Duration discrimination by musicians and nonmusicians

This study investigated the effects of stimulus modality, standard duration, sex, and laterality in duration discrimination by musicians and nonmusicians. Seventeen musicians (M age = 24.1 yr.) and 22 nonmusicians (M age = 26.8 yr.) participated. Auditory (1,000 Hz) and tactile (250 Hz) sinusoidal suprathreshold stimuli with varying durations were used. The standard durations tested were 0.5 and 3.0 sec. Participants discriminated comparison stimuli which had durations slightly longer and shorter than the standard durations. Difference limens were found by the method of limits and converted to Weber fractions based on the standard durations. Musicians had lower, i.e., better, Weber fractions than nonmusicians in the auditory modality, but there was no significant difference between musicians and nonmusicians in the tactile modality. Auditory discrimination was better than tactile discrimination. Discrimination improved when the standard duration was increased both for musicians and nonmusicians. These results support previous findings of superior auditory processing by musicians. Significant differences between discrimination in the millisecond and second ranges may be due to a deviation from Weber's law and the discontinuity of timing in different duration ranges reported in the literature.     

Amplitude and spatial-period discrimination in sinusoidal gratings by dynamic touch

We measured discrimination thresholds for sinusoidal gratings using active dynamic touch. In the first experiment we measured the thresholds for amplitude discrimination as a function of amplitude and spatial period. Thresholds ranged between 10.8%, and 15.8% of the standard amplitude. We showed that amplitude differences as small as 2 microm can be detected. We found that Weber fractions for amplitude discrimination are constant over a range of amplitudes, but are influenced by the spatial period of the grating; discrimination improved with increasing spatial period. In the second experiment we determined the thresholds for spatial-period discrimination. We used the same design as in the first experiment. Weber fractions ranged from 6.4% to 11.8%. Amplitude was found to have no effect on the Weber fractions for spatial-period discrimination. However, the spatial period had an effect on the Weber fractions: larger spatial periods yielded lower Weber fractions.     

Nested models of relative judgment: Applications to a similarity averaging model

A theoretical analysis of the Eisler and Ekman (1959) model of similarity judgments for unidimensional continua is presented, based on a general model of relative judgment. This general model assumes that judgments are mediated by perceived relations of pairs of stimuli, that there exists a transformation of the judgmental response that is a function of the sensory ratio of the two stimuli, and that response bias operates in a multiplicative manner. Three structural conditions are presented, each imposing constraints on the structure of observed judgments. The structural conditions define threenested models of relative judgment, with the second a weakened version of the first, and the third a weakened version of the second. The special virtue of the general model is that it is applicable to a variety of judgmental tasks (e.g., ratio estimation, similarity, pair comparison), the key being derivation of theresponse transformation conforming to the structural conditions. The structural conditions thus constitute necessary conditions for several different judgmental models. The theory was first applied with success to ratio estimation judgments (Fagot, 1978), and this paper applies the general model to the Eisler and Ekman similarity “averaging” model. Empirical tests were carried out on published data for pitch, darkness, visual area, and heaviness judgments. Although the strong form of the model presented by Eisler and Ekman was rejected, weakened versions were generally supported by the data. These results were similar to those obtained for ratio estimation (Fagot, 1978), and are interpreted to be very promising for the general model of relative judgment.     

When are semantic targets detected faster than visual or acoustic ones?

Duration-discrimination data from an experiment using empty auditory intervals in a two-alternative forced-choice paradigm are presented. The observed functional relationship between standard deviation of the psychometric density function and stimulus duration is shown to be fit significantly better by a Weber’s law model of duration discrimination than by Creelman’s counter model. Both models fail to predict the rapid rise in the Weber fraction observed for durations longer than about 2 sec. However, the Weber’s law model, based on a generalization of Weber’s law, accurately predicts the initial drop in the Weber fraction for very short durations and the observed constancy of the Weber fraction for durations up to 2 sec.     

Vibro-tactile and visual asynchronies: sensitivity and consistency

We investigated the consistency between tactually and visually designated empty time intervals. In a forced-choice discrimination task, participants judged whether the second of two intervals was shorter or longer than the first interval. Two pulses defined the intervals. The pulse was either a vibro-tactile burst presented to the fingertip, or a foveally presented white square. The comparisons were made for uni-modal and cross-modal intervals. We used four levels of standard interval durations in the range of 100- 800 ms. The results showed that tactile empty intervals must be 8.5% shorter to be perceived as long as visual intervals. This cross-modal bias is larger for small intervals and decreases with increasing standard intervals. The Weber fractions (the threshold divided by the standard interval) are 20% and are constant over the standard intervals. This indicates that the Weber law holds for the range of interval lengths tested. Furthermore, the Weber fractions are consistent over uni-modal and cross-modal comparisons, which indicates that there is no additional noise involved in the cross-modal comparisons.     

