Anchor effects using numerical estimates of simple dot patterns

Shifts due to anchor stimuli using absolute judgments have been ascribed to “semantic” and “scale modulus” changes. To test this explanation, random dot patterns of 10, 12, 14, 16 and 18 dots were exposed for 0.30 sec with anchors of 4, 13 or 32 dots preceding each of the stimuli. In the control only the series of stimuli were judged. It was found that numerical estimates of the number of dots increased with small anchor, decreased with large anchor, and were not significantly changed with anchor in the vicinity of AL. These results exactly parallel those found using methods of absolute and comparative ratings and hence cannot be ascribed to semantic shifts especially in view of the fact that independent groups of Ss served in the four anchor and control conditions. Since the anchor effects were significant but not so large that they can be ascribed to change of scale modulus this theory must also be rejected. The AL model seems to offer the simplest and most unitary explanation of these as well as many other results obtained with different types of stimuli and different methods of judging.