Is separation represented in terms of position?

How do humans make judgments of separation (distance in a frontal plane)? According to the additive account of separation assessment, the separation between two points is inferred from the number of instances of a unit distance lying between the points. According to the subtractive account, the separation between two points is inferred from the difference between their positions in a localization system. In response to recent findings that are consistent with the additive account and inconsistent with the subtractive account, the present study explicitly tested the subtractive account. The study tested whether separations are represented in memory in terms of positions, as would be expected under the subtractive account. In two experiments the study found no support for this possibility. Although participants showed a bias to mis-recall the members of a set of separations in the direction of the average separation in the set, participants did not show a parallel bias in recalling the positions that defined the separations. Although participants were influenced in recalling the members of a set of separations by the range of the scale that was used to specify the separations, participants were not similarly influenced in recalling the positions that defined the separations.