TWO ISSUES IN AUDITORY COGNITION:

Abstract— The study of auditory and music cognition provides opportunities to explore general cognitive mechanisms in a specific, highly structured domain We discuss two problems with implications for other domains of perception the self-organization of perceptual categories and invariant pattern recognition The perceptual category we consider is the octave We show how general principles of self-organization operating on a cochlear spectral representation can vield octave categories The example of invariant pattern recognition we consider is the recognition of invariant frequency patterns transformed to different absolute frequencies We suggest a system that uses pitch or musical key to map tones into a pitch-invariant format.     

Studies in auditory timing: 1. Simple patterns

Listeners' accuracy in discriminating one temporal pattern from another was measured in three psychophysical experiments. When the standard pattern consisted of equally timed (isochronic) brief tones, whose interonset intervals (IOIs) were 50, 100, or 200 msec, the accuracy in detecting an asynchrony or deviation of one tone in the sequence was about as would be predicted from older research on the discrimination of single time intervals (6%-8% at an IOI of 200 msec, 11%-12% at an IOI of 100 msec, and almost 20% at an IOI of 50 msec). In a series of 6 or 10 tones, this accuracy was independent of position of delay for IOIs of 100 and 200 msec. At 50 msec, however, accuracy depended on position, being worst in initial positions and best in final positions. When one tone in a series of six has a frequency different from the others, there is some evidence (at IOI = 200 msec) that interval discrimination is relatively poorer for the tone with the different frequency. Similarly, even if all tones have the same frequency but one interval in the series is made twice as long as the others, temporal discrimination is poorer for the tones bordering the longer interval, although this result is dependent on tempo or IOI. Results with these temporally more complex patterns may be interpreted in part by applying the relative Weber ratio to the intervals before and after the delayed tone. Alternatively, these experiments may show the influence of accent on the temporal discrimination of individual tones.     

Temporal discrimination of recycled tonal sequences: Pattern matching and naming of order by untrained listeners

Sets of recycled sequences of four successive tones were presented in all six possible orders to untrained listeners. For pitches within the musical range, recognition (as measured by matching of any unknown order with an array of permuted orders of the same tones) could be accomplished as readily for tonal durations and frequency separations outside the limits employed for melodic construction as inside these limits. Identifying or naming of relative pitches of successive tones was considerably more difficult than matching for these tonal sequences, and appeared to follow different rules based upon duration and upon frequency separation. Use of frequencies above the pitch limits for music (4,500 Hz and above) resulted in poor performance both for matching and naming of order. Introduction of short silent intervals between items was without effect for both tasks. Naming of order and pattern recognition appear to reflect different basic processes, in agreement with earlier formulations based on experiments with phonemic sequences of speech and sequences of unrelated sounds (hisses, tones, buzzes). Special characteristics of tonal sequences are discussed, and some speculations concerning music are offered.     

The perception of pure and mistuned musical fifths and major thirds: Thresholds for discrimination,beats, and identification

In Experiment 1, the discriminability of pure and mistuned musical intervals consisting of simultaneously presented complex tones was investigated. Because of the interference of nearby harmonics, two features of beats were varied independently: (1) beat frequency, and (2) the depth of the level variation. Discrimination thresholds (DTs) were expressed as differences in level (AL) between the two tones. DTs were determined for musical fifths and major thirds, at tone durations of 250, 500, and 1,000 msec, and for beat frequencies within a range of .5 to 32 Hz. The results showed that DTs were higher (smaller values of ΔL) for major thirds than for fifths, were highest for the lowest beat frequencies, and decreased with increasing tone duration. Interaction of tone duration and beat frequency showed that DTs were higher for short tones than for sustained tones only when the mistuning was not too large. It was concluded that, at higher beat frequencies, DTs could be based more on the perception of interval width than on the perception of beats or roughness. Experiments 2 and 3 were designed to ascertain to what extent this was true. In Experiment 2, beat thresholds (BTs) for a large number of different beat frequencies were determined. In Experiment 3, DTs, BTs, and thresholds for the identification of the direction of mistuning (ITs) were determined. For mistuned fifths and major thirds, sensitivity to beats was about the same. ITs for fifths and major thirds were not significantly different; deviations from perfect at threshold ranged from about 20 to 30 cents. Comparison of the different thresholds revealed that DTs are mainly determined by sensitivity to beats. Detailed analysis, however, indicated that perception of interval width is a relevant aspect in discrimination, especially for the fifths.     

