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PubMed1995

Contextual effects in difference judgments.

Manipulating stimulus spacing, stimulus frequency, or stimulus range usually affects intensity judgments. In six experiments, I investigated the locus of analogues of these contextual effects in a "difference" estimation task. When all stimuli elicited the same taste quality, stimulus distribution affected the scale values only when water was included in the stimulus set (Experiments 1-3). When the subjective ranges of two taste qualities were manipulated, different scale values were obtained for the separate qualities in the two conditions (Experiment 4). Manipulation of the expected response distribution did not affect the scale values or the responses (Experiments 5-6). It is concluded that shifts in stimulus distributions or stimulus ranges result in shifts in subjective scale values. The contextual effects can be interpreted as relative shifts of a number of gustatory continua, with water lying on a separate continuum. Proposed is a model for context-dependent judgments, consisting of four stages: stimulus classification, stimulus placement, continuum placement, and continuum projection.

Adult↗
PubMed1997

Influence of the intensity of NaCl solutions on adaptation degree and recovery time course.

The degree of adaptation and the time course of recovery after adaptation to NaCl solutions of various intensities were examined by magnitude estimation and simple sensory reaction time using a test stimulus of constant intensity. The results show that the degree of adaptation increased with the adapting concentration following a negatively accelerated function. Similarly, all recovery curves were negatively accelerated functions of the recovery time. The relation between the recovery constant (time necessary to attain two-thirds of normal responsivity) and adapting concentration approximates with both criteria more or less a linear function. Thus the recovery constant is a positively accelerated function of the degree of adaptation. The relationship between concentration and degree of adaptation can be approximated by Beidler's equation of taste stimulation, while the time course of recovery can be expressed by an exponential equation that can also be related to Beidler's theory. The two criteria used showed similar deteriorating effects of taste adaptation, indicating that reaction time can also be a useful criterion of the level of sensory responsivity.

Adult↗
PubMed2000

Method of stimulation, mouth movements, concentration, and viscosity: effects on the degree of taste adaptation.

Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrose-soaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.

Adolescent↗
PubMed2000

Influence of sensitivity on response bias in taste and audition.

A detection theoretic analysis was employed to examine sensitivity and response bias in two modalities. In Experiment 1, 6 tasters made same-different judgments about the concentration of either sucrose or quinine in pairs of tonic water samples. The beverages were colored, but color was not predictive of the concentration of the sweet or bitter ingredient. When same-different ratings were collapsed to approximate the outcome of a categorical decision, tasters with poorer sensitivity appear to have adopted more extreme response criteria than did tasters with greater sensitivity, irrespective of taste quality, color, or whether pairs of solutions comprised the same or different colors. In Experiment 2, 3 individuals discriminated pairs of 1000-Hz sinusoids differing in amplitude. Six amplitude differences were tested. Rating-scale versions of two paradigms: The single-interval yes-no task and the two-interval same-different task were used to measure sensitivity and bias. There was a preponderance of "same" responses in the same-different task. Estimates of bias obtained from collapsed ratings in both tasks were unaffected by sensitivity, but a consideration of the range over which sets of criteria were spread suggested a general tendency toward more conservative response biases as sensitivity declined.

Adult↗
PubMed1991

Time course of recovery from gustatory adaptation to NaCl.

Recovery from adaptation to NaCl was tested by comparing some relevant parameters of response to the adapting and test stimuli separated by different recovery intervals. The time course of response was determined using magnitude estimations and using the flow chamber for stimulus delivery. The course of recovery for all parameters used was a negatively accelerated function of the rest time, but the recovery rate of different parameters did not prove to be equal. Recovery was fastest for the initial maximum taste magnitude, followed by the time needed for the taste to disappear. The taste effect summed over time and the time required for the taste magnitude to decrease to 30% of its preadapted maximum were the slowest to recover. Although the recovery processes proceeded at a rapid rate during the initial period, all parameters remained depressed over a rather long period.

Humans↗
PubMed1996

Determinants of cumulative successive contrast in saltiness intensity judgments.

When all stimuli elicit the same taste quality, solutions preceded by a high concentration level are judged to be significantly less intense than solutions preceded by a low concentration level. After repetitious stimulation with a different tasting stimulus, the intensity of the present stimulus is over-estimated. This phenomenon is called "successive contrast." In the present study, the cumulative effects of three identical stimuli on the saltiness ratings for a test stimulus are investigated. The preceding stimuli are manipulated with regard to taste quality, saltiness intensity, total taste intensity, and complexity. Whether the size of the cumulative contrast effect is associated with the degree of dissimilarity between preceding stimuli and test stimulus, or with the saltiness or total taste intensity of the preceding stimuli, is investigated. The size of the contrast effect depends on the type of preceding stimulus, its intensity, and the type of test stimulus. No association was found with judgments of the degree of dissimilarity between the preceding stimuli and the test stimulus. For nonsalty preceding stimuli, the contrast effects are independent of concentration level. When the preceding stimuli taste at least partly salty, the total intensity appears to determine the size of the contrast for an unmixed salty test stimulus.

Adolescent↗
PubMed1999

A confusion matrix for the study of taste perception.

Taste stimulus identification was studied in order to more thoroughly examine human taste perception. Ten replicates of an array of 10 taste stimuli--NaCl, KCl, Na glutamate, quinine. HCl, citric acid, sucrose, aspartame, and NaCl-sucrose, acid-sucrose, and quinine-sucrose mixtures--were presented to normal subjects for identification from a list of corresponding stimulus names. Because perceptually similar substances are confused in identification tasks, the result was a taste confusion matrix. Consistency of identification for the 10 stimuli (T10) and for each stimulus pair (T2) was quantified with measures derived from information theory. Forty-two untrained subjects made an average of 57.4% correct identifications. An average T10 of 2.25 of the maximum 3.32 bits and an average T2 of 0.84 of a maximum 1.0 bit of information were transmitted. In a second experiment, 40 trained subjects performed better than 20 untrained subjects. The results suggested that the identification procedure may best be used to assess taste function following 1-2 training replicates. The patterns of taste confusion indicate that the 10 stimuli resemble one another to varying extents, yet each can be considered perceptually unique.

