Capturing Skill State in Curriculum Learning for Human Skill Acquisition

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Hedging your bets: intermediate movements as optimal behavior in the context of an incomplete decision.

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

Data from: Hedging your bets: intermediate movements as optimal behavior in the context of an incomplete decision

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

Expt2_Data

Matlab .mat file containing data from Experiment 2

Time-dependent competition between goal-directed and habitual response preparation.

Habits are commonly conceptualized as learned associations whereby a stimulus triggers an associated response. We propose that habits may be better understood as a process whereby a stimulus triggers only the preparation of a response, without necessarily triggering its initiation. Critically, this would allow a habit to exist without ever being overtly expressed, if the prepared habitual response is replaced by a goal-directed alternative before it can be initiated. Consistent with this hypothesis, we show that limiting the time available for response preparation can unmask latent habits. Participants practiced a visuomotor association for 4 days, after which the association was remapped. Participants easily learned the new association but habitually expressed the original association when forced to respond rapidly (~300-600 ms). More extensive practice reduced the latency at which habitual responses were prepared, in turn increasing the likelihood of their being expressed. The time-course of habit expression was captured by a computational model in which habitual responses are automatically prepared at short latency but subsequently replaced by goal-directed responses. Our results illustrate robust habit formation in humans and show that practice affects habitual behaviour in two distinct ways: by promoting habit formation and by modulating the likelihood of habit expression

Expt1_Data

Matlab .mat file containing data from Experiment 1