Some experiments relating to the perception of complex tones

Pattern recognition models for the perception of complex tones assume that the pitch of a complex tone is derived from more primary sensations, such as the pitches of the individual partials. Thus a complex tone will only have a well-defined pitch when at least one partial in the complex is separately perceptible. Models based on time-interval measurements, on the other hand, require an interaction of the original components, so that the periodicity of the input waveform is preserved. In Experiment I the relative intensity of a “target” tone, necessary for its identification in the presence of either one or two “masking” tones, was determined, over a range of frequencies. This intensity changes abruptly at around 5 kHz, a result consistent with the idea that the pitches of pure tones are determined by temporal mechanisms for frequencies up to 5 kHz, and by place mechanisms for frequencies above this. In Experiments II and III the audibility of the partials in a multi-tone complex was measured as a function of their frequency separation and compared with the range of conditions over which a complex stimulus produced a clear pitch sensation, using the same set of subjects in each experiment. It was found that under some conditions the complex had a well-defined pitch when none of the individual partials was separately audible. This is contrary to the predictions from the pattern recognition models. The effects of masking noise in the frequency region below the complex, and the results of individual subjects, also did not conform with the predictions from these models. Such models are not ruled out, however, for low harmonic numbers, or for stimuli containing only a small number of partials.     

Interference effects in tone memory

Memory for a standard tone in comparison to a subsequent test tone was examined in three experiments with three intervening tones between the standard and test tones. In each trial, the intervening tones were presented from one of seven frequency range and distance from the standard tone conditions. Experiment 1 tone patterns were played at four different presentation rates, and the subjects judged whether the test was higher or lower than the standard. Memory interference effects caused by the different intervening tone conditions could be accounted for by a directional shift in the standard tone memory toward the intervening tones and by a general decrease in the standard tone memory strength with more distant intervening tones. Interference effects were smaller for the rapid presentation rates because the intervening tones formed separate "perceptual streams." Two additional experiments presented the tone patterns in a task requiring the subjects to match a continuously variable tone to their memory of the standard (Experiment 2) and a task requiring them to judge whether the standard and test tones were the "same" or "different" (Experiment 3). These experiments showed large differences in interference effects as a function of the required judgment and the subjects' musical experience.     

Does stimulus context affect loudness or only loudness judgments?

Marks (1988) reported that when equal-loudness matches were inferred from magnitude estimates of loudness for tones of two different frequencies, the matches were affected by changes in the stimulus intensity range at both frequencies. Marks interpreted these results as reflecting the operation of response biases in the subjects' estimates; that is, the effect of range was to alter subjects' judgments but not necessarily the perception of loudness itself. We investigated this effect by having subjects choose which of two tone pairs defined the larger loudness interval. By using tones of two frequencies, and varying their respective intensity ranges, we reproduced Marks' result in a procedure devoid of numerical responses. When the tones at one frequency are all soft, but the tones at the other frequency are not all soft, cross-frequency loudness matches are different from those obtained with other intensity range combinations. This suggests that stimulus range affects the perception of loudness in addition to whatever effects it may have on numerical judgments of loudness.     

Pattern-directed attention in uncertain-frequency detection

The role of early pattern components as cues in uncertain frequency detection was investigated in four probe-signal experiments. Listeners heard two consecutive presentations of one of two 12-tone patterns in a noise background. One presentation of the pattern was complete, whereas the other was missing the 11th (primary) tone. Listeners were required to indicate which presentation was complete. On 20% of the test trials, the 11th component of the complete pattern was replaced with one of four probe tones. The results indicated that listeners were more sensitive to the primary tone than to probe tones, and this selective sensitivity changed on a trial-by-trial basis as a function of the attentional cues provided by early pattern components. The data suggested two cue functions: (1) an “informational” function in providing information regarding which of two primary tones is likely to occur on a given trial, and (2) a “frequency” function that “automatically” directs listening to an appropriate frequency range and narrows or “fine tunes,” the listening band.     

Frequency ratios and the perception of tone patterns

We quantified the relative simplicity of frequency ratios and reanalyzed data from several studies on the perception of simultaneous and sequential tones. Simplicity of frequency ratios accounted for judgments of consonance and dissonance and for judgments of similarity across a wide range of tasks and listeners. It also accounted for the relative ease of discriminating tone patterns by musically experienced and inexperienced listeners. These findings confirm the generality of previous suggestions of perceptual processing advantages for pairs of tones related by simple frequency ratios.     

