Anchoring and Adjustment: Self-Generated Anchors and Head Movements

Results and Discussion

Two preconditions had to be met for an adequate test of our hypotheses about self-generated anchors. First, participants had to know the self-generated anchor. Second, they had to report considering the anchor when making their estimate. Participants who did not meet these preconditions were excluded on an item-by-item basis. On three questions, fewer than 30% of participants met both preconditions, generally because they did not know the intended anchor value. In some cases this left no participants in one or more of the experimental conditions. We therefore dropped from the analyses three questions (about the fastest mile, death of the first apostle, and orbit of Io). This left nine self-generated anchoring questions (three in the first block, four in the second, and two in the third).

To determine whether head movements influenced participants’ responses, answers to each question were converted to standard scores and then averaged across all items within each block (i.e., within each head movement condition). Reaction times were logarithmically transformed to reduce skew, then standardized and averaged in the same fashion. Answers to the four items that required downward adjustment were reverse scored so that, like the other questions, higher scores on this index reflected a larger discrepancy between the anchor and final answer. As can be seen in Table 7.2, a repeated measures ANOVA on this composite measure indicated that participants’ head movements significantly influenced their answers to the self-generated anchoring items, F (2, 84) = 3.89, p < .05. A follow-up contrast showed that participants provided answers closer to the self-generated anchor (i.e., they adjusted less) when they were nodding their heads than when they were shaking their heads, F (1, 42) = 6.44, p < .05. Participants gave responses in between those in these two conditions when they were holding their heads still. Responses to individual items, in raw scores, are presented in Table 7.3.

Table 7.2. Mean Standardized Answers and Reaction Times to the Self-Generated and Experimenter-Provided Anchoring Items Given While Participants Were Nodding, Shaking, or Holding Their Heads Still (Study 2)

Table 7.2 is not included in the supplied excerpt.

Table 7.3. Mean Responses to Self-Generated Anchoring Items Given While Participants Were Nodding, Shaking, or Holding Their Heads Still (Study 2)

Table 7.3 is not included in the supplied excerpt.

a The data presented for this item are adjustment scores, or the absolute difference between the participant’s answer and their reported anchor. This was done because adjustment was common in both directions from the self-generated anchor on this item. Lower numbers indicate a smaller discrepancy between the final answer and the original anchor (i.e., less adjustment).

Participants’ head movements also influenced the speed with which they generated their answers to the self-generated anchoring items, F (2, 84) = 5.67, p < .05. As predicted, participants answered more quickly when nodding than when shaking their heads, F (1, 42) = 11.76, p < .01. Again, the latency of participants’ responses fell in between those in these two conditions when they were holding their heads still.

We contend that participants adjust in a serial fashion from self-generated anchors and that head movements influenced their responses by altering their willingness to accept values that came initially to mind. Participants were more willing to accept values that initially came to mind while nodding their heads, producing less adjustment and faster reaction times than when they were shaking them. This mechanism differs considerably from the selective accessibility model that appears to explain anchoring effects in response to experimenter-provided anchors, suggesting that different psychological processes may be operating in these two contexts. Consistent with this contention, Table 7.2 shows that participants’ head movements did not have the same influence on responses to the experimenter-provided anchoring items.