The claim that all human populations scan visual pictures from left to right is refuted by cross-cultural eye-tracking studies, which show that visual scanning patterns and saccade directions are influenced by cultural reading habits.
The claim is a universal generalization about human visual scanning behavior. Paper [0] and Paper [8] both explicitly demonstrate that scanning and reading habits vary across cultures and writing systems (e.g., top-to-bottom or right-to-left), directly refuting the idea that all human populations universally scan from left to right.