Serial position, distance, and congruity effects of reference point setting in comparative judgments

This study tested the hypothesis that the serial position function in serial order memory derives from a gradient of activation strength, with the end anchor point having the highest strength and accessibility. Subjects memorized an ordered series of names and were tested on their memory of the order with a comparative judgment task. In Experiment 1, a traditional comparative judgment task was used in which they chose the one member in a pair that was either higher or lower in the ranking on the attribute dimension. The 3 typical effects from comparative judgment for serial items--the bowed serial position function, the distance effect, and the congruity effect--were obtained. In Experiment 2, subjects were instructed to choose the item either closer to or farther from the middle reference point of the series. Remarkably different forms of the 3 effects were obtained. Most notable was a deep drop in the middle of the RT function, supporting the activation gradient hypothesis but further separating the role of the reference point from that of the endpoints in the assumption of the activation strength gradient theories. The findings also generalized the concept of each of these 3 effects.