Generalization of learned variability across multiple dimensions in humans

This study examined whether trained variability would generalize across dimensions of the target response. Two experiments used a computerized rectangle drawing task that required participants to click and drag a mouse cursor to create rectangles on a computer screen. In Experiment 1, one group received points when successive rectangles varied in their size, shape and location (VAR), another group were yoked to the VAR group and received points that were allocated to them using a yoking procedure (YOKE), regardless of the variability in the size, shape or location of the rectangle drawn. Variability was higher for a dimension when variability on that dimension was directly reinforced. In Experiment 2, three groups of participants received points when rectangles varied on two dimensions; each group differed in the two dimensions that required variation. Variability was again higher for the reinforced dimensions for two of the three groups. Comparison with the YOKE group showed that the variability on those dimensions where variability was not directly reinforced was affected by reinforcement for variability on the other dimensions. Specifically, the variability in Shape and Location was significantly higher when these two dimensions occurred with other dimensions where variability was reinforced (as in Experiment 2) compared to when they were not required to vary (as in the YOKE group). This suggests that, for these two groups, the reinforced variability on the other two dimensions generalized to the third dimension. Implications of this finding to our understanding of factors that promote behavioral variability are discussed.