Human performance on an analogue of an interval bisection task

Two experiments used normal adult human subjects in an analogue of a time interval bisection task frequently used with animals. All presented durations were defined by the time between two very brief clicks, and all durations were less than 1 sec, to avoid complications arising from chronometric counting. In Experiment 1 different groups of subjects received standard durations of either 0.2 and 0.8 or 0.1 and 0.9 sec and then classified a range of durations including these values in terms of their similarity to the standard short (0.2- or 0.1-sec) and long (0.8- or 0.9-sec) durations. The bisection point (defined as the duration classified as "long" on 50% of trials) was located at 0.43 sec in the 0.2-0.8 group, and at 0.46 sec in the 0.1-0.9 group. Experiment 2 replicated Experiment 1 using a within-subject procedure. The bisection point of both 0.2- and 0.8 sec and 0.1- and 0.9-sec durations was found to be 0.44 sec. Both experiments thus found the bisection point to be located at a duration just lower than the arithmetic mean of the standard short and long durations, rather than at the geometric mean, as in animal experiments. Some other performance measures, such as difference limen, and Weber ratio, were, however, of similar values to those found in bisection tasks with animals. A theoretical model assuming that humans bisect by taking the difference between a presented duration and the short and long standards, as well as having a bias to respond "long", fitted the data well. The model incorporated scalar representations of standard durations and thus illustrated a way in which the obtained results, although different from those found with animal subjects, could be reconciled with scalar timing theory.     

Frequency of occurrence as a psychophysical continuum: Weber’s fraction,Ekman’s fraction,range effects,and the phi-gamma hypothesis

Using the continuum of frequency of occurrence of words in English, it was found that: (1) errors in judgment are distributed lognormally rather than normally, and therefore the standard method of calculating Weber’s fraction underestimates its definition, (2) Weber’s fraction has an extremely large value of 3.3, (3)Ekman’s fraction equals 1.81, not .03 as with sensory continua, and (4)the logarithm of the dynamic range times Stevens’ law exponent equals 3.83, not 1.53 as with sensory continua. The last two results favor Teghtsoonian’s underlying sensory scale interpretation over Poulton’s range effects interpretation of the range-exponent relation.     

Psychophysical functions for active tactual discrimination of line width by blind children

Two psychophysical experiments were conducted on active tactual discrimination of line width using the method of constant stimuli with blind subjects. In Experiment I, 93 subjects made single judgments over each of five standards between 0.04 and 0.12 in. In Experiment II, 6 subjects were tested repeatedly over seven standards between 0.04 and 0.50 in. Over the range of standards common to both experiments, the Weber fractions decreased as the width of the standard increased. For two larger standards (0.25 and .50 in.), the Weber fractions approached asymptote and then increased respectively suggesting a U-shaped function. No differences in accuracy of discrimination were found between males vs. females, age groupings, or grade groupings.     

Discrimination thresholds for haptic perception of volume, surface area, and weight

The present study investigated the human ability to discriminate the size of 3-D objects by touch. Experiment 1 measured the just noticeable differences (JNDs) for three tasks: (1) discrimination of volume without availability of weight information, (2) discrimination of volume with weight information available, and (3) discrimination of surface area. Stimuli consisted of spheres, cubes, and tetrahedrons. For all shapes, two reference sizes were used (3.5 and 12 cm(3)). No significant effect of task on the discriminability of objects was found, but the effects of shape and size were significant, as well as the interaction between these two factors. Post hoc analysis revealed that for the small reference, the Weber fractions for the tetrahedron were significantly larger than the fractions for the cube and the sphere. In Experiment 2, the JNDs for haptic perception of weight were measured for the same objects as those used in Experiment 1. The shape of objects had no significant effect on the Weber fractions for weight, but the Weber fractions for the small stimuli were larger than the fractions for the large stimuli. Surprisingly, a comparison between the two experiments showed that the Weber fractions for weight were significantly larger than the fractions for volume with availability of weight information. Taken together, the results reveal that volume and weight information are not effectively combined in discrimination tasks. This study provides detailed insight into the accuracy of the haptic system in discriminating objects' size. This substantial set of data satisfies the need for more fundamental knowledge on haptic size perception, necessary for a greater understanding of the perception of related properties, as well as of more general perceptual processes.     

