Barbara E. Acker

Evidence for auditory feature integration with spatially distributed items.

Recent auditory research using sequentially presented, spatially fixed tones has found evidence that, as in vision for simultaneous, spatially distributed objects, attention appears to be important for the integration of perceptual features that enable the identification of auditory events. The present investigation extended these findings to arrays of simultaneously presented, spatially distributed musical tones. In the primary tasks, listeners were required to search for specific cued conjunctions of values for the features of pitch and instrument timbre. In secondary tasks, listeners were required to search for a single cued value of either the pitch or the timbre feature. In the primary tasks, listeners made frequent errors in reporting the presence or absence of target conjunctions. Probability modeling, derived from the visual search literature, revealed that the error rates in the primary tasks reflected the relatively infrequent failure to correctly identify pitch or timbre features, plus the far more frequent illusory conjunction of separately presented pitch and timbre features. Estimates of illusory conjunction rate ranged from 23% to 40%. Thus, a process must exist in audition that integrates separately registered features. The implications of the results for the processing of isolated auditory features, as well as auditory events defined by conjunctions of features, are discussed.

Within-category discrimination of musical chords: Perceptual magnet or anchor?

Recent speech research has begun to evaluate the internal structure of categories. In one such study, Kuhl (1991) found that discrimination was poorer for vowel stimuli that were more representative of the category (prototype, or P, set) than it was for less representative stimuli (nonprototype, or NP, set). This finding was interpreted as indicating that a category prototype may function as a “perceptual magnet,” effectively decreasing perceptual distance, and thus discriminability, between stimuli. The present study examines the function of prototypes in a musical category—another natural, but nonspeech category. Paralleling the Kuhl study, representative (P) and less representative (NP) sets of major triad stimuli were constructed, based on equal temperament. Musically experienced subjects rated the stimuli in each set for goodness as a major triad, with the highest rated stimulus serving as a prototype standard for a subsequent discrimination task. Results from the discrimination task demonstrated better performance in the P context than in the NP context. The current nonspeech results indicate that a prototype functions as an anchor rather than a magnet. In addition to providing a natural, nonspeech standard for comparison with speech findings, the results provide some important insights into the nature of musical categories.

Perceptual integrality of major chord components.

In the present study, an accuracy, rather than a reaction time, version of the Garner paradigm was used to evaluate the integrality or separability of major chord components. Tuned (prototype, or P) and mistuned (nonprototype, or NP) sets of root position C-major triads were constructed by holding the C constant in all stimuli and varying the E and G frequencies in 2- and 4-Hz steps. The P stimuli represent small systematic mistunings in the E and G notes relative to an equal-tempered C-major chord. The NP stimuli represent an equivalent range of frequency variation, but relative to a significantly out-of-tune C-major triad. In different experimental sessions, asame-different (AX) task was used to separately evaluate discrimination performance for the E and G frequencies as a function of whether the nontarget frequency (G or E) was fixed or varied in either a correlated or an orthogonal fashion (with the C frequency always held constant). Compared with a fixed baseline condition where only the target frequency changed, both chord components exhibited a significant redundancy gain in the correlated conditions and, to varying degrees, significant interference effects in the orthogonal condition, indicating that the chord components function largely in an integral fashion. Relative to the discrimination of G, discrimination of the E frequency was less influenced by variation in the nontarget (G) frequency, showing that attention, to some degree, could be selectively allocated to the E chord component. In addition, the results were consistent with previous findings that the functional prototype for the major chord category seems to act as a perceptual anchor, rather than as a magnet, and appears to be located in the physiologically defined area of just temperament, as opposed to the more experientially defined area ofequal temperament.

Directed attention and perception of frequency changes.

What role does attention play in the perception of components within a melody? A paradigm used by Palmer and Holleran [Percept. Psychophys. 56(3), 301–312] provides a basis for addressing this question. Their study investigated different influences on the perception of pitch alterations in three‐voiced musical passages, where subjects first learned a four‐measure standard, then completed a same/different task. ‘‘Different’’ passages were constructed by altering the original standard, with a harmonically related (HR) or unrelated (HU) frequency change made in the lowest, middle, or upper voices of the musical passage. Results indicated that HR changes were less detectable than HU changes and were the least detectable in the middle voice. The current study uses the same procedures and musical materials as the Palmer and Holleran work, but provides the subjects with cues indicating which frequency region might contain the alteration (low, medium, or high). Results will be discussed in terms of the role direc...

