Sequential effects in successive ratio estimation

Sequential effects are examined in four successive ratio estimation (RE) experiments. The procedure in successive RE is identical to that for magnitude estimation (ME), but the task in successive RE is to estimate the ratio of the current to the previous sensation magnitude, and not the separate magnitudes of the sensations. A positive stimulus context effect was found in successive RE for several continua, in agreement with results previously found for ME. The residual autocorrelation for successive RE was zero in many cases, but in some cases negative autocorrelation was found, which is in contrast to the positive autocorrelation that is typically found for ME and other magnitude scaling procedures. It is shown that, when the role of perceptual error is recognized, negative autocorrelation is predicted by a classical model of ratio estimation. Some aspects of response bias are also discussed.