The discriminability of remembered magnitudes

Psychometric functions and the associated indices of discriminative performance (i.e., the point of subjective equality [PSE], just noticeable difference, and Weber fraction) were obtained with the method of constant stimuli using perceptual and remembered line-length standards. Three important results were obtained. First, comparisons with a perceptual or a remembered standard were sensitive to variations of absolute stimulus differences with a common ratio; that is, Weber's law was violated. Second, relative to discriminative performance with the longest and shortest remembered standards, comparisons involving mid-range remembered standards displayed increased variability in the PSE and inflated Weber fractions, characteristic of a reduction in the quality of the memorial representation. Finally, large and negative time-order errors (TOE) were observed for successive line judgments but not for those involving remembered standards. The implications of these findings for research concerned with the relationships between perception and memory, as well as the TOE phenomenon, are discussed.     

ON PSYCHOPHYSICS IN GENERAL AND THE GENERAL PSYCHOPHYSICAL DIFFERENTIAL EQUATION IN PARTICULAR

The first part of the paper discusses theoretical issues regarding the problem of measurement in psychophysics and the suitable choice of a subjective scale, with special reference to the views of Ekman, Ross, Suppes & Zinnes, and Treisman. The theory of the GPDE is discussed more fully than before. In the second part, further empirical confirmation of the GPDE is given for the following combinations of Weber functions: constant-constant, linear-linear, linear-parabolic, parabolic-parabolic.     

Weber fractions for weight and mass as a function of stimulus intensity

Laboratory simulations of weightlessness have shown that the Weber fraction for mass is higher than that for weight in the range 1000-7000 g. Experiments in the weightless conditions of orbital and parabolic flight have found the same at the 50 g level. To obtain measures at intermediate intensities, the Weber fractions for weight and mass were measured for 15 subjects at 50, 200 and 400 g. The stimuli were canisters suspended on strings. The subjects lifted them for the weight condition and swung them firmly sideways for the mass condition. The Weber fraction was higher for mass than for weight at all intensities, and increased at 50 g for both conditions. In a second mass condition, in which the subjects shook the cylinders within a loosely clenched hand, the Weber fraction remained almost constant at all intensities and was significantly smaller than for the firm swing method at 50 g. The differences in performance between conditions may be related to the continuity or intermittency of pressure information. Other explanations are discussed.     

Semantic control of eye movements in picture scanning during sentence-picture verification

The Weber fraction, (I + Δ)/I, was measured for pure tones which were I presented either homophasically or antiphasically. For both stimuli, the Weber fraction was measured as a function of changes in the level of the standard tone Iand in the phase angle of addition between a test tone and the standard tone. The value, ΔI, in the Weber fraction was defined as that difference between the level of the test-plus-standard and the level of the standard (I) which was required for the listener to discriminate a difference between the standard and the test-plus-standard. In the homophasic case, the Weber fraction remained constant for changes in the phase angle of addition, whereas in the antiphasic condition, the Weber fraction decreased for increasing values of the phase angle of addition. For both the homophasic and antiphasic conditions and at all values of the phase angle of addition, the Weber fraction remained a constant as the value of the standard was varied. These results are in agreement with those obtained in studies involving noise masking, lateralization, and the monaural Weber fraction.     

The effects of duration,area, and background intensity on the visual intensity difference threshold given by the forced-choice procedure: Derivations from a statistical decision model for sensory discrimination

A model for visual discrimination is outlined. This assumes that detection is based on separating signaland noise by means of a statistical decision procedure, and that the noise arises from physical and biological sources. When the model is applied to such traditional detection procedures as the method of constant stimuli, it successfully predicts the laws of spatial and temporal summation and the form of the Weber function. The model is extended to the forced-choice procedures. It is found that it predicts departures from the classical laws for spatial and temporal summation and an increase in the slope of the Weber function when the pulsed forced-choice procedure is used, and data are presented that agree with the predictions. It is shown that data obtained with forced choice against a continuous background are consistent with the assumption that the Seither covertly detects or fails to detect an increment at each ofthe two alternative locations and this determines his final overt response, rather than that he directly compares the inputs at the two locations. A comparison between results obtained with the forced-choice procedure with a pedestal, or with the continuous forced-choice procedure, provides further evidence that Ss employ a double detection strategy in the latter case.     

