory evaluation literature. The present study demonstrates that the comparison-of-distances strategy was not used by 9 of the 10 observers in this auditory experiment. The nature of the instructions given to the observers had no measurable impact on the decision strategy that they adopted.
Asunto(s)
Conducta de Elección , Toma de Decisiones , Percepción Sonora , Memoria a Corto Plazo , Discriminación de la Altura Tonal , Detección de Señal Psicológica , Estimulación Acústica , Femenino , Humanos , Funciones de Verosimilitud , Masculino , Aprendizaje por Probabilidad , Psicoacústica , Curva ROC , Aprendizaje InversoRESUMEN
In recent EEG investigations [Johnson, 2003] [Hautus, 2005], we described a novel late negative ERP component associated with binaural processing of auditory pitch based solely on interaural timing differences ("dichotic pitch"), an acoustic phenomenon that is closely analogous to visual perception of stereoscopic depth based on retinal disparities. The present study extends this research with neuromagnetic recordings of auditory evoked fields (AEFs) elicited by dichotically-embedded pitches. Eight healthy adult subjects listened to control stimuli consisting of 500 ms segments of broadband acoustic noise presented identically to both ears via earphones, and dichotic pitch stimuli created by introducing a dichotic delay to a narrow frequency region of the same noise segments and resulting in a perception of a pitch lateralized to the left or right of auditory space. Auditory-evoked fields (AEFs) were recorded using a 151 channel whole-head MEG system. Comparison of control and dichotic-pitch AEFs showed reliable amplitude differences during a time window of 150-350 ms. AEFs over the left hemisphere showed larger effects for contralateral than ipsilateral pitches, while the right hemisphere showed no differences for differently lateralized sources. The results indicate a relatively late stage of neural processing of binaurally-derived cues for the perceptual segregation of concurrent sound sources and support a right-hemisphere dominance for the processing of sound-source localization.
Asunto(s)
Estimulación Acústica/métodos , Corteza Auditiva/fisiología , Potenciales Evocados Auditivos/fisiología , Magnetoencefalografía/métodos , Percepción de la Altura Tonal/fisiología , Adulto , Mapeo Encefálico/métodos , Femenino , Lateralidad Funcional/fisiología , Humanos , Masculino , Localización de Sonidos/fisiologíaRESUMEN
The same-different experiment is popular for assessing perceptual performance, including the performance of people with neuropsychological deficits. Although the measurement of accuracy with this experiment is now well understood, the measurement of response bias remains problematic. Reformulating the decision space for the experiment can yield new bias indices that are analogous to, but numerically different from, those of the more familiar yes-no experiment. Isobias curves that show how hit rate covaries with false alarm rate for constant bias but varying accuracy are presented for eight indices, and best-fitting parameters of the isobias functions are determined for a set of experimental data. The theoretical status of the bias indices and their relation to other formulations are reviewed.
Asunto(s)
Percepción de Color , Toma de Decisiones , Aprendizaje Discriminativo , Reconocimiento Visual de Modelos , Adulto , Cara , Femenino , Humanos , Masculino , Distorsión de la Percepción , PsicofísicaRESUMEN
If observers in a same-different experiment base their decisions on the absolute difference between observations on a trial, the area under the receiver operating characteristic equals the maximum proportion of correct decisions that an unbiased independent-observations observer could attain. Even though the differencing strategy is suboptimal, the area measure yields an index of optimal performance.
Asunto(s)
Juicio/fisiología , Psicofísica/estadística & datos numéricos , Curva ROC , Detección de Señal Psicológica/fisiología , Análisis y Desempeño de Tareas , Interpretación Estadística de Datos , HumanosRESUMEN
The dispersions of estimates of sensitivity obtained from the yes-no, two-alternative forced-choice (2AFC), matching-to-sample, and same-different tasks were examined to determine which task would be more appropriate to use in a given experimental context. Consideration was given to the effects of corrections for extreme sampled proportions. These corrections result in biased estimators, and hence the mean-square deviation of the sampled values about the population mean [MSD(d')], rather than that about the mean of the estimates [VAR(d')], indicates more completely the extent of the error in the estimator. For barely discriminable events (d' approximately equal to 0.5), the yes-no and 2AFC tasks had the lowest values of MSD(d'). However, for very discriminable events(d > 3), the same-different and matching-to-sample tasks had lower values of MSD(d').
