Detection of heteroquality taste mixtures

Detection thresholds were measured for sweet (sucrose), salty (sodium chloride), sour (citric acid), and bitter (quinine hydrochloride) and for the 11 possible mixtures of these four substances. These 11 mixtures (6 binary, 4 ternary, and 1 quaternary) all turned out to be stimulus additive, in the sense that a person could reliably detect mixtures whose individual components are weaker than their unmixed thresholds. Tastants too weak to be perceived alone can thus make impact when in mixtures. The threshold concentration for a given compound was reduced in approximate proportion to the number of compounds added to it. This liberal heteroquality additivity contests the widespread belief that heteroquality mixtures (different chemicals evoking different qualities) are nonadditive and homoquality mixtures (different chemicals evoking the same quality) are additive. Heteroquality additivity emerges on appropriate definition of the subject’s task by forced choice (unavailable to earlier investigators), in order to skirt methodological pitfalls. Operating together, homoand heteroquality additivity may concomitantly enable a person to sense natural mixtures of hosts of weak constituents, such as drinking water. In this regard, gustatory mixtures may function much as do mixtures of frequencies in audition and mixtures of gaseous compounds in olfaction.     

Parallel—and distance—alleys with moving points in the horizontal plane

Stimulus points were presented on the horizontal plane of eye level under both dark and illuminated homogeneous spaces. When two apparent movements towards the subject were generated and positions of points were so adjusted that the two movements appeared straight and parallel (P alley) or with a constant lateral distance (D alley), the D alley lay outside the P alley, as traditionally shown with stationary sets of points. The two alleys were constructed with various patterns and velocities of movement, and the Lüneburg formulas were used as experimental equations to describe the results. The equations have two parameters: K (curvature) and o (sensitivity in depth perception). Values of K and o obtained with stationary points in previous experiments are shown too. Predominantly, K < 0 (hyperbolic), and the same is true in the present study. No first-order effect of patterns and velocities of the movement upon K and o was found.     

Directional information and apparent movement—The apparent movement to apparent simultaneity threshold

This paper reports a study of changes in apparent movement to apparent simultaneity thresholds as a function of the directional information of the second point of light. An earlier paper (Jeeves and Bruner, 1956) reported changes in thresholds from apparent movement to apparent successiveness when the same experimental variable was manipulated. In interpreting the results the authors proposed an hypothesis in terms of “attentional disarticulation.” Brown (1956) commenting on this earlier paper put forward an alternative explanation of the results in conventional informational terms and he predicted the changes in the apparent movement to apparent simultaneity thresholds which should occur if studied under the same experimental conditions. He further showed that his predictions would differ from predictions made on the basis of our own explanation. The results of the experiment reported here uphold the predictions of our own earlier theory and fail to fit those made by Brown. However, in attempting to understand the results from the two experiments considered together, it is suggested that a factor must be included which was omitted from our own earlier explanation but emphasized by Brown. This factor as stated by Brown (1956) is “that the threshold for a discrimination tends to increase with the information content of any discrimination which has to be made concurrently.”     

Specularity,brightness, achromatic color&#x2014;and orthogonality

For objects under the same illumination, the more specular object appeared brighter. This occurred irrespective of an object’s apparent achromatic color, the distance at which it was viewed, the level of illumination, the method used for collecting observations, and other conditions. Also, when identical specular objects were differently illuminated, the one under the higher illumination, with the higher maximal luminances, appeared brighter. In the five experiments, which involved 340 subjects subdivided into 17 groups, large fields of view and real spaces were used. The results supported the conclusion that apparent brightness and achromatic color are orthogonal phenomena, and that in four of these experiments increased apparent brightness was correlated to, if not determined by, maximal specular luminances without regard to achromatic colors and diffuse luminances. This conclusion was necessarily modified by a fifth experiment, which showed that if placed under sufficiently high levels of illumination, less specular surfaces appeared brighter than more specular surfaces. This was taken to mean that a total account of the apparent brightness of surfaces would depend on an undiscovered algorithm involving maximal specular and diffuseluminances and their areal extents. With regard to the validity of the studies, the subjects were shown to have phenomenally discriminated brightness from glossiness and glare. Finally, phenomenal gloss and glare were found to be correlated to a surface’s level of specularity.     