Discrimination of musical chord components

The current study uses an accuracy version of the Garner paradigm to evaluate the nature of the roles played by the E and G frequencies in the perception of root position C major triads. Triads differed in the E and/or G frequencies, relative to an equal‐tempered triad (prototype, or P set) or an out‐of‐tune triad (nonprototype, or NP set). Thus, the P stimuli were more representative of major chords than the NP stimuli. Significant redundancy gains and interference effects were found for both frequencies in both contexts, thus demonstrating the components to be integral, as might be expected for tuning based upon intervals. The amount of redundancy gain found was dependent on the type of correlation, with the negatively correlated stimuli experiencing a greater redundancy gain than the positively correlated stimuli. Finally, better overall discrimination was found in the P context, thus replicating previous work [Acker, Pastore, and Hall, Percept. & Psychophys. (in press)] showing that a prototype functi...

The role of experience in the development of category structures

Recent speech research and music work have found empirical evidence for prototypes or exemplars. Whereas the function of a speech prototype is debatable, experiments using musically trained subjects found better discrimination around major chord prototypes than near less representative members of the category. While the specific function of prototypes is of interest, the development of prototypes is also important in elucidating perceptual processes. Developmental processes in speech and music have been studied by comparing infant and adult data. Utilizing musically naive adult subjects and musical stimuli, the current work investigates perceptual differences attributable to training and experience, but avoids problems associated with infant subjects. The ability of nonmusically trained subjects to discriminate in‐tune (prototype [P] set) and mistuned (nonprototype [NP] set) major chords was evaluated in an AX task. Unlike musicians who showed significantly better performance with the P set, the naive sub...

Effects of timbre manipulations on melody perception

The effects of timbre on melody perception were explored in three‐voice homophonic (H) and polyphonic (P) pieces. Musically trained subjects learned a 12‐note melody in isolation, then listened to H and P pieces that contained the melody in either the high, middle, or low spectral positions. Three timbre conditions were created: (1) homogeneous, where all three voices were in the same timbre; (2) enhanced, where the melody was presented in a timbre distinct from the other two voices; and (3) inconsistent, where each of the three timbres formed distinct patterns which were independent of the melody (H pieces only). In a discrimination task, subjects responded to errors only in the melody, although errors could occur in the other two voices. Several patterns of results occurred which were dependent on the type of timbre manipulation and the musical context employed. Thus the results demonstrate important aspects of how principles from music cognition (melody memory, timbre manipulations) and music theory (H...

Ability to detect changes in musical pieces is a function of musical training and musical context

The ability of musicians and nonmusicians to detect a one‐note change from a fixed three‐voiced musical piece (the standard) was evaluated. Following previous studies, which had tested only musicians, several potentially important variables were manipulated. Musical context (polyphonic or homophonic) was manipulated between subjects. Melody location (high, middle, or low voice), and thus the standard, was varied for each subject across sessions. Within a session, changes varied in harmonic relatedness (related or unrelated), and voice location (high, middle, or low). Subjects performed a same‐different task and indicated their confidence as to whether or not a change had been present. Furthermore, a signal detection analysis of the subjects’ pattern of responses was performed to directly measure sensitivity to the presence of changes. As expected, musicians were more confident in their responses and revealed a higher sensitivity to changes than nonmusicians. Interestingly, the effects of musical training ...

Compositional style, frequency height, and harmonic influences on melody perception

The ability of musically trained listeners to detect changes in a learned melody was evaluated in homophonic (H) and polyphonic (P) musical passages. Subjects first learned a 12‐note melody in isolation, then listened to three‐voice fourth species counterpoints (P context) and three‐voice harmonizations (H context) that contained the melody in either the high, middle, or low spectral positions. In a discrimination task, subjects were to respond to changes in the melody only, although changes could also occur in the other two voices. A signal detection analysis found that: (1) performance in the P context was better than the H context for the high and middle melody, but was poorer than the H context for the low melody; and (2) performance for the middle melody was the same as for the high melody location. This second result suggests that the findings of previous work [e.g., Palmer and Holleran, Percept. Psychophys. 56, 301–312 (1994); Acker and Pastore, J. Acoust. Soc. Am. 99, 2482(A) (1996)], where change...

Integrality of first inversion C‐major chord components.

Previous work [Acker and Pastore, Percept. Psychophys. (in press)] using a discrimination version of the Garner paradigm found the E and G frequencies of a root position C‐major chord to be integral, with both frequencies exhibiting significant redundancy gains in the correlated condition, but with the E exhibiting less interference in the orthogonal condition than the G. This finding raised the question of whether attention was better allocated to the E frequency specifically, or if it was a function of the middle spectral location. The current work addresses this question by evaluating discrimination of chord components in a first inversion chord, where the E is the lowest frequency component instead of the middle component. Subjects completed fixed, correlated, and orthogonal discrimination tasks for each frequency. Replicating the earlier results, both frequencies experienced significant redundancy gains in the correlated condition, and the E frequency again exhibited less interference in the orthogon...