Asunto(s)
Modelos Teóricos , Detección de Señal Psicológica/fisiología , Humanos , Psicofísica , Factores de TiempoRESUMEN
Receiver-operating characteristics for the discriminability in the length of the lines of the Müller-Lyer figure were obtained by the rating method of detection theory. Six observers judged the shaft length of the lines of the figure with reference to the same standard line. Maximum-likelihood estimates of the index of discriminability, d', were linear function of the difference in the length of the lines, but the functions did not pass through the origin because of a constant error of judgment. Because discriminability was determined by ROC analysis, the constant error could not be attributed solely to changes in criterion placement; instead, it showed that the Müller-Lyer figure induced a change in the discriminability of the lines.
Asunto(s)
Percepción Visual/fisiología , Femenino , Humanos , Masculino , Ilusiones ÓpticasRESUMEN
An optimal decision strategy for deciding whether two things are the same or different is to adopt a likelihood-ratio criterion. The parametric equations for the receiver operating characteristic (ROC) based on the likelihood-ratio strategy when observations are independent are complicated; they require the numerical evaluation of a double integral. An approximation to the parametric equations for the likelihood-ratio strategy was developed. This approximation takes the form of a pair of equations that describe ROCs virtually indistinguishable from those of the full model.
Asunto(s)
Toma de Decisiones , Aprendizaje Discriminativo , Funciones de Verosimilitud , Modelos Estadísticos , Humanos , Psicofísica , Curva ROCRESUMEN
We examined the ability of a bottlenose dolphin (Tursiops truncatus) to recognize aspect-dependent objects using echolocation. An aspect-dependent object such as a cube produces acoustically different echoes at different angles relative to the echolocation signal. The dolphin recognized the objects even though the objects were free to rotate and sway. A linear discriminant analysis and nearest centroid classifier could classify the objects using average amplitude, center frequency, and bandwidth of object echoes. The results show that dolphins can use varying acoustic properties to recognize constant objects and suggest that aspect-independent representations may be formed by combining information gleaned from multiple echoes.
Asunto(s)
Delfines , Ecolocación , Acústica , Animales , Conducta Animal , Aprendizaje Discriminativo , Percepción de Forma , MasculinoRESUMEN
In three experiments on the psychophysical measurement of pain, electrocutaneous currents were applied to the volar surface of the forearm. In the first experiment, a conventional category scaling method was compared with the rating method of signal detection. The results of both methods were analyzed in detection-theory terms to derive receiver operating characteristic curves and measures of the discriminability of adjacent currents. The rating method yielded larger discriminability values than the category scale did, and that method was therefore used in the subsequent experiments to examine the effect of a topical anesthetic on discriminability. When the stimuli were applied through surface electrodes, no effect of the topical anesthetic on discriminability was found, but when the stimuli were applied to a more localized area by intradermal needle electrodes, a dose-dependent effect of the anesthetic on discriminability occurred. For this experiment, the slope of the cumulative sensitivity function increased with increasing elapsed time since the removal of the anesthetic. This result is congruent with the theory that discriminability can serve as a measure of sensitivity to painful stimuli.
Asunto(s)
Anestesia , Aprendizaje Discriminativo , Estimulación Eléctrica , Dimensión del Dolor , Dolor , Piel , Electrodos , Humanos , Umbral del DolorRESUMEN
The ability of human observers to discriminate differences in the amplitude of sinusoids and narrow-band noises was measured by the rating method of detection theory. Although each sinusoid (always 1000 Hz) was presented at a fixed amplitude, its amplitude on any trial was drawn from one of two Rayleigh probability distributions that differed in mean amplitude: a signal distribution and a noise distribution. Similarly, the amplitudes of the narrow-band noises were distributed as the Rayleigh distribution by virtue of the reciprocal relation between their bandwidth (100 Hz centered on 1000 Hz) and duration (10 msec). The obtained psychometric functions showing the area under the ROC as a function of signal-to-noise ratio were similar for both kinds of signals and were displaced, on average, about 4 dB from an ideal observer's function. The slopes of the obtained functions were similar to those of an ideal observer using 1 degree of freedom--half the number available in Rayleigh noise.