Figure 3. Discrimination experiment: stimuli and trials.

Representation of the five object levels used in the discrimination experiment. Each level consisted of two trials (one “same” and one “different” trial). The first row shows the objects used for the trials of object level 1. Stimulus 25 was shown twice in the “same” trial while the adjacent objects (13 and 38) were shown in the “different” trial. Rows 2 to 5 show the objects used for in the object levels 2 to 5 respectively. In all levels, the object with the number in black was used twice in the “same” trials, while the objects labeled in grey were used in the “different” trials. Note that for object level 3, the objects of the “different” trial straddle the physical category boundary.