Attention,extraversion, and stimulus&#x2014;personality congruence

In this study Ss classified as extraverts, ambiverts or introverts on the Maudsley Personality Inventory looked at photographs rated as extravert, ambivert, or introvert for as long as they wished. It was hypothesized that there would be a tendency for Ss to look relatively longer at pictures congruent with their personality characteristic. Support for this hypothesis was found in a significant picture by personality interaction. Extraverts clearly looked longer at extravert pictures and introverts showed a very s light preference for introvert pictures. Ambivert pictures were looked at the longest by all groups. This high looking time for ambivert pictures and the small difference between the looking time at extravert and introvert pictures by introvert Ss is explained in terms of greater complexity of the ambivert and extravert pictures used in this experiment.     

Effects of electrocutaneous ready&#x2014;signal variation on visual reaction time

Two ready-signal variables (direction of change in electrocutaneous stimulation and method of presentation: “trace” or “delayed”) were combined in a 2 by 2 by Ss design. Neither variable produced a significant main effect but yielded a highly significant interaction. Results were interpreted in terms of arousal. intersensory. and conditioning explanations of ready-signal effects.     

On the scaling of visual space from motion&#x2014;in response to Pizlo and Salacfa-Golyska

Pizlo and Salack-Golyska (1994) have raised an important question about the validity of the interpretation of experiments reported by Lappin and Love (1992)&#x2014;based on the fact that alternative cues in the image plane might have supported the shape discriminations in those experiments. The meaning of the hypothesis that visual space may be scaled by congruence under motion is clarified, pertinent evidence is reviewed, and new experimental evidence is reported We conclude that visual space can be metrically scaled by congruence of moving shapes.     

Magnitude production and magnitude estimation of taste intensity

Magnitude productions of sodium chloride (salty), quinine hydrochloride (bitter), and sucrose (sweet) yielded steeper psychophysical functions than those obtained with magnitude estimation. Hydrochloric acid (sour) produced the opposite effect. The results are discussed with respect to previous findings in taste intensity scaling and to general psychophysical considerations.     

The duration and perceived intensity of sucrose taste

Thirty-two subjects judged the perceived intensity of each of four concentrations of sucrose over 2 min. Stimuli were either sipped and expectorated or flowed over the subject’s extended tongue. Ratio judgments on a line scale and category ratings were made. Sixteen of the subjects had had extensive training in judging the sensory attributes of food products, and another group of 16 subjects were untrained. The perceived intensity of sucrose rose to a peak within 5 or 10 sec, and then declined over 2 min. In both the sip and the flow conditions, the taste disappeared completely for 26 of 32 subjects. Stronger concentrations were perceived as having greater peak intensities and longer lasting taste. The differences between concentrations were enhanced when sipped rather than flowed over the tongue. Judgments of intensity and duration were largely unaffected by the training level of subjects and the use of different rating scales.     

The limited capacity of humans to identify the components of taste mixtures and taste-odour mixtures

The capacity of humans to identify the components of taste mixtures and odour-taste mixtures was investigated in two experiments. Subjects were trained to identify the components presented alone and to use a 'yes/no' procedure to identify them in mixtures. All stimuli were presented with a retronasal (by mouth) technique. A maximum of three tastants were identified in both types of mixtures, only one tastant was identified in five-component taste mixtures, and no component was identified in four-component odour-taste mixtures. Importantly, in no instance was the olfactory stimulus identified in any mixture with tastes, including binary mixtures. Loss of identity of the odorant in binary and ternary mixtures may have been due to suppression as a consequence of temporal processing, or to the absence of an association between the odorant and tastants that had established an identifiable percept. In contrast, poor identification of the components of the quaternary odour-taste mixture and quinternary taste mixture is attributed to the limited capacity of working memory. Overall, the poorer ability to identify components in odour-taste mixtures than in taste mixtures indicates that interactions occurred between the two senses, challenging the proposal that odours and tastes are processed independently when present in complex chemosensory stimuli.     

The equiratio taste mixture model successfully predicts the sensory response to the sweetness intensity of complex mixtures of sugars and sugar alcohols

The equiratio taste mixture model was originally developed for the prediction of psychophysical power functions of equiratio mixtures of substances that have a similar taste and that also exhibit mutual cross adaptation. Earlier studies have shown that the model is valid for mixtures of sugars and/or sugar alcohols. Two experiments are reported in which it is questioned whether the psychophysical functions of mixtures of higher physical complexity can be predicted by the model. In the first experiment the psychophysical power functions of binary and quaternary equiratio mixture types were determined experimentally and compared to those predicted by the generalized model. In the second, similar, experiment quaternary and eight-component mixture types were examined. The method of magnitude estimation, in combination with the sip and spit procedure, was used. The functions predicted by the model were almost identical to the functions established on the basis of the experimental data. These results reconfirm that the gustatory modality operates like an 'averaging' system when processing this kind of mixture. It is argued that for other kind of mixtures the model will predict incorrectly. The status of the equiratio mixture model is discussed.     

