Charles S. Watson

User analysis in HCI—the historical lessons from individual differences research

Abstract User analysis is a crucial aspect of user-centered systems design, yet Human–Computer Interaction (HCI) has yet to formulate reliable and valid characterizations of users beyond gross distinctions based on task and experience. Individual differences research from mainstream psychology has identified a stable set of characteristics that would appear to offer potential application in the HCI arena. Furthermore, in its evolution over the last 100 years, research on individual differences has faced many of the problems of theoretical status and applicability that are common to HCI. In the present paper, the relationship between work in cognitive and differential psychology and current analyses of users in HCI is examined. It is concluded that HCI could gain significant predictive power if individual differences research was related to the analysis of users in contemporary systems design.

Factors in the discrimination of tonal patterns. II. Selective attention and learning under various levels of stimulus uncertainty

This is the second in a series of articles in human listeners’ abilities to discriminate between word‐length tonal sequences, or ’’patterns.’’ The first article reported that frequency resolution, by highly trained listeners, is four to five times more accurate for high‐frequency, late‐occurring components of such sequences than for low−frequency early components [Watson, Kelly, and Benbasset, J. Acoust. Soc. Am. 57, 1175–1185 (l975)]. These effects, which are similar to described as ’’recognition masking’’ or ’’informational masking’’ by other authors, have now been shown to be strongly dependent on the degree of trial‐to‐trial stimulus uncertainty of the psychophysical procedure in which they are measured. When stimulus uncertainty is reduced to its psychophysical minimum, frequency resolution for any component of a tonal sequence is only slightly less accurate than for isolated tones. Previous reports of recognition masking this may reflect limitations imposed by those more dynamic parts of the sensory...

Formant-frequency discrimination for isolated English vowels.

Thresholds for formant-frequency discrimination were obtained for ten synthetic English vowels patterned after a female talker. To estimate the resolution of the auditory system for these stimuli, thresholds were measured using well-trained subjects under minimal-stimulus-uncertainty procedures. Thresholds were estimated for both increments and decrements in formant frequency for the first and second formants. Reliable measurements of threshold were obtained for most formants tested, the exceptions occurring when a harmonic of the fundamental was aligned with the center frequency of the test formant. In these cases, unusually high thresholds were obtained from some subjects and asymmetrical thresholds were measured for increments versus decrements in formant frequency. Excluding those cases, thresholds for formant frequency, delta F, are best described as a piecewise-linear function of frequency which is constant at about 14 Hz in the F1 frequency region (< 800 Hz), and increases linearly in the F2 region. In the F2 region, the resolution for formant frequency is approximately 1.5%. The present thresholds are similar to previous estimates in the F1 region, but about a factor of three lower than those in the F2 region. Comparisons of these results to those for pure tones and for complex, nonspeech stimuli are discussed.

Similarity and categorization of environmental sounds

Four experiments investigated the acoustical correlates of similarity and categorization judgments of environmental sounds. In Experiment 1, similarity ratings were obtained from pairwise comparisons of recordings of 50 environmental sounds. A three-dimensional multidimensional scaling (MDS) solution showed three distinct clusterings of the sounds, which included harmonic sounds, discrete impact sounds, and continuous sounds. Furthermore, sounds from similar sources tended to be in close proximity to each other in the MDS space. The orderings of the sounds on the individual dimensions of the solution were well predicted by linear combinations of acoustic variables, such as harmonicity, amount of silence, and modulation depth. The orderings of sounds also correlated significantly with MDS solutions for similarity ratings of imagined sounds and for imagined sources of sounds, obtained in Experiments 2 and 3—as was the case for free categorization of the 50 sounds (Experiment 4)—although the categorization data were less well predicted by acoustic features than were the similarity data.

Performance on frequency‐discrimination tasks by musicians and nonmusicians

Auditory discrimination abilities of professional musicians were compared with those of nonmusicians. The stimuli for the frequency‐discrimination tasks were 300‐msec sinusoidal tones, 300‐msec square waves, and tone patterns consisting of ten 40‐msec tones played sequentially. The musicians’ difference thresholds for single tones were between Δf /f=0.001 and 0.0045. One‐half of the nonmusicians attained thresholds almost as low; the rest attained larger thresholds, up to Δf /f=0.017. The results for the pattern stimuli show a clearer separation between the nonmusicians and musicians, whose median difference thresholds were about three times smaller. However, nonmusician listeners who had previously trained with patterns not in the test set had different thresholds, substantially smaller than those obtained by the musicians. The appropriateness of preferential recruitment of musicians for psychoacoustic research is discussed. The responses to a musical background survey and correlations between the survey...

Individual differences in auditory abilities.

