Contextual effects in the perception of quinine HCl/NaCl mixtures

Stimulus distribution, stimulus spacing and stimulus range affectmean intensity ratings of solutions of unmixed tastants. Thepresent study compares contextual effects for mixture ratingswith those for unmixed stimuli: if ratings for mixed and unmixedstimuli are differentially affected by context, the degree ofmixture suppression inferred from the responses is context-dependent.Bitterness intensity ratings for unmixed quinine and quinineHCl/NaCl mixtures were not differentially affected by shiftsin stimulus frequency distribution. The subjects' tendency tobe consistent in their responses to identical stimuli, resultsin a transfer of stimulus context of previous sessions to thenext.     

A comparison of different methods used to assess sensitivity to the taste of phenylthiocarbamide (PTC)

Four methods for assessing sensitivity to the bitterness ofphenylthiocarbamide (PTC) and propylthiouracil (PROP) were compared.Good agreement was found among results from forcedchoice detectionthresholds, recognition thresholds, and category ratings ofsingle stimuli. Testing by means of papers impregnated withthese compounds led to a high incidence of false positive responsesfrom insensitive subjects. Phenylthiocarbamide was a slightlybetter discriminator of sensitive from insensitive subjectsthan was propythiouracil. Category ratings of the intensityof the antimodal PTC threshold concentration are a valid, reliableand efficient screening method. Relative safety in the use ofPTC and PROP is discussed.     

INDUCTION OF SCALING ERRORS

Judges were required to rate the total intensity of NaCl solutions using a variety of unstructured category and line scales under a 'rank-rating' protocol and a traditional protocol that did not allow retasting or the reviewing of scores. The various scales and protocols induced two types of scaling errors. The first type was named a different-stimulus error. This involved a judge rating a stronger stimulus as equal to or less than a weaker stimulus. The second type was named a same-stimulus error. This involved a judge giving different ratings to two stimuli of equal concentration. For all scales, judges made a higher proportion of same-stimulus errors than different-stimulus errors. 'Rank-rating' only reduced the proportion of different-stimulus errors. It was hypothesized that a category scale with fewer categories would induce a higher level of different-stimulus errors but lower level of same-stimulus errors. These trends were noted but not always significantly. For line scales, the equivalent hypotheses regarding line length were either weak or not supported. It would appear that increasing the length of a line scale is not always equivalent to increasing the number of categories in a category scale.     

CONTEXTUAL SHIFTS IN HEDONIC JUDGMENTS

Taste intensity ratings are higher when many low-intensity stimuli are presented than when many high-intensity stimuli are presented. It is investigated whether similar contextual shifts occur for hedonic judgments. Experiment 1 assessed the perceived pleasantness of a heterogeneous stimulus set containing either a large number of quinine (unpleasant context) or sucrose (pleasant context) solutions. In Experiment 2 subjects made hedonic judgments for a set of sucrose solutions. They were classified pre-experimentally as ‘sweet-likers,’‘neutrals,’ or ‘sweet-dislikers.’ Stimulus frequency distributions were positively or negatively skewed. In Experiment 1, hedonic ratings in the pleasant context were lower than those obtained in the unpleasant context. In Experiment 2, no effect of stimulus context was found. It is argued that contextual shifts in hedonic judgments are found only if the stimuli differ substantially along the hedonic dimension. In addition, the subject groups should be homogeneous with regard to preference rank orders, and should be sufficiently large to allow testing with adequate statistical power.     

Influence of method of reporting study results on decision of physicians to prescribe drugs to lower cholesterol concentration.

OBJECTIVE--To determine whether the reporting of study results by using reductions in relative or absolute risk and the number needed to treat affects the views of physicians about the effectiveness of drugs to lower lipid concentrations and decisions about treatment. DESIGN--Random allocation of two questionnaires presenting the results of three end points of the Helsinki heart study as results from separate trials by using reduction in either relative or absolute risk. In both questionnaires one end point was also presented by showing person years of treatment needed to prevent one myocardial infarction. The effectiveness of lipid lowering drugs was assessed for all end points on an 11 point scale. For each study result the likelihood to treat hypercholesterolaemia of 7.5 mmol/l in a healthy man had to be indicated on a seven point scale. SUBJECTS--Random sample of 802 internists and general practitioners representative of providers of primary care in Switzerland. RESULTS--The response rate was 69.6% (558). For the prevention of fatal and non-fatal myocardial infarction the mean ratings of effectiveness of lipid lowering drugs were 0.45 (95% confidence interval 0.21 to 0.69) and 1.39 (1.09 to 1.68) scale points lower when the reduction of absolute risk or number needed to treat were reported instead of the relative risk reduction (both P < 0.001). Physicians receiving trial results for identical end points in form of absolute reduction of risk or number needed to treat were less inclined to treat hypercholesterolaemia (both P < 0.001). CONCLUSIONS--Physicians'' views of the effectiveness of lipid lowering drugs and the decision to prescribe such drugs is affected by the predominant use of reduction of relative risk in trial reports and advertisements.     

