Experimental design. (A) Example hierarchy and hidden relational rank-order structure. Participants were presented with randomly generated hierarchies from a stimulus set that involved either faces, scenes, or objects. Adjacent premise pairs (e.g., A?B) were used during training, and nonadjacent inference pairs were used during a delayed test to assess relational learning. (B) Example training trials. Participants are asked on each trial to select the item hiding a smiley face and were given feedback after each selection. (C) Stimulus pairs can be represented along two orthogonal feature dimensions: symbolic distance (the difference in rank), which is represented on the X-axis, and joint rank (the sum of the ranks), which is represented on the Y-axis.