Adolescent↗
PubMed1994

Sweetness suppression in fructose/citric acid mixtures: a study of contextual effects.

Two experiments investigated whether stimulus context affects ratings for mixtures of dissimilartasting substances (fructose/citric acid) to the same degree that it affects ratings for unmixed substances (fructose). In Experiment 1, replacing mixtures by equisweet unmixed fructose solutions produced virtually no response shifts. The proportion of mixtures in the stimulus set affected only slightly the degree of mixture suppression inferred from the responses. In Experiment 2, both the stimulus type (mixed or unmixed) and the stimulus distribution (positively versus negatively skewed) affected the responses. Several factors that determine the impact of contextual changes are identified: (a) the stage in stimulus processing affected--that of representation on the internal continuum or that of response selection; (b) the size and sources of variation in the affected process; and (c) the degree to which a stimulus is perceptually integrated in the context. In the present study, the sweetness of fructose/citric acid mixtures was largely, but not completely, integrated with the sweetness of unmixed fructose solutions. It is suggested that increased stimulus complexity makes mixture ratings more susceptible to contextual shifts. An analysis relating the size of the contextual shift to the degree of response variability suggests that response-selection processes are more important in determining the responses for unmixed stimuli than they are in determining the responses for mixtures.

Adolescent↗
PubMed2006

Genetic sensitivity to the bitter taste of 6-n propylthiouracil: a new risk determinant for dental caries in children.

The aims of the present study were to contrast the prevalence of dental caries in children with different genetic sensitivity levels to the bitter taste of 6-n-propylthiouracil (PROP) and to determine the taste quality and taste intensity preferences of food products among the taster and nontaster groups. Overall caries experience (dmfs/DMFS) was significantly higher for nontasters than tasters. Caries experience on the available surfaces (dfs/DFS) was found to be significantly higher in nontasters than in medium tasters and in medium tasters than in supertasters (r=-0.41, P < 0.001). Majority of the nontasters were sweet likers and preferred strong tasting food products, while majority of the supertasters were sweet dislikers and preferred weak tastes. There was a significant increase in the overall caries experience in the population, as the genetic ability to detect PROP taste decreased ( P < 0.001). After all associated factors (age, gender, race, number of teeth and OHI-S) were controlled; multiple linear regression analyses revealed that taste was the only variable significantly related to overall caries experience.

Age Factors↗
PubMed1983

Modification of salt taste.

Salt appetite and sodium intake in humans are controlled in part by taste. A distinction can be drawn between salt appetite that occurs when the organism is sodium deficient (in need) and when the organism has sufficient sodium stores (non-need) but continues to ingest salt. Although the latter case is most relevant to human sodium consumption, little is known about its physiologic, developmental, and experiential bases. Recent studies show that changes in dietary sodium consumption are followed by taste changes. Moderate decreases in dietary sodium of 2 months or more are followed by a decrease in the concentration of salt in food judged most pleasant.

Animals↗
PubMed1999

Taste perception in patients with insular cortex lesions.

Research on nonhuman primates suggests that the primary taste cortex in humans is located in the rostrodorsal insula. Qualitative and quantitative assessment of taste perception was performed on 6 patients with unilateral damage to the insula, 3 patients with brain damage outside the insula, and 11 age-matched, normal subjects. Each subject identified the quality and intensity of the gustatory stimuli applied separately to the left and right sides of the anterior tongue. Damage to the right insula produced ipsilateral taste recognition and intensity deficits. Damage to the left insula caused an ipsilateral deficit in taste intensity but a bilateral deficit in taste recognition. The unexpected deficit in the left-hemispheric stroke patients for taste recognition on the right side of the tongue suggests that taste information from both sides of the tongue passes through the left insula.

Adult↗
PubMed2000

Chlorhexidine and taste. Influence of mouthwashes concentration and of rinsing time.

BACKGROUND: This study aims to define the influence of chlorhexidine on taste, considering either its concentration in mouthwashes or time of rinsing. METHODS: Suprathreshold taste acuity of 40 healthy subjects tasting variously concentrated solutions of sucrose, sodium chloride, citric acid and quinine hydrochloride was determined. Subjects were divided into four groups. Three groups rinsed their mouths during one minute, twice a day, for seven days, with a selected mouthwash (respectively 0.12%, 0.20%, and 0.30% chlorhexidine solutions). The fourth group rinsed in the same manner with a 0.30% chlorhexidine mouthwash, and time of rinsing was 15". RESULTS: All the mouthwashes reduced taste acuity for salt and bitter; the perception of sweet and sour was not significantly modified. Chlorhexidine acted on taste in different ways: salt perception reached the lowest value on the second day of treatment and the degree of hypogeusia changed no more till mouthrinses were interrupted. Bitter perception was progressively reduced and reached the lowest value on the seventh day. In both cases taste reduction lasted some days after the interruption of mouthrinses. Quality of all tastes was altered by mouthwashes, but incidence of dysgeusia was not related to chlorhexidine concentration. CONCLUSIONS: Hypogeusia induced by chlorhexidine concerns specifically salt and bitter. Chlorhexidine concentration in mouthwashes till 0.12% and mucosa exposure not exceeding 60" twice a day, seem the best procedure to protect tastes in clinical practice.

Adult↗