Sexual Conflict and Gender Gap Effects: Associations between Social Context and Sex on Rated Attractiveness and Economic Status

Human mate choice research often concerns sex differences in the importance of traits such as physical attractiveness and social status. A growing number of studies indicate that cues to social context, including other people who appear in stimulus photographs, can alter that individual’s attractiveness. Fewer studies, however, consider judgements of traits other than physical attractiveness, such as wealth. Here we manipulate the presence/absence of other people in photographs of target models, and test the effects on judgments of both attractiveness and earnings (a proxy for status). Participants (N = 2044) rated either male or female models for either physical attractiveness or social/economic status when presented alone, with same sex others or with opposite sex others. We collectively refer to this manipulation as ‘social context’. Male and female models received similar responses for physical attractiveness, but social context affected ratings of status differently for women and men. Males presented alongside other men received the highest status ratings while females presented alone were given the highest status ratings. Further, the status of females presented alongside a male was constrained by the rated status of that male. Our results suggests that high status may not directly lead to high attractiveness in men, but that status is more readily attributed to men than to women. This divide in status between the sexes is very clear when men and women are presented together, possibly reflecting one underlying mechanism of the modern day gender gap and sexist attitudes to women’s economic participation. This adds complexity to our understanding of the relationship between attractiveness, status, and sex in the light of parental investment theory, sexual conflict and economic theory.     

Acquired inversions in human leucocytes

Peri- and paracentric inversions are observed in human leukocytes at various rates. Four categories are proposed, in relation to the frequency of occurrence, although it may vary with time for a same inversion. Category 1 corresponds to isolated, thus non recurrent inversions. Category 2 (f congruent to .001) corresponds to inv(14)(q12qter) and inv(7)(p14q35) in individuals with presumably normal genetic constitution. Category 3 (f congruent to .01) corresponds to inv(7)(p14q35) in patients affected by ataxia telangiectasia (AT). This inversion, when it is frequent, indicates an abnormal genetic constitution, radiation sensitive and predisposing to cancers. Finally, category 4 (f greater than or equal to .1) corresponds to inversions existing in precancer or in cancer clonal cells: inv(14)(q11.2q32.2) in AT patients affected by a T-cell hemopathy, inv(14)(q12qter) in chronic T-cell lymphocytic leukaemia, and inv(16)(p13q22) in acute myelomonocytic leukaemia with abnormal eosinophils. The prognostic and diagnostic interests of these inversions is discussed.     

Taste function in patients with oral burning

Burning mouth syndrome (BMS) is an oral pain disorder occurring primarily in post-menopausal women and is frequently accompanied by taste complaints. This association of symptoms suggests an interaction between the mechanisms of nociception and gustation, two senses with strong hedonic components. Seventy-three patients of the Taste and Smell Clinic at the University of Connecticut Health Center who reported experiencing 'unexplained oral burning' were evaluated for taste function. Both intensity ratings and quality identifications were measured for a concentration series of sucrose ('sweet'), NaCl ('salty'), citric acid ('sour') and quinine-HCl ('bitter'). The 57 women with BMS gave lower intensity ratings to NaCl and sucrose than comparably aged, same sex controls. Concentrations of NaCl and sucrose >0.10 M were most affected; concentrations of sucrose and NaCl <0.10 M were rated similarly by BMS and control women. No intensity differences were found for citric acid or quinine-HCl at any concentration and no differences were evident between the 16 BMS men and the 14 control men for any stimulus. The BMS women also misidentified the quality of 19% of the stimuli that were detected whereas control women misidentified 8%. Both groups detected a similar proportion of stimuli and found lower stimulus concentrations more difficult to identify than higher concentrations. Identification of NaCl as 'salty' and citric acid as 'sour' was particularly difficult for BMS women. The present findings are consistent with the hypothesis that pain pathway activation may affect neural and behavioral taste function.     

