Psychometric functions.

Each panel corresponds to a different group of 22 participants. At each relative sentence length, individual data points reflect the mean proportion of “longer” sentence-length responses separately for standard (red) and flipped (blue) text. Standard text (red) generated psychometric functions with only marginally steeper slopes than did flipped text (blue) across groups. This consistent but small “inversion effect” for the precision of sentence-length judgments held for mirror-reversed (Groups M1 and M2) and upside-down text (Groups U1 and U2) alike. The midpoint (point of subjective equality, PSE) of each psychometric function tended toward zero, indicating minimal response bias near the center of the sentence-length range.