Performance on 19 auditory discrimination and identification tasks was measured for 340 listeners with normal hearing. Test stimuli included single tones, sequences of tones, amplitude-modulated and rippled noise, temporal gaps, speech, and environmental sounds. Principal components analysis and structural equation modeling of the data support the existence of a general auditory ability and four specific auditory abilities. The specific abilities are (1) loudness and duration (overall energy) discrimination; (2) sensitivity to temporal envelope variation; (3) identification of highly familiar sounds (speech and nonspeech); and (4) discrimination of unfamiliar simple and complex spectral and temporal patterns. Examination of Scholastic Aptitude Test (SAT) scores for a large subset of the population revealed little or no association between general or specific auditory abilities and general intellectual ability. The findings provide a basis for research to further specify the nature of the auditory abilities. Of particular interest are results suggestive of a familiar sound recognition (FSR) ability, apparently specialized for sound recognition on the basis of limited or distorted information. This FSR ability is independent of normal variation in both spectral-temporal acuity and of general intellectual ability.

Factors in the discrimination of tonal patterns. I. Component frequency, temporal position, and silent intervals

Factors which determine the discriminability of tonal sequences, or patterns, were investigated in five experiments. The patterns were generally sequences of ten 40‐msec tonal components, which ranged in frequency from 256 to 900 Hz, or from 500 to 1500 Hz, in equi‐log intervals. Highly trained (15 to 60 h of training prior to collecting experimental data) listeners’ abilities to detect changes in the frequency of single tonal components in these patterns were measured using a same–different psychophysical method. The just‐detectable values of Δf (d′=1.0) were only slightly larger than for single 40‐msec tones presented in isolation for tonal components at the end of the temporal sequences (a ’’recency’’ effect). Performance was systematically worse for earlier components, the just‐detectable Δf increasing by four to five times from the end of the pattern to the beginning (no ’’primacy’’ effect). The ’’recency’’ effect was interpreted as a matter of later arriving components interfering with frequency res...

Receiver‐Operating Characteristics Determined by a Mechanical Analog to the Rating Scale

In one portion of a fixed‐interval‐observation experiment, observers indicated their certainty that a 500‐cps signal had been presented in a thermal‐noise background by positioning a slider after each interval. In a second portion of this experiment, the observers responded by making binary decisions. Slider positions were treated as typical confidence ratings; the conditional probability of a given rating or of one indicating greater confidence, given signal plus noise, was plotted against the probability of these ratings, given noise alone. Functions produced in this manner, for a rating scale divided into thirty‐six positions, were fit closely by the receiver‐operating characteristics (ROCs) of the theory of signal detectability. A psychophysical model using two straight‐line segments did not provide a good approximation to these data. Values of d′ were generally lower for the rating procedure than for the binary‐decision procedure. The use of a large number of rating categories did not result in larg...

Masking of Tones by Noise for the Cat

Masked thresholds were obtained by the method of behavioral audiometry fur each of four cats at eleven frequencies over the range from 125 to 16 000 cps. Bands of noise, which were approximately one to two octaves wide, as well as two broad bands of noise, were used as masking stimuli. Experiment I shows that the function relating masking to noise level has exactly the same form for cat as for man; the signal to‐noise ratios, however, are greater for cat than for man. The critical ratio (K) is defined as the ratio of signal power to spectrum level at the masked threshold. The function relating K to frequency was determined for cat in experiment II; tiffs function parallels that for man, but lies 4 to 5 dB above it at most frequencies. The masking data for the cat are shown to be consistent with measurements of frequency discrimination for this animal.

Individual differences in the processing of speech and nonspeech sounds by normal-hearing listeners

While a large portion of the variance among listeners in speech recognition is associated with the audibility of components of the speech waveform, it is not possible to predict individual differences in the accuracy of speech processing strictly from the audiogram. This has suggested that some of the variance may be associated with individual differences in spectral or temporal resolving power, or acuity. Psychoacoustic measures of spectral-temporal acuity with nonspeech stimuli have been shown, however, to correlate only weakly (or not at all) with speech processing. In a replication and extension of an earlier study [Watson et al., J. Acoust. Soc. Am. Suppl. 1 71. S73 (1982)] 93 normal-hearing college students were tested on speech perception tasks (nonsense syllables, words, and sentences in a noise background) and on six spectral-temporal discrimination tasks using simple and complex nonspeech sounds. Factor analysis showed that the abilities that explain performance on the nonspeech tasks are quite distinct from those that account for performance on the speech tasks. Performance was significantly correlated among speech tasks and among nonspeech tasks. Either, (a) auditory spectral-temporal acuity for nonspeech sounds is orthogonal to speech processing abilities, or (b) the appropriate tasks or types of nonspeech stimuli that challenge the abilities required for speech recognition have yet to be identified.