title: Hedging your bets: intermediate movements as optimal behavior in the context of an incomplete decision.
abstract: Existing theories of movement planning suggest that it takes time to select and prepare the actions required to achieve a given goal. These theories often appeal to circumstances where planning apparently goes awry. For instance, if reaction times are forced to be very low, movement trajectories are often directed between two potential targets. These intermediate movements are generally interpreted as errors of movement planning, arising either from planning being incomplete or from parallel movement plans interfering with one another. Here we present an alternative view: that intermediate movements reflect uncertainty about movement goals. We show how intermediate movements are predicted by an optimal feedback control model that incorporates an ongoing decision about movement goals. According to this view, intermediate movements reflect an exploitation of compatibility between goals. Consequently, reducing the compatibility between goals should reduce the incidence of intermediate movements. In human subjects, we varied the compatibility between potential movement goals in two distinct ways: by varying the spatial separation between targets and by introducing a virtual barrier constraining trajectories to the target and penalizing intermediate movements. In both cases we found that decreasing goal compatibility led to a decreasing incidence of intermediate movements. Our results and theory suggest a more integrated view of decision-making and movement planning in which the primary bottleneck to generating a movement is deciding upon task goals. Determining how to move to achieve a given goal is rapid and automatic.
authors.affiliation: Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Haith
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: David M
authors.initials: DM
authors.lastname: Huberdeau
authors.affiliation: Department of Neurology, Johns Hopkins University, Baltimore, Maryland, United States of America; Department of Neuroscience, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: John W
authors.initials: JW
authors.lastname: Krakauer
mesh_terms: D000293:Adolescent; D000328:Adult; D003657:Decision Making / Q000502:physiology*; D005260:Female; D006040:Goals; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D035501:Uncertainty; D055815:Young Adult
references.citation: Neural Comput. 2008 Apr;20(4):873-922
references.pmid: 18085991
references.citation: J Neurosci. 2006 Apr 5;26(14):3697-712
references.pmid: 16597724
references.citation: Exp Brain Res. 1983;51(2):247-60
references.pmid: 6617794
references.citation: Front Neuroeng. 2012 Apr 04;5:5
references.pmid: 22493577
references.citation: J Neurophysiol. 1997 Aug;78(2):1108-19
references.pmid: 9307138
references.citation: Nat Neurosci. 2002 Nov;5(11):1226-35
references.pmid: 12404008
references.citation: Exp Brain Res. 2011 Dec;215(3-4):235-45
references.pmid: 21997330
references.citation: Curr Opin Neurobiol. 2012 Dec;22(6):927-36
references.pmid: 22683275
references.citation: Nat Neurosci. 2010 Mar;13(3):379-85
references.pmid: 20098418
references.citation: J Neurosci. 2013 Oct 9;33(41):16394-408
references.pmid: 24107969
references.citation: Neuron. 2010 Nov 4;68(3):387-400
references.pmid: 21040842
references.citation: Neuron. 2005 Mar 3;45(5):801-14
references.pmid: 15748854
references.citation: J Neurosci. 2011 Jun 8;31(23):8406-21
references.pmid: 21653845
references.citation: Neuron. 2011 May 12;70(3):536-48
references.pmid: 21555078
references.citation: J Exp Psychol Gen. 1980 Dec;109(4):444-74
references.pmid: 6449531
references.citation: PLoS Comput Biol. 2012;8(11):e1002774
references.pmid: 23166483
references.citation: Vision Res. 1999;39(25):4200-16
references.pmid: 10755158
references.citation: J Neurosci. 2008 Oct 29;28(44):11360-8
references.pmid: 18971478
references.citation: J Neurophysiol. 1996 Dec;76(6):4040-55
references.pmid: 8985899
references.citation: J Neurophysiol. 2013 Aug;110(4):807-16
references.pmid: 23699052
references.citation: Nature. 2012 Jul 5;487(7405):51-6
references.pmid: 22722855
references.citation: Trends Cogn Sci. 2001 Jan 1;5(1):10-16
references.pmid: 11164731
references.citation: J Neurosci. 2006 Sep 20;26(38):9761-70
references.pmid: 16988047
references.citation: Nature. 2000 Mar 23;404(6776):390-4
references.pmid: 10746726
references.citation: J Neurosci. 2014 Jan 29;34(5):1769-80
references.pmid: 24478359
references.citation: J Neurosci. 2012 Feb 15;32(7):2276-86
references.pmid: 22396403
references.citation: Exp Brain Res. 1997 Jun;115(2):217-33
references.pmid: 9224851
references.citation: Proc Natl Acad Sci U S A. 2009 Jul 14;106(28):11478-83
references.pmid: 19574462
references.citation: J Neurophysiol. 2007 Jun;97(6):4203-14
references.pmid: 17409174
references.citation: Acta Psychol (Amst). 1967;27:143-53
references.pmid: 6062205
references.citation: Exp Brain Res. 1988;71(2):320-8
references.pmid: 3169167
references.citation: Vision Res. 1979;19(9):967-83
references.pmid: 532123
references.citation: Exp Brain Res. 1988;71(1):116-28
references.pmid: 3416946
references.citation: J Neurophysiol. 2007 Nov;98(5):3034-46
references.pmid: 17898140
references.citation: Annu Rev Neurosci. 2007;30:535-74
references.pmid: 17600525
references.citation: Exp Brain Res. 1993;95(3):429-35
references.pmid: 8224068
references.citation: Phys Rev Lett. 2005 Nov 11;95(20):200201
references.pmid: 16384034
references.citation: Nat Neurosci. 2001 Oct;4(10):1020-5
references.pmid: 11547338
references.citation: Neuroscientist. 2015 Aug;21(4):385-98
references.pmid: 24981338
references.citation: Psychol Rev. 2002 Jul;109(3):545-72
references.pmid: 12088245
references.citation: J Neurophysiol. 1981 Oct;46(4):725-43
references.pmid: 7288461
references.citation: Exp Brain Res. 1990;79(3):530-8
references.pmid: 2340872
references.citation: Nature. 2009 Sep 10;461(7261):263-6
references.pmid: 19693010
references.citation: Cognition. 2010 Aug;116(2):168-76
references.pmid: 20471007
references.citation: J Neurosci. 2013 Jun 12;33(24):9985-97
references.pmid: 23761894
references.citation: Science. 1989 Jan 13;243(4888):234-6
references.pmid: 2911737
references.citation: Trends Cogn Sci. 2009 Aug;13(8):360-6
references.pmid: 19647475