Aug 9, 2015 - Samuel Sparks. Ada Kritikos. Motor Priming ... attention (Bargh, 1992; Cohen, Dunbar, & McClelland, 1992). Selective Attention. (Chong et al.
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Kinematics of observed actions prime subcomponents of motor output under attentional load
Samuel Sparks Ada Kritikos
Motor Priming Seeing a human model’s action affects the observer’s motor output.
(Brass, Bekkering, Wohlschlager, & Prinz, 2000; Heyes, 2011; Kilner, Paulignan & Blakemore, 2003)
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Motor Priming (Chong et al., 2009)
Motor Priming (Chong et al., 2009)
Observe
Execute
Initiation Time
Compatible
Faster 410 ms
Incompatible
Slower 434 ms
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Ideomotor Theory Perceived and planned actions are represented by the same mechanism. Just as planning an action activates the motor code required to execute it, so does observing an action.
(Hommel, Müsseler, Aschersleben, & Prinz, 2001; Prinz, 1997; Shin, Proctor, & Capaldi, 2010)
Research Question
Does motor priming depend upon attention?
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Automatic Motor Priming? Task-irrelevant actions induce motor priming, even when priming interferes with the task. Hence, motor priming may be automatic, and is often labelled as ‘automatic imitation’ (Heyes, 2011). Automatic processes operate without requiring attention (Bargh, 1992; Cohen, Dunbar, & McClelland, 1992).
Selective Attention (Chong et al., 2009) Grasp type go signal: Priming as usual.
Diamond colour go signal: No priming.
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Attentional Modulation
Still images vs. full-motion actions
Load Theory Lavie (1995, 2010)
Limited pool of attentional resources. – Any free attentional resources ‘spill over’ to taskirrelevant stimuli. – Under high perceptual load, attentional capacity is exhausted so can longer spill over.
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Perceptual Load Evidence that task-irrelevant motion not processed under high perceptual load (Cosman & Vecera, 2010; Rees et al., 1997)
Attentional constraint of motor priming?
Priming of trajectory kinematics in reach-to-grasp actions (Hardwick & Edwards , 2011).
‘Exaggerated’ Reach
‘Straight’ Reach
Target
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Apparatus
Start
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Go Trial
No-go Trial
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Straight
Exaggerated
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Perceptual Load Manipulation Perceptual load group (n = 15) – visual detection task during action observation.
No load control group (n = 14) – no detection task.
Attentional Load Manipulation
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Colour Change (83 ms)
Motion Capture Recording Used ProReflex (Qualisys) motion capture infrared camera system to record the coordinates of passive reflective markers in 3-dimensional space during participants’ reaches.
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Results - Kinematics Kinematic parameters analysed with 2 x 2 Mixed ANOVAs Observed reach (Within-Ps): Straight vs. Exaggerated Attentional Condition (Between-Ps): No Load vs. Perceptual Load
Z Deviation
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Z Deviation 35 30 25
Observed Reach
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Z Deviation 15 (mm) 10
Straight
Exaggerated
5 0 No Load
Perceptual Load
Attention Condition
Timing Parameters Several timing parameters modulated by perceptual load, but not observed trajectory. Time to grasp – took longer to grip target. Time to Peak Radial Velocity – took longer to reach peak velocity. Time to peak grasp – took longer to prepare grasp
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Time to Peak Radial Velocity 340 320
Time (ms)
Observed Reach Straight
300 280
Exaggerated
260 240 No Load
Perceptual Load Attention Condition
Discussion Motor priming of observed reach trajectory was not attenuated when attentional resources were drawn away from the action. • Consistent with automaticity of motor priming (Heyes, 2011). • In terms of ideomotor theory, the same mechanism that represents planned actions may automatically encode observed actions.
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Discussion Increased perceptual load during observation interfered with timing parameters of subsequent reaches. • Could reflect disruption of motor preparation due to attention load. • Or disruption of priming – but unlikely because of no interaction with observed trajectory.
Discussion Contrasts with previous studies that abolished motor priming by drawing attention away from actions (Bach et al., 2007; Chong et al., 2009). • Stimuli - Full-motion actions vs. still snapshots. • Measures: Kinematics vs. initiation time
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Questions?
Thanks to: Emma & Amy (models) Merryn Constable Perception and Action Lab
Results – Task Performance Overall – performance good but not perfect, so the task was challenging and attention was engaged. Detection task • Most participants (80%) detected all targets • Few participants (13%) made false alarm errors Go/No-Go Task • No more than 3 errors per participant, most made none. • No difference in error rate according to attentional load condition.
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