Do synergies improve accuracy? A study of speed-accuracy trade-offs during finger force production

Stacey L. Gorniak, Marcos Duarte, Mark L. Latash

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

We explored possible effects of negative covariation among finger forces in multifinger accurate force production tasks on the classical Fitts's speed-accuracy trade-off. Healthy subjects performed cyclic force changes between pairs of targets "as quickly and accurately as possible." Tasks with two force amplitudes and six ratios of force amplitude to target size were performed by each of the four fingers of the right hand and four finger combinations. There was a close to linear relation between movement time and the log-transformed ratio of target amplitude to target size across all finger combinations. There was a close to linear relation between standard deviation of force amplitude and movement time. There were no differences between the performance of either of the two "radial" fingers (index and middle) and the multifinger tasks. The "ulnar" fingers (little and ring) showed higher indices of variability and longer movement times as compared with both "radial" fingers and multifinger combinations. We conclude that potential effects of the negative covariation and also of the task-sharing across a set of fingers are counterbalanced by an increase in individual finger force variability in multifinger tasks as compared with single-finger tasks. The results speak in favor of a feed-forward model of multifinger synergies. They corroborate a hypothesis that multifinger synergies are created not to improve overall accuracy, but to allow the system larger flexibility, for example to deal with unexpected perturbations and concomitant tasks.

Original languageEnglish (US)
Pages (from-to)151-172
Number of pages22
JournalMotor control
Volume12
Issue number2
DOIs
StatePublished - Apr 2008

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All Science Journal Classification (ASJC) codes

  • Physical Therapy, Sports Therapy and Rehabilitation
  • Clinical Neurology
  • Physiology (medical)

Cite this

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abstract = "We explored possible effects of negative covariation among finger forces in multifinger accurate force production tasks on the classical Fitts's speed-accuracy trade-off. Healthy subjects performed cyclic force changes between pairs of targets {"}as quickly and accurately as possible.{"} Tasks with two force amplitudes and six ratios of force amplitude to target size were performed by each of the four fingers of the right hand and four finger combinations. There was a close to linear relation between movement time and the log-transformed ratio of target amplitude to target size across all finger combinations. There was a close to linear relation between standard deviation of force amplitude and movement time. There were no differences between the performance of either of the two {"}radial{"} fingers (index and middle) and the multifinger tasks. The {"}ulnar{"} fingers (little and ring) showed higher indices of variability and longer movement times as compared with both {"}radial{"} fingers and multifinger combinations. We conclude that potential effects of the negative covariation and also of the task-sharing across a set of fingers are counterbalanced by an increase in individual finger force variability in multifinger tasks as compared with single-finger tasks. The results speak in favor of a feed-forward model of multifinger synergies. They corroborate a hypothesis that multifinger synergies are created not to improve overall accuracy, but to allow the system larger flexibility, for example to deal with unexpected perturbations and concomitant tasks.",
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Do synergies improve accuracy? A study of speed-accuracy trade-offs during finger force production. / Gorniak, Stacey L.; Duarte, Marcos; Latash, Mark L.

In: Motor control, Vol. 12, No. 2, 04.2008, p. 151-172.

Research output: Contribution to journalArticle

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