Cite as:
Hamada J, Ehrenstein W H, Paramei G V, 2003, "Size assimilation and attention" Perception 32 ECVP Abstract Supplement

Size assimilation and attention

J Hamada, W H Ehrenstein, G V Paramei

Attentional effects on size assimilation were studied with the use of Delboeuf's concentric-circles figure. Allocation of attention was varied by alternative judgment-order instructions: starting the estimation with either the inner circle as a test or with the outer circle. Absolute and relative diameters of the circles were varied in a consecutive manner (ranging between 12 and 45 mm), and apparent size was judged by the method of magnitude estimation. Induced size depended upon the diameter ratio--maximal assimilation occurred at an inner-to-outer ratio of 0.69 (overestimation of the inner circle) and of 0.51 (underestimation of the outer circle). In addition, size assimilation varied with the absolute diameter difference of circles in a nonlinear way. Allocation of attention had a modulating effect on size induction; specifically the circle judged initially was estimated more veridically, indicating weaker assimilation. Moreover, an asymmetry of assimilation effects occurred in that the smaller (inner) circle was affected more strongly than the larger (outer) circle. The results suggest that size induction does not depend merely on stimulus variables but also on instruction-modulated allocation of attention which might itself essentially rely on differential figure - ground assignment: the attended test circle, perceptually emerging as the figure, is more resistant to the inducing context; hence its perceived size remains more veridical. Conversely, the induction of the initially attended circle appears to be stronger on the subsequently attended circle that has ground character and is thus more prone to size distortion.

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