Strategy of auditory discrimination of scale in Java sparrows: they use both "imagery" and specific cues

We examined whether Java sparrows use imagery of auditory stimuli (imagery is a subject's mental representation of a stimulus by which the subject's behaviour may be governed under stimulus control even in the absence of the physical stimulus). Three types of ascending tone sequences were used. In the intact scale, sequence tones were played in ascending order. In the intact-masked scale, part of the sequence was masked by noise but the remaining scale was identical with the intact scale, whereas in the violated scale, the sequence could be heard as if tones were played slowly (Experiment 1) or quickly (Experiment 2). Subjects were divided into two groups: one group was trained to respond to the intact and intact-masked scales and to suppress response to the violation scale (imagery-positive group). The contingency was reversed for the other (violation-positive) group. In Experiment 1, all the birds acquired discrimination, but successful transfer to novel stimuli was observed only in the imagery-positive group, suggesting that the imagery of the tone sequence was used as a discriminative cue. Experiment 2 confirmed that the stimulus duration was a discriminative cue for both groups, suggesting that the birds also acquired discrimination using only specific cues.     

Laboratory conditioning to still or flowing water does not affect the responses to a food stimulus by red swamp crayfish (Procambarus clarkii) in flowing water habitats

We tested the role of hydrodynamics in the use of chemical signals by the red swamp crayfish (Procambarus clarkii). We conditioned the crayfish in either a still water or flowing water habitat for 2 weeks. We then observed the crayfish in control (no stimulus) and experimental (food stimulus) trials in one of two flowing water habitats-laminar or turbulent. Habitat use was significantly different between control and experimental observations, but there was no effect of conditioning habitat or experimental habitat on the responses to the food stimulus. This study adds to a growing body of literature consistent with the idea that gross responses to chemical stimuli in crayfish are not affected by the hydrodynamic context in which they are encountered.     

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) from the freshwater stingray Himantura chaophraya (Batoidea: Dasyatidae) in Malaysian Borneo

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) are described from the spiral intestine of the Freshwater whipray, Himantura chaophraya, in the Kinabatangan River in Malaysian Borneo. Based on criteria set forth in a previous categorization scheme for species of Acanthobothrium, these consist of 3 Category 1 species, Acanthobothrium asnihae n. sp., Acanthobothrium saliki n. sp., and Acanthobothrium zainali n. sp.; a Category 8 species, Acanthobothrium etini n. sp.; and a Category 2 species, Acanthobothrium masnihae n. sp.. Acanthobothrium asnihae n. sp. differs from all Category 1 species in its possession of a horizontal band of weak musculature that divides the posterior loculus in half. Among Category 1 species, A. saliki n. sp. differs from all but Acanthobothrium southwelli in its possession of postovarian testes. It differs from A. southwelli in its possession of fewer testes and a greater number of proglottids. Acanthobothrium zainali n. sp. differs from the 25 other Category 1 species in a combination of overall size, muscular pad and hook shape, arrangement and number of testes, ovary configuration in cross section, position of ovarian isthmus, and genital pore position. Acanthobothrium etini n. sp. is distinguished from all 5 other Category 8 species in its lack of testes from the proglottid antiporal and postporal regions and in testis number. Acanthobothrium masnihae n. sp. differs from the 35 other Category 2 species in its possession of fewer testes, postporal testes, or a greater number of proglottids. A key to Acanthobothrium species parasitizing H. chayophraya is presented. This represents the first report of Acanthobothrium from freshwater stingrays belonging to a family other than the Potamotrygonidae.     

Sound representation methods for spectro-temporal receptive field estimation

The spectro-temporal receptive field (STRF) of an auditory neuron describes the linear relationship between the sound stimulus in a time-frequency representation and the neural response. Time-frequency representations of a sound in turn require a nonlinear operation on the sound pressure waveform and many different forms for this non-linear transformation are possible. Here, we systematically investigated the effects of four factors in the non-linear step in the STRF model: the choice of logarithmic or linear filter frequency spacing, the time-frequency scale, stimulus amplitude compression and adaptive gain control. We quantified the goodness of fit of these different STRF models on data obtained from auditory neurons in the songbird midbrain and forebrain. We found that adaptive gain control and the correct stimulus amplitude compression scheme are paramount to correctly modelling neurons. The time-frequency scale and frequency spacing also affected the goodness of fit of the model but to a lesser extent and the optimal values were stimulus dependant. Action Editor: Israel Nelken     

Optimal stimulation settings for CMAP scan registrations

Background

The CMAP (Compound Muscle Action Potential) scan is a non-invasive electrodiagnostic tool, which provides a quick and visual assessment of motor unit potentials as electrophysiological components that together constitute the CMAP. The CMAP scan records the electrical activity of the muscle (CMAP) in response to transcutaneous stimulation of the motor nerve with gradual changes in stimulus intensity. Large MUs, including those that result from collateral reinnervation, appear in the CMAP scan as so-called steps, i.e., clearly visible jumps in CMAP amplitude. The CMAP scan also provides information on nerve excitability. This study aims to evaluate the influence of the stimulation protocol used on the CMAP scan and its quantification.

