Comparison of taste qualities elicited by tactile,electrical, and chemical stimulation of single human taste papillae

Taste quality responses elicited by chemical, electrical, and tactile stimulation of 40 single fungiform papillae in four subjects were examined. A comparison of responses revealed differences in taste quality mediation for the three different classes of stimuli. Chemical stimulation elicited multiple taste qualities from a greater proportion of papillae than did either electrical or tactile stimulation. In addition, the chemical data revealed the presence of consistent bitter-sour and sour-salty confusions. Both tactile and electrical stimulation elicited relatively few bitter and sweet responses, as compared with either sour or salty responses. However, correct quality identification in these papillae for bitter and sweet compounds was no different from that for sour or salty compounds. In addition, electrical stimulation elicited a greater proportion of salty responses than did tactile stimulation. Comparison of the taste quality elicited by either tactile or electrical stimulation of a papilla with the taste quality exhibiting the greatest relative chemical sensitivity in the papilla also revealed independence of responding, and it was observed that both electrical and tactile stimulation elicited consistent taste quality responses from papillae in which these taste qualities could not be elicited by any concentration of any chemical test compound. The observed differences in quality judgments are discussed as possibly being the result of cross-modal gustatory associations resulting from nongustatory components of inadequate stimulation.     

The roles of practice and correction in the categorization of sour and bitter taste qualities

Ten Ss were selected from a group of 40 screened to determine misnaming of stimuli usually called sour (hydrochloric and citric acid) and bitter (quinine sulfate). The 10 Ss were then given 16 trials in which they were asked to match the stimuli to standards, with or without verbal feedback for each stimulus. This was followed by 16 trials without feedback for all Ss and, several days later, by a 16-trial posttest. Final improved performance of the Ss was not affected by having received the feedback. It was concluded that experience with the stimuli leads to a reduction in the degree of misnaming, implying a nonphysiological basis for sour-bitter confusions.     

Quality-specific effects of aging on the human taste system

Elderly persons are known to have elevated taste thresholds, with those for bitter more affected by age, for example, than those for sweet. Do analogous quality-specific effects occur at suprathreshold levels? Young (mean age = 20.3 years, SD = 2.99) and elderly (mean age = 72.5 years, SD = 4.58) subjects made magnitude estimates of sweetness, bitterness, sourness, and saltiness for the unmixed components sucrose, caffeine, citric acid, and NaCl at three concentration levels for each. They also made magnitude estimates of the separate taste qualities in two-component mixtures of sucrose with each of the other three qualities, at various levels of the two components in each mixture. Magnitude estimates of taste intensity were interweaved with magnitude estimates of the heaviness of six weights, which subjects were to judge on the same subjective intensity scale: This is the calibration feature of the method of magnitude matching, and permits the comparison of elderly and young subjects on the absolute intensity of tastes. When unmixed components were judged, elderly subjects found the characteristic tastes of caffeine and citric acid less intense than, but those of sucrose and NaCl as intense as, younger subjects did. In judging mixtures, the elderly found bitterness, but not the other three qualities, less intense than did the young subjects.     

Spatial interactions of taste stimuli on the human tongue

Two nearby loci on the human tongue were stimulated with solutions representing the four basic taste qualities. The recognition threshold for each test stimulus was measured when a strong concentration of one of the four qualities or water was placed nearby. Decreased sensitivity for the test stimulus resulted when both stimuli were the same quality, with the exception of an enhancement of bitter sensitivity by QHCl. The only effect across qualities was a suppression of citric acid by NaC1. In contrast, classical studies reported across-quality enhancement. Stimulation of two loci on the same half of the tongue and the use of modern psychophysical techniques may explain the differences between these and earlier results.     

Psychophysical exponents for single papillae: A comparison with whole-mouth exponents

Taste intensity judgments in response to chemical stimulation of single human fungiform papillae were obtained by the method of magnitude estimation. Intensity scales constructed from these data were compared to those obtained from the same subjects in response to stimulation of the whole mouth. Single papilla functions conformed well to the power law governing the growth of sensation magnitude, although a minority of single papilla functions exhibited peaking of response magnitude at intermediate concentrations, followed by a decline in response magnitude at higher concentrations. Single papilla exponents were found to be lower than whole mouth exponents and were positively correlated with detection and/or recognition thresholds of the papillae for most compounds. Exponents of summated single papilla functions were greater than median single papilla exponents, but their relative magnitude vs. whole mouth exponents varied by test compound. The data were discussed in relationship to previous findings concerning flow rate effects, threshold-exponent relationships across the tongue surface, and level-dependent spatial summation.     

Ingestive responses of human newborns to salty, sour, and bitter stimuli.

Human newborns (1-4 days old) were offered two fluids differing in taste for 3 min each. The volumes ingested were measured. Infants offered water and bitter or sour solutions did not ingest them differentially, which corroborated earlier observations with weaker solutions. A sucrose solution was used to raise baseline ingestion above that of water. Infants offered the sucrose solution with and without urea, citric acid, or sodium chloride consumed less of it when citric acid was added. They were indiffferent to the addition of urea or sodium chloride. The failure to observe intakes lower than that of water suggests that newborns maximally inhibit their ingestion of water. The effects of sex, age, birth weight, and individual consistency on intake were assessed.     

