Titchener's ⊥ with its lines tilted-A partial replication and extension of Cormack and Cormack (1974)

Following Cormack and Cormack (Perception & Psychophysics, 16, 208-212, 1974), modified versions of Titchener's (Experimental Psychology, Vol. 1, Pt. 1, 1901) ⊥, in which the ⊥'s lines were tilted (Experiment 1), or tilted and dissected into two separate lines (Experiment 2), were used as stimuli. In Experiment 1, the overestimation of the length of the ⊥'s vertical, undivided line tended to decrease with its tilt relative to the horizontal, divided line. For ⊥s rotated 90° or 270°, the divided line was tilted, and the overestimation of the length of the now horizontal, undivided line vanished except for ⊥s with orthogonal lines. Separation of the ⊥'s lines in Experiment 2 led to an attenuation of the overestimation of the length of the undivided line for the default ⊥, and an underestimation of the length of this line for rotated ⊥s. Results only partly confirm Cormack and Cormack, probably because of the different psychophysical methods used. Findings support the notion of a T-schema as a coherent unit in midlevel visual processing, but also suggest medium- and long-range interactions between orientation-sensitive neural mechanisms.