Methods

The stimulus frequency (1, 2 and 3 Hz), duration (0.05, 0.1 and 0.3 ms), or number (300, 500 and 1000 stimuli) in CMAP scans of 23 subjects was systematically varied while the other two parameters were kept constant. Pain was measured by means of a visual analogue scale (VAS). Non-parametric paired tests were used to assess significant differences in excitability and step variables and VAS scores between the different stimulus parameter settings.

Results

We found no effect of stimulus frequency on CMAP scan variables or VAS scores. Stimulus duration affected excitability variables significantly, with higher stimulus intensity values for shorter stimulus durations. Step variables showed a clear trend towards increasing values with decreasing stimulus number.

Conclusions

A protocol delivering 500 stimuli at a frequency of 2 Hz with a 0.1 ms pulse duration optimized CMAP scan quantification with a minimum of subject discomfort, artefact and duration of the recording. CMAP scan variables were influenced by stimulus duration and number; hence, these need to be standardized in future studies.     

Relationships among taste qualities assessed with response-context effects

Psychophysical judgments often depend on stimulus context. For example, sugar solutions are judged sweeter when a tasteless fruity aroma has been added. Response context also matters; adding a fruity aroma to sugar increases the rated sweetness when only sweetness is considered but not when fruitiness is judged as well. The interaction between stimulus context and response context has been explored more extensively in taste-odor mixtures than in taste-taste mixtures. To address this issue, subjects in the current study rated the sourness of citric acid mixed with quinine (bitter), sodium chloride (salty), and cyclamate (sweet) (stimulus context). In one condition, subjects rated sourness alone. In another, subjects rated both sourness and the other salient quality (bitterness, saltiness, or sweetness) (response context). Sourness ratings were most sensitive to response context for sour-salty mixtures (i.e., ratings of sourness alone exceeded ratings of sourness made simultaneously with saltiness) and least sensitive to context for the sour-sweet mixtures (sourness ratings made under the 2 conditions were essentially identical). Response-context effects for the sour-bitter mixture were nominally intermediate. The magnitudes of these context effects were related to judgments of qualitative similarity between citric acid and the other stimuli, consistent with prior findings. These types of context effects are relevant to the study of taste-taste mixture interactions and should provide insight into the perceptual similarities among the taste qualities.     

Calcium carbonate scale formation and control

This paper focuses on the complex problem of calcium carbonate scale formation on heated surfaces and the possibilities of controlling or reducing this problem. The development of scale is a multistage process and is affected by a number of factors, these include supersaturation, pH, temperature and flow velocity. Calcium carbonate deposition can be ameliorated by chemical, physical or biological methods with various level of effectiveness. These controls can be divided into three main categories: those that affect solubility, those that alter the growth mechanism of crystals, and those that change the potential of a surface to foul. One of the most effective methods of controlling crystallization fouling is the addition of chemical inhibitors to potentially scaling waters. There are a number of alternative non-chemical treatment options available, amongst these are the use of magnetic, electronic and electrolytic treatment devices. Scale formation is affected by the physical nature of the material on which it is forming, therefore it is possible to choose material to reduce scale formation. Each of these scale controlling methods has their advantages and a number of factors have to be considered before choosing the right option.     

Bivariate cumulative probit model for the comparison of neuronal encoding hypotheses

Understanding the way stimulus properties are encoded in the nerve cell responses of sensory organs is one of the fundamental scientific questions in neurosciences. Different neuronal coding hypotheses can be compared by use of an inverse procedure called stimulus reconstruction. Here, based on different attributes of experimentally recorded neuronal responses, the values of certain stimulus properties are estimated by statistical classification methods. Comparison of stimulus reconstruction results then allows to draw conclusions about relative importance of covariate features. Since many stimulus properties have a natural order and can therefore be considered as ordinal, we introduce a bivariate ordinal probit model to obtain classifications for the combination of light intensity and velocity of a visual dot pattern based on different covariates extracted from recorded spike trains. For parameter estimation, we develop a Bayesian Gibbs sampler and incorporate penalized splines to model nonlinear effects. We compare the classification performance of different individual cell covariates and simple features of groups of neurons and find that the combination of at least two covariates increases the classification performance significantly. Furthermore, we obtain a non‐linear effect for the first spike latency. The model is compared to a naïve Bayesian stimulus estimation method where it yields comparable misclassification rates for the given dataset. Hence, the bivariate ordinal probit model is shown to be a helpful tool for stimulus reconstruction particularly thanks to its flexibility with respect to the number of covariates as well as their scale and effect type.     

