Figure 1. Partial schematic of the paradigm design and examples of stimuli and associated parametric terms.

A partial schematic of the paradigm is depicted in the upper portion of the figure, and example stimuli are shown in the lower portion of the figure. Participants were given a verbal cue 1.2 seconds prior to stimulus onset as to which stimulus attribute to count (color, shape, size), and this cue remained on the screen throughout the entire trial. Participants then had 4 seconds to respond with the appropriate button press (1,2,3). ISI stands in for the variable interstimulus interval. Each stimulus was assigned an integer value (1,2,3) based on the number of dimensions, corresponding to its complexity. Stimulus A was assigned a stimulus complexity value of 1, since it did not differ on any dimensions. Stimuli B and C each contained two dimensions (B: size and shape; C: shape and color) and were assigned a stimulus complexity value of 2. Stimulus D had three dimensions (shape, size, color) and was assigned a stimulus complexity value of 3. To determine the response complexity, the number of potential valid responses were counted for each stimuli, not assuming a specific cue. For stimulus A, there was only one potential response option, as there was only one color, one shape, and one size presented. The only valid button press was 1, and stimulus A was assigned a response complexity value of 1. For stimulus B, there were two potential response options, as there was one color, two sizes, and two shapes. Valid button presses were 1 and 2, and stimulus B was, thus, assigned a response complexity value of 2. For stimulus C, there were three potential response options: one size, two colors, and three shapes (valid button presses were 1, 2, and 3). A response complexity value of 3 was assigned to stimulus 3. Finally, for stimulus D, there was again only one potential response option, as there were three sizes, three shapes, and three colors (valid button press was 3).