A Circle-Drawing Task for Studying Reward-Based Motor Learning in Children and Adults

Abstract

Childhood is an obvious period for motor learning, since children's musculoskeletal and nervous systems are still in development. Adults adapt movements based on reward feedback about success and failure, but it is less established whether school-age children also exhibit such reward-based motor learning. We designed a new 'circle-drawing' task suitable for assessing reward-based motor learning in both children (7-17 years old) and adults (18-65 years old). Participants drew circles with their unseen hand on a tablet. They received binary reward feedback after each attempt based on the proximity of the average radius of their drawing to a target radius set as double the radius of their baseline drawings. We rewarded about 50% of the trials based on a performance-dependent reward criterion. Both children (10.1 ± 2.5 (mean ± SD) years old) and adults (37.6 ± 10.2 years old) increased the radius of their drawings in the direction of the target radius. We observed no difference in learning between children and adults. Moreover, both groups changed the radius, less following reward than following reward absence, which is a sign of reward-based motor learning. We conclude that school-age children, like adults, exhibit reward-based motor learning.

Keywords: adaptation; development; motor learning; reward.

Figure A1

Spatial resampling for radius calculation.

Figure A2

Motivation scores for children and adults. A score of one indicates low motivation, a score of five high motivation.

Figure A3

Learning for children and adults instructed in Dutch or English.

Figure A4

Task-irrelevant trial-to-trial changes. (a) Changes in circularity, as quantified by the aspect ratio. (b) Changes in position on the drawing tablet, as quantified by the Euclidean distance between subsequent circle center positions.

Figure 1

Experimental task. (a) Participants were presented with a picture of a noseless bear on a laptop monitor. Their instruction was to give the bear a nose by drawing a circle of a correct size on a drawing tablet next to the laptop. Circles were drawn without visual feedback of the hand and drawing trajectory. After each trial, binary reward feedback was provided by means of a happy or sad bear face and a bell or buzzer sound. (b) Histogram of the ages in our study population. (c) Examples of circles drawn by one of the children and one of the adults. The first and the last five attempts are shown, as well as a circle with the individual baseline radius (dashed circle) and one with the target radius (solid circle), which was set to twice the baseline radius. (d) Trials were adaptively rewarded if errors were smaller than the fifth-sized error of the past ten trials. This was done to keep the reward frequency close to 50%.

Figure 2

Learning and variability during the task. (a) Fraction learned over trials. Plotted are the median and interquartile range over the participants. (b) Final fraction learned per age group. (c) Variability following rewarded (signaling success) and non-rewarded (signaling failure) trials, expressed as the median trial-to-trial ratio in the radii. (d) Final fraction learned as a function of age. Note that age has been plotted on a logarithmic scale. For visualization purposes, we computed smoothed curves of the development of learning as a function of log-transformed age by calculating weighted averages using a moving Gaussian with a standard deviation of log(1.1) for defining weights of data points centered around each log-transformed year of age [33]). (e) Variability following success (in grayscale print: lighter gray) and following failure (in grayscale print: darker gray) as a function of age. Same method as panel (d). In all panels, dots indicate individual participants.