Análise psicofísica de medidas subjetivas de tempo em contexto rítmico / Psychophysical analysis of subjective measures of time in rhythmic context

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Purpose: To study mechanisms that limit the accuracy of rhythm production and sensorimotor synchronization analyzing the variability in finger tapping tasks, be they spontaneous finger tapping, sensorimotor synchronization to external metronomes, or rhythm maintenance after turning off the external metronome. Methods: A total of 11 participants (mean age ± 23 years, 5 men, right handed and musically untrained) performed finger tapping tasks, with the constraint of highest possible regularity, in 3 experiments: spontaneous tapping, tapping in synchrony to external metronomes (light flashes or sound bips) with periods of 200 ms, 400 ms and 800 ms, and maintaining a steady pace set by the external metronome, after it was turned off. Data analysis focused on analysis of standard deviations and coefficients of variation. Results: The average frequency chosen by participants in spontaneous rhythm production was 527.5 ms with a standard deviation of 107 ms, corresponding to a frequency around 2 Hz. Average individual standard deviation was approximately 29 ms. Synchronization (and continuity) to the light metronome was significantly more imprecise and variable than synchronization to the sound metronome (p = 0.005). This difference persisted even in the continuation tasks, for both sound and light metronomes. Surprisingly, the stability in the continuation task was significantly better than during synchronization (p <0.004). Another important result was that the coefficient of variation (ratio of standard deviation to mean period; approximately 5%) was more stable than the standard deviation in all experimental conditions. Discussion: Data from this study confirm the literature, suggesting that the spontaneous frequency of periodic movements of humans is around 2 Hz, which reinforces the idea that they are based on anatomical substrates (biomechanical resonances), which are relatively invariant across individuals. Data from this study also confirmed literature reports that timing to sound metronomes is significantly more accurate and less variable than timing to light metronomes The greater stability in the continuation task than in synchronization task suggests that external cues interfere with the internal clock. The stability of the coefficient of variation, higher than the stability of the standard deviation suggests that the internal clock is based on accumulation mechanisms. Conclusion: The frequency of 2 Hz in the rhythmic oscillatory movements of humans is probably inherent to anatomical substrates that are relatively constant across individuals. Sound metronomes are more efficient in guiding finger tapping tasks than light metronomes. It was not possible to separate out the contribution of the internal clock to the variability of finger tapping, because stability was higher the continuation phase than in the synchronization phase, both with sound and with light metronomes. Finally, the stability of the coefficient of variation suggest the direct involvement of accumulation mechanisms in the internal clock, at least on the time scales of these experiments (200 to 800 ms).

ASSUNTO(S)

musical cognition ritmo time perception attention cognição musical rythm atenção percepção de tempo

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