Pure-tone perception and ear advantages in dichotic listening

A same-different matching task was used to investigate how subjects perceived a dichotic pair of pure tones. Pairs of stimulus tones in four frequency ranges (center frequencies of 400–1,700 Hz), with separations between 40 and 400 Hzt were tested. Five types of test tones were matched to the stimulus pair: the stimulus pair presented again (control) or crossed over (same tones, different ears), the geometric mean of the two tones, or a binaural tone of the low or high tone of the pair. In the lowest frequency range and the highest with maximum separation, the crossed-over test tones were perceived as different from the same stimulus tones. A bias for perceiving the higher tone of a pair was evident in the frequency ranges with separations of 40-200 Hz. In the lowest frequency range, the bias was for perceiving the higher tone in the right ear. This restricted ear advantage in the perception of pure tones was not significantly related to the right-ear advantage in dichotic word monitoring.     

Perceptual grouping in audition

The present experiments evaluated the effect of relative frequency as a determinant of the figure-ground organization of sequences of auditory tones. Observers counted sequences of 20 ms tones that were presented at the same frequency or that alternated between two different frequencies. The alternating tones differed in frequency by one whole tone, seven tones, or nineteen tones. Counting accuracy increased with increases in the silent interval between the tones. When the alternating tones differed by seven or nineteen tones, counting was disrupted at rates of presentation of eight tones per second or slower. In contrast to this decrement in the counting of tones that alternated by over an octave, very little decrement was observed when the tones alternated by just one whole tone. The best subjects counted these alternating tones more accurately than the tones presented at the same frequency. The poorest subjects showed a small decrement even when the tones alternated by just one whole tone. The results were discussed in terms of determinants of figure-ground organization in auditory information processing.     

Detection of metric structure in auditory figural patterns

This series of experiments dealt with discrimination between two temporal patterns differing only by the insertion of an additional silent gap. In Experiment 1, patterns varied in metric and figural structure. Metric structure is described as the sense of temporal regularity that may occur between subjectively accented tones. Figural structure is described as the grouping of temporally adjacent tones separated by silences. Standard patterns were either strongly or weakly metric; comparison patterns differed from the standards by the insertion of a silence that disrupted either the metric structure alone or both the metric and the figural structures. Experiment 1 provided support for the roles of both metric and figural structures and provided support for the clock-induction model of Povel and Essens (1985) as an account of metric processing. In Experiments 2-4, discrimination of patterns with differing metric structures but identical figural structures was examined more closely. Rate of presentation of the patterns was varied. Multiple regression indicated that, independent of rate variations, discrimination improved as the absolute (not relative) duration of the silent gap increased. We argue that an additional timing mechanism, independent of pattern structure, is operative in temporal pattern discrimination. All the results were replicated across levels of music training of the listeners.     

Variation in performance on auditory and visual monitoring tasks as a function of signal and stimulus frequencies

Observers were required to detect double jumps of a diffuse light spot jumping in a circular pattern and more intense noise pulses in a pulse train. Seven groups performed at different combinations of stimulus and signal frequencies, higher signal frequency/stimulus frequency ratios, and lower stimulus frequencies. Stimulus frequency was a more potent determiner of performance than signal frequency, and performance was not invariant within a given signal frequency/stimulus frequency ratio. Correlations of dependent measures were also examined.-Results are discussed with reference to various theories of vigilance behavior.     

Studies in auditory timing: 2. Rhythm patterns

Listeners discriminated between 6-tone rhythmic patterns that differed only in the delay of the temporal position of one of the tones. On each trial, feedback was given and the subject's performance determined the amount of delay on the next trial. The 6 tones of the patterns marked off 5 intervals. In the first experiment, patterns comprised 3 "short" and 2 "long" intervals: 12121, 21121, and so forth, where the long (2) was twice the length of a short (1). In the second experiment, patterns were the complements of the patterns in the first experiment and comprised 2 shorts and 3 longs: 21212, 12212, and so forth. Each pattern was tested 45 times (5 positions of the delayed tone x 3 tempos x 3 replications). Consistent with previous work on simple interval discrimination, absolute discrimination (delta t in milliseconds) was poorer the longer the intervals (i.e., the slower the tempo). Measures of relative discrimination (delta t/t, where t was the short interval, the long interval, or the average of 2 intervals surrounding the delayed tone) were better the slower the tempo. Beyond these global results, large interactions of pattern with position of the delayed tone and tempo suggest that different models of performance are needed to explain behavior at the different tempos. A Weber's law model fit the slow-tempo data better than did a model based on positions of "natural accent" (Povel & Essens, 1985).     