Differences in the acuity of the Approximate Number System in adults: The effect of mathematical ability

It is largely admitted that processing numerosity relies on an innate Approximate Number System (ANS), and recent research consistently observed a relationship between ANS acuity and mathematical ability in childhood. However, studies assessing this relationship in adults led to contradictory results. In this study, adults with different levels of mathematical expertise performed two tasks on the same pairs of dot collections, based either on numerosity comparison or on cumulative area comparison. Number of dots and cumulative area were congruent in half of the stimuli, and incongruent in the other half. The results showed that adults with higher mathematical ability obtained lower Weber fractions in the numerical condition than participants with lower mathematical ability. Further, adults with lower mathematical ability were more affected by the interference of the continuous dimension in the numerical comparison task, whereas conversely higher-expertise adults showed stronger interference of the numerical dimension in the continuous comparison task. Finally, ANS acuity correlated with arithmetic performance. Taken together, the data suggest that individual differences in ANS acuity subsist in adulthood, and that they are related to mathematical ability.     

Interval production as an analogue of the peak procedure: Evidence for similarity of human and animal timing processes

Humans subjects repeatedly produced durations ranging from 0.5 to 1.3 sec, with each trial being followed by accurate feedback as to the time produced. An analogy was drawn between this production task and the peak procedure, a technique used to examine temporal control in rats which typically produces data conforming to scalar timing theory. Human production data were analysed in a way similar to that employed in peak procedure experiments. Using non-linear regression, it was found that the peak of relative frequency distributions of times produced varied accurately with the target time, and that the coefficient of variation of fitted curves was approximately constant as peak location and target time varied. In both these respects human production data were very similar to those collected from rats in peak procedure experiments, and thus compatible with scalar timing and Weber's law. Weber fractions obtained in this experiment were about half the value of those produced by rats in peak procedure studies, but only slightly lower than those obtained from animals in some other experimental situations.     

Intraindividual consistencies in cross-modal matching across several continua

To determine the relationship between individual exponents for cross-modal stimulus matches for both directions of matching, and to assess the transitivity of individual exponents, subjects were asked to adjust both the judgment and criterion stimuli. Experiment 1 involved four continua paired in 12 ordered combinations; Experiment 2 involved five continua and 20 ordered combinations. Two subjects served in each experiment. The individual exponent of the power function for matches of A to B was close to the inverse of the exponent for matches of B to A, but there was systematic deviation, indicating the presence of a small regression effect. Transitivity of individual exponents was determined by forming ratios of exponents from matches involving other continuum pairs to predict obtained exponents; the means of the distribution of deviations of obtained from predicted values was ?.02 log units, and the standard deviation was .15 log units, indicating that, on the average, predicted values were close to obtained exponents—that is, transitivity of exponents holds for individuals.     

Haptic perception of wetness

In daily life, people interact with textiles of different degrees of wetness, but little is known about the mechanics of wetness perception. This paper describes an experiment with six conditions regarding haptic discrimination of the wetness of fabrics. Three materials were used: cotton wool, sponge-structured viscose and thin viscose. Two ways of touching were investigated: static touching, in which only thermal cues were available, and dynamic touching, in which additional mechanical cues were available. For dynamic touching, average Weber fractions for discrimination were around 0.3, whereas for static touching, they ranged from 0.34 to 0.63. The results show that people can make use of the additional mechanical cues to significantly improve their discrimination performance. There was no significant difference between Weber fractions for the three materials, showing that wetness can be judged as a separate perceptual quantity, independent of the material.     

On the Construct Validity of Integrity Tests: Individual and Situational Factors as Predictors of Test Performance

Although integrity tests are widely applied in screening job applicants, there is a need for research for examining the construct validity of these tests. In the present study, a theoretical model examining the causes of destructive behavior in organizational settings was used to develop background data measures of individual and situational variables that might be related to integrity test scores. Subsequently, 692 undergraduates were asked to complete these background data scales along with (a) two overt integrity tests – the Reid Report and the Personnel Selection Inventory, and (b) two personality‐based measures – the delinquency and socialization scales of the California Psychological Inventory. When scores of these measures were correlated with and regressed on the background data scales, it was found that relevant individual variables, such as narcissism and power motives, and relevant situational variables, such as alienation and exposure to negative peer groups, were related to scores on both types of integrity tests. However, a stronger pattern of validity evidence was obtained for the personality‐based measures and, in all cases, situational variables were found to be better predictors than individual variables. The implications of these findings for the validity of inferences drawn from overt and personality‐based integrity tests are discussed.