Motor Timing

Timing our actions is something we do thousands of times a day without thinking twice—controlling our eyes to read this text or reaching out to pick up a cup. To understand timing, however, it is first necessary to draw the distinction between the concept of time and timing. Timing is a human-made physical  means  of  measuring  the  passage  of  time (e.g.,  seconds,  minutes,  hours).  How  we  perceive time,  per  se,  is  very  different  from  how  time  is measured by a watch or clock. Although the brain has no known dedicated time receptors, we are still very  adept  at  organizing  and  guiding  our  actions in  space  and  time  (timing  our  actions).  Indeed our  survival  in  the  dynamic  world  we  all  live  in requires  that  the  timing  of  our  actions  involve some  understanding  or  perception  of  the  time remaining  before  something  happens.  Prospective information  provides  information  about  the  current  future,  that  is  where  we  are  going  and  how we  will  get  there  based  on  our  current  course  of action.  For  example,  when  one  is  driving  a  car, the  changing  patterns  of  light  picked  up  by  the driver’s eyes will inform the driver about when to start braking so as to avoid colliding with the car in  front.  This  is  an  example  of  how  prospective information available in the world we live in can be used to allow us to act ahead of time. In other words, the perceptual information available to us is important in allowing us to successfully control the  timing  of  our  interactions  with  other  moving objects  or  people  who  live  in  the  same  dynamic environment.  Before  discussing  how  to  control the timing of our actions in sporting contexts, it is necessary  to  draw  a  distinction  between  different types  of  timing  and  illustrate  how  they  relate  to different types of temporal information.

Different Types of Motor Timing

Catching  a  ball,  moving  to  a  beat,  and  hitting  a golf  ball  are  all  examples  of  actions  that  require precise  timing.  More  specifically,  the  outcome  of these actions will be determined by how well the unfolding  movements  are  controlled  with  respect to either intrinsic or extrinsic temporal information specifying how the event is unfolding. For example, when  catching  a  ball,  continuous  visual  perceptual information specifying where the ball is going and  when  it  is  going  to  get  there  is  extrinsically available in the ball’s unfolding trajectory. In this case,  the  temporal  control  of  the  movement  is called  extrinsic.  That  is  to  say  the  movement  of the  ball  that  is  external  to  the  person  determines how and when one should move to get to the right place at the right time to catch it.

Alternatively, when clapping to a beat, the perceptual information available to guide the action is intermittent.  The  beat  demarcates  when  the  clap should  take  place  but  does  not  provide  any  continuous  perceptual  information  specifying  when the next beat will sound. As with all movements, the movement needs to start before the beat sounds (prospective control), so the hands come together as the beat sounds. The intermittent acoustic information available when the beat sounds is insufficient  to  time  the  movement  of  the  hands.  In  this case,  some  other  form  of  temporal  information must be provided by the brain to allow one to get their  limb  to  the  right  place  at  the  right  time  to clap to the beat.

Finally,  when  golf  putting  or  taking  a  penalty kick in rugby or soccer, neither the beginning nor the end of the movement is specified by any form of  extrinsic  temporal  information.  Instead,  the timing of the putting movement or kicking action, which is crucial for determining the velocity of the club or foot at ball impact, must again be specified by some intrinsic neural mechanisms in the brain. In this case, the action is totally self-paced in that the player determines when to begin the action and how it should unfold. The spatial temporal dynamics of the club or leg movement largely determine the success of the action with the timing of all self paced actions being provided intrinsically.

This distinction in the different types of action timing   is   critical   when   considering   skill-based learning in sport (e.g., interceptive type actions vs. self-paced).  In  the  next  section,  a  theory  is  presented for how the temporal information (intrinsic or  extrinsic)  provides  a  solid  basis  to  guide  the timing of actions in sport.

Theories for Timing Movement

A plethora of research has studied timing mechanisms in the brain when tapping along to a beat. These  studies  have  used  the  tapping  paradigm, focusing  on  the  size  and  variability  of  temporal  errors  made  when  synchronizing  taps  with beats  and  when  continuing  to  tap  when  the  beat stimulus  is  removed.  Although  timing  theories have  emerged,  they  tend  to  be  paradigm  driven only  explaining  movement  timing  when  tapping a  finger  not  when  dancing,  catching,  or  striking a  ball.  For  instance,  when  dancing,  synchronization  of  body  and  limb  movements  is  patterned (spatially)   relative   to   the   temporal   structure imposed by the music. In other words, the timing of movements is neither temporal nor spatial but is spatiotemporal—how  the  limb  position  changes over  time.  This  poses  a  genuine  problem  in  the application  of  traditional  timing  models  to  the understanding of timing in the control or coordination of goal directed action.

Thus,  to  understand  the  concept  of  timing  in the  spatiotemporal  context  the  notion  of  time needs to be reconceptualized. Instead of considering  the  brain  representing  time  like  a  clock,  it  is more appropriate to think of time’s passage, or a time  interval,  as  being  represented  by  something that changes over time. That is, time can be considered more of an abstraction that emerges from the way things change over time, which resonates with James J. Gibson’s (1975) idea that “events are perceivable, but time is not.” It is therefore more prudent  to  consider  that  the  spatiotemporal  control of actions or timing of actions must inevitably be related to the perception of events. The theory presented here, tau-coupling theory, follows from this  and  hypothesizes  that  the  perception  of  temporal  information  (either  intrinsic  or  extrinsic) guides the timing of our movements.