Effects of context on auditory stream segregation

The authors examined the effect of preceding context on auditory stream segregation. Low tones (A), high tones (B), and silences (-) were presented in an ABA- pattern. Participants indicated whether they perceived 1 or 2 streams of tones. The A tone frequency was fixed, and the B tone was the same as the A tone or had 1 of 3 higher frequencies. Perception of 2 streams in the current trial increased with greater frequency separation between the A and B tones (Delta f). Larger Delta f in previous trials modified this pattern, causing less streaming in the current trial. This occurred even when listeners were asked to bias their perception toward hearing 1 stream or 2 streams. The effect of previous Delta f was not due to response bias because simply perceiving 2 streams in the previous trial did not cause less streaming in the current trial. Finally, the effect of previous ?f was diminished, though still present, when the silent duration between trials was increased to 5.76 s. The time course of this context effect on streaming implicates the involvement of auditory sensory memory or neural adaptation.     

Absolute pitch in boreal chickadees and humans: Exceptions that test a phylogenetic rule

This research examined generality of the phylogenetic rule that birds discriminate frequency ranges more accurately than mammals. Human absolute pitch chroma possessors accurately tracked transitions between frequency ranges. Independent tests showed that they used note naming (pitch chroma) to remap the tones into ranges; neither possessors nor nonpossessors were accurate at octave (pitch height) naming. Boreal chickadees discriminated frequency ranges less accurately than other birds; they tracked reward across several lower frequency ranges but failed at frequencies over 4000 Hz. The results revealed the error of describing species differences solely in terms of their discrimination of frequency ranges. Exceptions to the rule disappear when the rule is restated in terms of underlying mechanism: birds are superior to mammals in the ability to use absolute pitch height perception to discriminate pitches and ranges of pitches.     

元音范畴知觉中特征分析和整合的时间进程

采用启动范式,在三个实验中通过操纵启动音和目标音的频谱相似度和时间间隔,考察了汉语听者元音范畴知觉中特征分析和整合的时间进程。结果发现随着启动音（从纯音、复合音到目标元音本身）和目标元音频谱相似度的增加,启动效应延续的时间越来越长。实验结果支持语音范畴知觉存在早期的声学特征分析和整合到后期的范畴知觉阶段,并为这些加工阶段的时间进程提供了初步的证据。     

The interdependence of pitch and temporal judgments by absolute pitch possessors

The auditory tau and the kappa effects show that there is time-pitch interdependence in our perception. Our judgments of pitch separation between two tones depend on the temporal interval between them (the auditory tau effect), and our judgments of the tones’ temporal interval depend on their pitch separation (the kappa effect). The mechanisms underlying this interdependence were investigated by studying the auditory tau and the kappa effect in three experiments. Comparisons were made between results obtained from subjects with absolute pitch and those who did not have absolute pitch, and two frequency ranges of pure tones (octave and whole-tone conditions) were selected. The procedures had been used in previous experiments (Shigeno, 1986), in which the auditory tau and the kappa effects were compared in speech and nonspeech stimuli. The present results demonstrate that the auditory tau effect does not occur when possessors of absolute pitch judge the closeness of stimuli in pitch, except when the stimulus continuum consists of tones that do not correspond to musical notes in the whole-tone condition. The kappa effect was obtained in the judgment of possessors of absolute pitch in both the octave and the whole-tone conditions. These findings suggest that the interaction between temporal interval and pitch judgment might be explained in terms of the two different memory modes for retaining the pitch of tones, and that these effects occur at the precategorical level.     

Distractor clustering enhances detection speed and accuracy during selective listening

The effects of distractor clustering on target detection were examined in two experiments in which subjects attended to binaural tone bursts of one frequency while ignoring distracting tones of two competing frequencies. The subjects pressed a button in response to occasional target tones of longer duration (Experiment 1) or increased loudness (Experiment 2). In evenly spaced conditions, attended and distractor frequencies differed by 6 and 12 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1048-Hz distractors). In clustered conditions, distractor frequencies were grouped; attended tones differed from the distractors by 6 and 7 semitones, respectively (e.g., 2096-Hz targets vs. 1482- and 1400-Hz distractors). The tones were presented in randomized sequences at fixed or random stimulus onset asynchronies (SOAs). In both experiments, clustering of the unattended frequencies improved the detectability of targets and speeded target reaction times, Similar effects were found at fixed and variable SO As. Results from the analysis of stimulus sequence suggest that clustering improved performance primarily by reducing the interference caused by distractors that immediately preceded the target.