A note on the relation between area and intensity in taste

Taste thresholds as a function of area previously published [Hara, 1955) are reanalyzed and found to be described better by the hyperbolic relation C×Aⁿ=k than an exponential equation. The exponent. n, and the constant, k, were found to differ among taste compounds.     

Effects of taste quality and intensity on oral perception of viscosity

Oral assessments of viscosity were obtained with the method of magnitude estimation. Subjects judged the viscosity of a series of aqueous solutions thickened to one of six viscosity levels (1–2025 centistokes) with a food-grade gum, sodium carboxymethylcellulose. The solutions contained one of several concentrations of caffeine, citric acid, sodium chloride, or sucrose. The presence of taste substances significantly altered the perception of solution viscosity for only the thickest solutions. Increasing concentrations of citric acid and sodium chloride produced progressive decreases in perceived viscosity, and increasing sucrose concentrations produced small increases in perceived viscosity. Caffeine did not affect judgments of solution viscosity. The most likely explanation for these findings is that subjects detected differences in the Newtonian behavior of the thickened solutions, differences that were produced by the addition of taste substances.     

Fear decrement to anxiety hierarchy items—Effects of stimulus intensity

The effects of hierarchy item intensity and duration of presentation on intra-item fear decrement were assessed with regard to systematic desensitization. Forty-eight color slides of snakes were scaled and ranked for anxiety value with the psychophysical technique of magnitude estimation by 30 female snake phobics using two response methods: verbal report and a non-verbal report instrument, the hand dynamometer. Seven test slides, spanning the scale range, were shown for 257 sec to 42 additional subjects who rated their fear level on 10 separate occasions using the hand dynamometer and verbal report. For all slides significant fear decrement occurred as a function of duration and the fear decrement across time was greater for slides of higher intensity. Negative exponential functions with similar slopes were found to fit the data for each of the slides, indicating that for each slide the same percentage of the total amount of fear decrement was lost per unit of time. The implications of these results and techniques are discussed for desensitization theory, research and therapeutic procedure.     

Detection and recognition of increments and decrements in auditory intensity

Os’ performance in the detection of increments and decrements in the intensity of a pure tone was compared with their performance in an increment-decrement recognition experiment. Recognition performance improved, relative to detection performance, as signal duration increased. This is surprising from the point of view of all stimulus models within signal detection theory. These data and others are described in terms of a change detection mechanism.     

Detection of increments in noise intensity by monkeys

Monkeys were trained to detect 100-msec increments in the intensity of continuous white noise. A response on one of two bars was reinforced with some probability if it conformed to the presence or absence of the increment on that trial. Stimulus parameters of background intensity, increment size, and probability of increment presentation were varied, and response probabilities and latencies were recorded. The task was analogous to the "yes-no" task used in human psychophysics. Data analysis within the context of signal-detection theory revealed response biasing toward one bar or the other to be related to the probability of increment presentation, whereas sensitivity depended on the combination of increment size and background noise intensity. Weber's law was found to hold for a large range of background intensities in that the sensitivity to relative intensity increments varied little. Performance was compared to that of an ideal observer that uses samples of the envelope of the noise waveform on which to base its responses.     

Context effects in judging taste intensity: A comparison of variable line and category rating methods

The effect of stimulus range and stimulus spacing was examinedwhen subjects registered the perceived intensity of sweet liquids using either a matching procedure (Experiment 1) or category rating (Experiment 2). The matching procedure is conceptually similar to absolute magnitude estimation, whereby subjects match their impression of number size to their impression of the subjective magnitude of a stimulus. In Experiment 1, subjects matched their impression of the stimulus to their impression of the magnitude of the length of a continuously variable line under their control. In Experiment 2, subjects rated perceived sweetness on a vertical 13-point scale with five equally spaced verbal labels. In both experiments, three sets of four sucrose concentrations were employed. In two of these sets, a set of weaker solutions and a set of stronger solutions, concentrations were separated by 0.25 log units. In a third set, which spanned the range of concentrations used in the other two sets (0.87 to 27.36% w/v), solutions were separated by 0.5 log units. An examination ofboth individual and group data showed the matching procedure to be less susceptible to a range bias than the rating procedure. In particular, a single intensity function accommodated data from individual ranges better when the matching procedure was used than when the rating procedure was used. No effect of stimulus spacing was evident in the data from either procedure.