Fig. 4: Motor properties of the exploration task did not vary with haptic numerosity.

a Hand motion during haptic exploration of spheres was recorded using a glove that captures fingers motion. The epochs of spheres exploration were extracted for each finger. For each epoch, we measured b the number of unique motions as indicated by the number of peaks in the sensor values c the total amount of motion as indicated by the standard deviation of sensor values, and d the duration of motion as indicated by the start and end of the changes in sensor values irrespective of the beginning and end positions. Box plot diagrams present these parameters averaged across fingers and grouped across haptic epochs of all participants (n = 100). We did not find any difference in these parameters as numerosity increased, in either of the two haptic stimuli conditions of equal total volume or equal individual sphere size. Indeed, Bayesian statistics provided evidence that there are no differences in these parameters as a function of numerosity. In the box-plot diagram, the central mark indicates the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme data points not considered outliers, and the outliers are plotted individually using the dot symbol.