Visual stimuli in distraction strategies for increasing pain tolerance. The confounding of affect with other stimulus characteristics

Recent experimental studies in pain control have questioned the value of pleasant affect in strategies employing distraction. It appears that pleasant affect may have been systematically confounded with task complexity or novelty in past research that found pleasant imagery or slides effective in increasing pain tolerance with the cold pressor test. The present study was a follow-up to a study conducted by this author (Greenstein, 1984) in which unpleasant slides had significantly increased pain tolerance above pleasant slide level. In the present study, 69 college students (35 females, 34 males) rated either the pleasant or unpleasant slides used in the original study on their perceived pleasantness, complexity, and uniqueness (novelty). Results indicated that the unpleasant slides were rated significantly more complex (P less than 0.001) and unique (P less than 0.001) than the pleasant slides. Additionally, as in the earlier study, ratings of the unpleasant slides on pleasantness deviated significantly farther from neutrality than did ratings of the pleasant slides (t = 5.04, P less than 0.001). Thus the unpleasant slides were also perceived as being more significant (i.e., pertinent) than were the pleasant slides. The results indicate that affect was confounded with other stimulus characteristics in the Greenstein (1984) pain control study and probably in a significant number of other studies as well. Researchers are cautioned to control for the stimulus characteristics of visual distraction strategies used in pain control studies. The assumption that pleasantness, per se, contributes to strategy effectiveness is no longer tenable; future research must demonstrate an independent effect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Validation of a handheld display device for an expandable labeled magnitude scale (LMS)

Palmtop computers provide a possible avenue for the convenient collection of subjective ratings from individuals outside of a fixed laboratory setting. One disadvantage of these computers is the small size of their display screens, which may reduce the resolution of responses available as compared with standard display screens. One plausible solution to this problem is to use a scale that expands contingent on an initial response made by the subject, so that the final response is made from a scale with finer resolution. To validate this approach, we compared taste intensity judgments of six sucrose solutions (0.03, 0.06, 0.12, 0.24, 0.48, and 0.96 M), using a labeled magnitude scale either presented in expandable form on a palmtop computer (Palm scale) or in conventional (nonexpandable) form on a standard 17' PC monitor (PC scale). Twenty-four subjects rated all six sucrose solutions thrice, using both scale types, the different scales being used on different days of testing. The scales led to very similar taste intensity ratings at all but the lowest concentration, which was rated less intense on the Palm scale. The Palm scale was used with slightly less precision than the PC scale for the weakest solution concentrations. In summary, the responses of the two scales were similar enough to validate the use of the expandable scale on the palmtop computer outside the laboratory setting.     

Predictive Dynamics of Human Pain Perception

While the static magnitude of thermal pain perception has been shown to follow a power-law function of the temperature, its dynamical features have been largely overlooked. Due to the slow temporal experience of pain, multiple studies now show that the time evolution of its magnitude can be captured with continuous online ratings. Here we use such ratings to model quantitatively the temporal dynamics of thermal pain perception. We show that a differential equation captures the details of the temporal evolution in pain ratings in individual subjects for different stimulus pattern complexities, and also demonstrates strong predictive power to infer pain ratings, including readouts based only on brain functional images.     

Summation of perceptual cues in natural visual scenes

Natural visual scenes are rich in information, and any neural system analysing them must piece together the many messages from large arrays of diverse feature detectors. It is known how threshold detection of compound visual stimuli (sinusoidal gratings) is determined by their components' thresholds. We investigate whether similar combination rules apply to the perception of the complex and suprathreshold visual elements in naturalistic visual images. Observers gave magnitude estimations (ratings) of the perceived differences between pairs of images made from photographs of natural scenes. Images in some pairs differed along one stimulus dimension such as object colour, location, size or blur. But, for other image pairs, there were composite differences along two dimensions (e.g. both colour and object-location might change). We examined whether the ratings for such composite pairs could be predicted from the two ratings for the respective pairs in which only one stimulus dimension had changed. We found a pooling relationship similar to that proposed for simple stimuli: Minkowski summation with exponent 2.84 yielded the best predictive power (r=0.96), an exponent similar to that generally reported for compound grating detection. This suggests that theories based on detecting simple stimuli can encompass visual processing of complex, suprathreshold stimuli.