This registration is a frozen, non-editable version of this project
**Hypotheses and expectations** According to the scale distortion theory of anchoring (Frederick & Mochon, 2012; Mochon & Frederick, 2013), the anchoring effect occurs because perception of the scale is distorted by a previously considered value on the same scale. In the standard anchoring paradigm, where an anchor is introduced by its comparison to the target value, the presentation of this numeric value distorts perception of the scale, which influences subsequent estimation of the target value. Consistent with the scale distortion theory of anchoring, comparison of the target value to another object (which is similar in the value of the estimated attribute to the anchor) does not influence the absolute judgment of the target value (Mochon & Frederick, 2013). Moreover, comparison of the anchor with a different object than the target influences the estimate of the target value similarly as if the target object is compared to the anchor directly (Frederick & Mochon, 2012; Mochon & Frederick, 2013). This shows that the effect of the anchor has to occur during the estimate of the anchor value, because the target is not known at the time of the comparison in this experimental set-up. The present study will use this observation to test a prediction of the scale distortion theory of anchoring. If anchoring occurs at the point of the absolute judgment, the scale has to be distorted at this point for the anchoring effect to occur. The absolute judgment question has to be preceded by the comparison question for this assumption to hold. In the present experiment, several other comparisons on the same scale will be inserted between the absolute judgment question and the comparison question pertaining to the same target. According to the scale distortion theory of anchoring, the scale should not be distorted at the point of the absolute judgment in this experimental set-up and there should be no effect of the anchor. An alternative account of anchoring - the selective accessibility model (Strack et al., 2016) argues that the comparison question makes information consistent with the anchor more accessible and this information influences the answer to the absolute judgment question. The selective accessibility model is therefore consistent with the anchoring effect even when there are multiple other anchors on the same scale between the comparison question and the absolute judgment question pertaining to the same target. The information activated at the point of the comparison question will be still more accessible when the absolute judgment question is asked. Frederick, S. W., & Mochon, D. (2012). A scale distortion theory of anchoring. Journal of Experimental Psychology: General, 141(1), 124–133. Mochon, D., & Frederick, S. (2013). Anchoring in sequential judgments. Organizational Behavior and Human Decision Processes, 122(1), 69–79. Strack, F., Bahník, Š., & Mussweiler, T. (2016). Anchoring: accessibility as a cause of judgmental assimilation. Current Opinion in Psychology, 12, 67–70. **Methods** *Participants* Participants will be recruited from a laboratory subject pool to participate in a batch of studies, one of which will be the present study. The planned sample size is 500, but the final sample size might slightly differ because participants are invited some time in advance and the experiment is administered in groups of up to 17. *Materials* The study consists of two parts. In the first part of the study, participants will be given 13 objects that they will compare with a random anchor. For each item, they will first generate a random number by pressing a button and then answer whether a given object is smaller or bigger in terms of size than the generated random number by pressing the corresponding button. The random generation will be emphasized by a mechanism similar to a slot machine that will spin and then stop on the number of the anchor. The slot machine will have three “wheels”, each with a single digit. In case that the slot machine shows “000”, the anchor will be 1000, which will be told the participants in the instructions. The anchors will therefore range from 1 to 1000. All the objects fall within this range in their size in meters as well. After the first part of the study, which will present the comparison questions, participants will make an absolute judgment for size of each object in meters. Python script used to run the experiment is provided in Files. **Analysis** The anchoring effect will be tested using the effect of an anchor on the absolute judgment. Mixed-effect regression with absolute judgment as the dependent variable and anchor as the independent variable will be used in analysis. Random intercepts for participants and items will be included in the model. Random slopes for the anchor value for items will be also included in the model to take into account that the anchoring effect can differ between items. The interaction of the trial number with the anchor value will serve as a predictor in an exploratory analysis examining the effect of order of the questions on the anchoring effect. Answers higher than 3000 will be excluded as outliers.
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