Temporal Information

To  understand  how  temporal  information  can guide  the  timing  of  movement,  it  is  first  of  all important  to  describe  what  is  meant  by  information. In the physical world, the way in which a spatial gap between a ball and a target closes provides robust  temporal  information  that  can  be  used  to control  the  timing  of  an  action.  David  Lee  suggested  that  the  time-to-closure  (tau)  of  a  motion gap  (in  this  case  the  distance  between  the  ball and the target) at its current closure rate provides powerful  information  for  timing  movement.  Not only is tau simple, general, robust information, it is also prospective, offering temporal information about the time remaining until a gap is closed. The appeal  of  a  prospective  informational  variable  in the context of timing is that it allows for the preparation and initiation of an action ahead of time, something that is critical in all sporting contexts.

Although  tau  as  described  above  can  explain action  timing  in  the  extrinsic  temporal  control context  like  catching  a  ball,  it  does  not  explain how  we  can  time  our  actions  in  cases  where  the temporal  control  is  intrinsic,  as  in  self-paced actions—putting  a  golf  ball.  Here  no  continuous perceptual  temporal  information  is  available  to guide movements prospectively (e.g., kicking a stationary  ball).  This  informational  void  has  to  be, therefore, filled by some internal dynamic temporal  representation  generated  in  the  player’s  brain that helps provides a temporal framework to guide the  timing  of  their  movement.  Previous  research has  proposed  a  mathematical  model  where  this temporal  information  is  specified  in  the  brain  in a  way  that  is  similar  to  the  specification  of  temporal  information  in  the  physical  world,  namely a  changing  neural  quantity  (firing  rate  or  neural power) over time.

To  control  the  timing  of  our  actions,  the  theory proposes a simple robust solution where the way the movement changes over time (the movement  τ–τm)  is  linked  to  the  perception  of  the dynamic temporal information (the informational τ–τ-guide [τi]) generated by an event in the environment  (extrinsic)  or  the  brain  (intrinsic).  This dynamic  temporal  information  therefore  prescribes  the  temporal  course  of  the  movement  so that  the  information  and  movement  are  coupled in  such  a  way  that  τm=kτi  (where  k  a  constant represents  the  volitional  control  of  movement). This  theory  explains  parsimoniously  how  we control the timing of our movements through the principles of information movement guidance.

Improving Motor Timing

Learning  a  new  self-paced  skill,  such  as  controlling the velocity of the club head when putting a golf  ball  different  distances,  is  a  difficult  skill  to master. The velocity of the club head can be controlled  by  varying  the  amplitude  of  the  back  or forward swing, the duration of the swing, or both of  these  parameters.  In  other  words,  the  way  the action unfolds over space and time to give a particular  velocity  can  arise  from  a  mixture  of  different  space-time-action  permutations.  Being  a self-paced  action,  as  mentioned  above,  the  temporal  framework  for  this  type  of  movement  is intrinsic,  generated  within  the  brain,  and  is  not directly accessible to the learner or the trainer. One exciting new way of looking at how the timing of these  actions  can  be  improved  is  by  seeing  how some  form  of  extrinsic  temporal  information  can be  provided  that  specifies  how  the  action  should unfold over time. Recent research has shown that by  externalizing  the  temporal  framework  within which an action takes place, movement variability can  be  significantly  reduced  and  the  consistency of the timing of the action be improved. Coaches and players seeking to improve the timing of self-paced  actions  should  therefore  consider  the  use of extrinsic temporal information that could help the  player  prepare  and  execute  the  timing  of  the action in a more consistent manner. Furthermore, the role of preperformance routines, often adopted by elite players to help form the temporal envelope within  which  a  self-paced  action  unfolds,  should also be carefully considered so they include some form of extrinsic temporal information that could significantly  improve  the  outcome  of  that  action. That  is,  adopting  the  aforementioned  information–movement  coupling  approach  to  consider how  the  brain  controls  the  timing  of  an  action (intrinsic  vs.  extrinsic  information)  could  lead  to new  advances  in  coaching  techniques  and  greatly advance research and practice in the area of motor timing. Finally, for interceptive actions, the information that players use is emerging as critical for determining performance outcomes.

Recent  studies  debunk  previous  research  that suggests  that  responding  as  quickly  as  possible  is of  primary  importance.  Instead,  this  research  has shown that tuning into the right source of external information (e.g., the player’s centre of mass) that specifies an action relevant property (e.g., final running  direction)  and  acting  upon  this  information in  the  appropriate  time  frame  determines  expertise. It is acting in the right way at the right time that  defines  sports  performance  in  handball,  soccer,  and  rugby,  not  acting  as  quickly  as  possible. More research is now required to understand how coaches  can  educate  players’  attention  to  enable them to tune into the right perceptual information that can be used to guide the timing of their actions.

References:

  1. Brault, S., Bideau, B., Kulpa, R., & Craig, C. M. (2012). Detecting deception in movement: The case of the sidestep in rugby. PloS ONE, 7(6), e37494. doi: 10.1371/ journal.pone.0037494
  1. Craig, C. M., Delay, D., Grealy, M. A., & Lee, D. N. (2000). Precision golf putting: Guiding the swing. Nature, 405, 295–296.
  2. Dessing, J. C., & Craig, C. M. (2010). Bending it like Beckham: How to visually fool the goalkeeper. PloS ONE, 5(10), e13161. doi: 10.1371/journal.pone.0013161
  3. Gibson, J. J. (1975). Events are perceivable but time is not. In J. T. Fraser & N. Lawrence (Eds.), The study of time, 2. New York: Springer.
  4. Lee, D. N. (1998). Guiding movement by coupling taus. Ecological Psychology, 10, 221–250.
  5. Wing, A. M., & Kristofferson, A. B. (1973). Response delays and the timing of discrete motor responses. Perception Psychophysics, 14, 5–12.

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