Visual influence on taste sensitivity

A claimed dependence of taste sensitivity on body state, accepted for 40 years, is investigated in two experiments. Neither the growth of sensation above threshold, as measured in a magnitude estimation experiment, nor taste sensitivity near threshold, as measured by a signal detection analysis, show the claimed increment when individuals are dark-adapted. On the contrary, in both cases, performance is superior in the light, when subjects taste with their eyes open, possibly due to an arousing effect of concurrent visual stimulation.     

Preconceptions of taste based on color

The authors examined preconceptions of taste based on color with a questionnaire administered to 45 college students. The questionnaire related 8 tastes with 10 colors. The results suggested that only a limited number of colors are positively associated with preconceptions of taste. However, certain colors (e.g., red and green) showed consistent patterns of association with taste. Implications for future research examining an indirect relationship between color and taste are discussed.     

The effect of background music on the taste of wine

Research concerning cross-modal influences on perception has neglected auditory influences on perceptions of non-auditory objects, although a small number of studies indicate that auditory stimuli can influence perceptions of the freshness of foodstuffs. Consistent with this, the results reported here indicate that independent groups' ratings of the taste of the wine reflected the emotional connotations of the background music played while they drank it. These results indicate that the symbolic function of auditory stimuli (in this case music) may influence perception in other modalities (in this case gustation); and are discussed in terms of possible future research that might investigate those aspects of music that induce such effects in a particular manner, and how such effects might be influenced by participants' pre-existing knowledge and expertise with regard to the target object in question.     

Receiving advice on matters of taste: Similarity, majority influence, and taste discrimination

People routinely consider the opinions of others prior to making decisions on matters of taste (e.g., a restaurant or movie). Our theoretical framework highlights the role of two sources, social (majority) influence and similarityamong advisors, in such decisions. We suggest that individuals’ use of these sources depends on their taste discrimination. While highly discriminating judges seek the opinion of a similar advisor rather than the majority opinion, less discriminating judges do so less. In four studies participants made musical choices based on recommendations. The studies document the great appeal of behavioral similarity and the role of demographic similarity. They also provide evidence for the discrimination hypothesis. A formal simulation is developed to account for the relationship between taste discrimination and the predictive accuracy of the majority and of similar advisors. The results shed light on theories of advice utilization and social influence, and are connected with applications involving personalized recommendation systems.     

Psychophysics of taste lateralization on anterior tongue

There have been very few investigations of the spatial properties of taste stimuli localized to specific areas of the oral cavity. This is surprising, since the spatial localization of taste sensations may contribute to the overall taste percept, much as do quality, intensity, and the temporal characteristics of tastes. The difficulty in eliminating the confounding factor of a tactile sensation may partially account for the paucity of such studies, since a gustatory stimulus cannot be presented as a liquid without a tactile component. As a step toward understanding the localizability of gustatory sensations, we designed a yoked stimulator and an experimental procedure to control for tactile cues. Lateral discrimination was evaluated at the tip of the tongue with four taste stimuli (sodium saccharin, sodium chloride, citric acid, and quinine hydrochloride) by presenting a taste and a blank solution simultaneously at two locations on the tongue. We found that subjects could lateralize all four taste stimuli in the absence of any discriminative tactile cues. Subjects' ability to lateralize varied as a psychometric function of the stimulus concentration. Detection thresholds, measured in a forced-choice two-interval staircase procedure with the same yoked stimulator that was used in the lateralization task, were always lower than lateralization thresholds, and both lateralization and detection thresholds were correlated within subjects. Subjects were unable to lateralize taste cues on a nongustatory surface under the upper lip at the highest tested concentrations, at which performance was 100% on a gustatory surface (dorsal anterior tongue). These results show that (1) taste compounds can be lateralized in the absence of any discriminative mechanical cue (but only on the gustatory epithelium) and (2) although the localization of a compound does not logically require conscious detection of the taste (cf. blind sight), subjects always detected a taste when they were able to lateralize.     

Effect of response task on taste adaptation

Two experiments studied whether subjects reported complete adaptation of a taste sensation. Three tasks were chosen based on their use in other laboratories: hand lowering to connote stimulus absence, magnitude estimation, and cross-adaptation of a brief stimulus following a prolonged stimulus. In the first experiment, different groups of 9 subjects received the three different tasks; in the second experiment, all 20 subjects received all three tasks. In both experiments, subjects failed to demonstrate complete taste adaptation in at least 50% of adaptation trials. Response task did affect the likelihood of observing complete taste adaptation.     

Adaptation effects on evoked electrical taste

In spite of a clear increment in absolute thresholds as an effect of self-adaptation, the electrically provoked taste sensation does not show a reduction in subjective intensity during the protracted stimulation time. Chemical cross-adaptation effects on the threshold and suprathreshold levels of electrical taste are observed only when the adapting solutions are electrolytes regardless of their taste qualities. It seems that the stability of perceived intensity during current flow is principally due to some irritation of the sensitive tissue of the tongue, whereas cross-adaptation effects may be attributed to the potential changes across the excitable membranes caused by electrical properties of adapting electrolytic solutions.     

The effect of adaptation on taste jnds

The jnd for 0.1 M NaCl was measured under two different adapting conditions. Following adaptation to HOH the jnd was 0.009 M and after 0.1 M adaptation it was .018 M. The implications of this change in sensitivity with differing adaptation for Beidler’s theory are discussed.