Experimental comparison of brightness judgments obtained by rating and bisection methods

The consistency of psychophysical scales obtained by different measurement procedures is an important topic for research. Two experiments tested wheth er the scales obtained by the raring and bisection methods a ere consistent . 40 university students bisected intervals on the brightness continuum and subsequently rated the brightnesses determined bi such bisections, or they first rated brightnesses and then bisected brightness intervals. Analysis shows the scales obtained by these methods were mutually consistent when a large number of response categories (the integers from 0 to 100) were used for ratings. When a small number of response categories (the integers front 0 to 6) were used, the methods were consistent only when ratings were prod uced after the bisections. This suggests that bisections may have in crease d the consistency of the rating scale by generating an internal representat ion of equally spaced sensory magnitudes subsequently used for ratings.