Why might visual learning with horizontal lines not transfer to vertical lines?

Visual learning with horizontal lines often fails to transfer to vertical lines because such training is highly orientation-specific. This specificity suggests that the learning process involves changes in neural processing that tune acuity to a narrow range of orientations within the primary visual cortex, rather than relying on a generalized, high-level learning process.1

Because the brain’s early stages of visual cortical processing are specialized to respond to specific stimulus attributes, training on one orientation does not automatically improve performance on another. This phenomenon is linked to the sharpening of neuronal "tuning functions," where neurons become more sensitive to a limited range of stimuli, such as a specific orientation. Consequently, when the orientation of the stimulus changes, the previously tuned neural pathways are not engaged in the same way, preventing the transfer of the learned skill.1