Observers perceive the vertical rod tilted in the same direction as the outer frame.
Only the illusory tilt of the inner frame, induced by the outer frame, influences the perceived orientation of the rod. In previous studies with DFDs, we used a forced-choice procedure, which commonly produces results equivalent to the adjustment method. Here we report a difference between the two methods. The adjustment procedure fails to produce the HO effect. We hypothesise that this result is due to the DFD not being perceived as a single object.