1. Relationship of Working Memory to the Effect of Listener Training on Pitch and Rhythm Perception Sandra J. Guzman 1, Julian Milone 1, Kenneth Meinke 1, Valeriy Shafiro 2 & Stanley Sheft 2 1 Audio Arts & Acoustics, Columbia College, Chicago IL; 2 Communication Disorders & Sciences, Rush University, Chicago IL Introduction Experience and training can affect auditory performance, with a general finding that experience interacts with task complexity. Complexity often involves processing of multidimensional stimuli. The current work examined how experience affected processing of tonal sequences defined by both pitch contour and sequence rhythm. To vary the extent of musical training, subjects were recruited from both music and audio-arts academic programs. Results from our past work suggested that the relationship between pitch and rhythm processing may be affected by working memory (Guzman et al., 2015). The current work directly assessed the association of working memory to performance in the tonal- sequence task. Method Subjects: 23 normal-hearing individuals (age: 18-29); 7 were from the Audio Arts program at Columbia College and 16 were music majors. Both programs include auditory training in their curriculum. For Audio Arts (involving sound design and production), training is in both subjective (e.g., sound quality) and objective (e.g., loudness and distortion) critical listening. Music majors are trained in aural skills focusing on melodic dictation, and interval and chord identification. Along with academic program, level of musical training was quantified by number of years of instrumental or vocal practice and current hours per week of practice (Table 1). Three subjects from each group (audio arts & music major) played a rhythm instrument (drums or bass guitar) as a primary or secondary instrument. Tonal Sequence-Reconstruction Task: with four-tone frequency patterns, the listening task was to re-assemble the constituent tones in the order of a target sequence (Fig. 1). To increase memory demands, sequence tones were assigned a random response button on each trial. Subjects heard the target sequence only once, but could listen to both constituent tones and their interim reconstruction of the sequence as often as wanted. Correct-answer feedback for each sequence tone was provided after every trial. In each condition, data were collected from a single 25-trial block which was preceded by four practice trials. Stimulus level was 75 dB SPL. Conditions were repeated over three separate sessions separated by roughly one week. Conditions: Identical Target and Response Sequences Pitch Only: fixed tone duration (212 ms) with frequency randomly selected from a logarithmically scaled distribution (400-1750 Hz). Rhythm Only: fixed tone frequency (837 Hz) with a randomly selected log scaled duration (75-600 ms). Pitch & Rhythm: random frequency and duration. Dissimilar Target and Response Sequences Pitch – Rhythm: both frequency and duration were randomized with only frequency defining the target sequence so that the task was reconstructing a pitch contour using a random rhythmic sequence. Rhythm - Pitch: both frequency and duration were randomized with only rhythm defining the target sequence (i.e., rhythm reconstruction with a random pitch sequence). A minimum frequency-separation factor of 1.2 and duration-separation factor of 1.4 was assured between any two sequence tones. Letter-Number Sequencing (LNS) Task: as a test of working memory, subjects separated and arranged in ascending and alphabetical order randomly presented strings of letters and numbers of increasing length. Fig. 1. Illustration of the tonal sequence-reconstruction task. The sequence tones represented by the four boxes labeled A, B, C and D are rearranged in the upper place holders to reconstruct the original or target pattern. Results LNS scores (Table 1) were not significantly different between the two groups defined by Music Degree, and did not show significant correlation to either number of practice years or hours of current musical practice. A relatively wide performance range was obtained across subjects in the tonal sequence-reconstruction task, with a trend for an effect of Repetition most apparent in the Pitch Only and Pitch & Rhythm conditions (Fig. 2). Data analysis evaluated performance in terms of the proportion of tonal sequence components correctly placed per trial, with a logit transform of the metric (Fig. 3). A mixed-effects linear model was used with Subject and Condition nested within Repetition as random factors. Analysis showed significant main effects of Music Degree, Repetition, and Condition, along with significant interactions between Condition and either Music Degree or LNS score (Table 2). The two metrics of musical practice from Table 1 were not significant when added to the model, either with and without inclusion of Music Degree as a factor. Post-hoc analysis indicated that the effect of Music Degree was due to better performance in conditions in which pitch cued sequence reconstruction (Pitch Only, Pitch & Rhythm, Pitch - Rhythm). Correlation analysis suggested that the interaction of LNS and Condition was due to involvement of working memory in conditions in which rhythm was the only cue (Rhythm Only, Rhythm - Pitch). With variation of both pitch and rhythm, there was a significant benefit of combining the cues (Pitch & Rhythm) without evidence of interference (Pitch - Rhythm Only, Rhythm – Pitch), and with no effect of Music Degree, LNS, or Repetition on the performance deltas. Response times decreased with Repetition (Fig. 4), with a significant effect of Music Degree leading to shorter times when pitch cued sequence reconstruction. Discussion & Summary Carey et al. (2015) reported no difference between professional musicians and non-musicians on a task requiring reconstruction of isochronous sequences of tones from a C major chord. Current tonal- sequence results did show an effect of musicianship, if defined as pursuing a music degree rather than through counting metrics based on time spent on music practice. The effect of Music Degree was obtained when pitch, and not rhythm, cued tonal sequence reconstruction. It is not known how level of musical proficiency might alter these findings in other subject cohorts. Working memory, as assessed by the LNS procedure, did not show significant association with any metric of musicianship. However, LNS scores did significantly interact with Condition in the tonal sequence- reconstruction task. In contrast to the effect of Music Degree, involvement of LNS was in tonal-sequence conditions cued by rhythm only, and not by pitch. An effect of working memory in a musical task independent of musicianship is consistent with recent results of Smayda et al. (2015). Shorter response times in the tonal-sequence task potentially could reduce the demands on working memory. Despite generally shorter response times in Conditions/Repetitions with better tonal-sequence performance, LNS scores showed no relationship to the effect. There was an asymmetric interaction between the dimensions of pitch contour and rhythm in the sequence-reconstruction task. Results showed a significant benefit of combining the two dimensions without evidence of interference when only one dimension was informative. Consistent with past work (Palmer & Krumhansl, 1987; Thompson, 1994), results thus indicate variation in the manner in which dimensional information is combined in the processing of tonal sequences. Table 1. Characteristics and mean Letter-Number Sequencing (LNS) score for the two subject groups. Numbers in parentheses are S.D. or min & max values. AgeLNS Score Practice (yrs) Current Practice (hrs/week) Audio Arts (n = 7) 21 (1.3)11.9 (3.2)10.4 (3-17) 9.4 (0-38) Music Degree (n = 16) 21.6 (3.3)12.1 (2.2)13.8 (5-22) 19.6 (0-48) Fig. 2. Box plots showing results from all subjects in the tonal sequence-reconstruction task. The dependent variable is the proportion of sequences correctly reconstructed. Chance performance is.04. Fig. 3. Mean group performance in terms of the transformed proportion of components correctly placed per trial. Error bars represent the 95% confidence intervals. Chance performance is -1.1. Fig. 4. Mean group response times in the tonal sequence-reconstruction task. Error bars represent the 95% confidence intervals. Table 2. Linear mixed-effects modeling of performance in the tonal sequence- reconstruction task. 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