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Description: The Objective Numeracy Scale (ONS) contains eight items aimed at assessing individual differences in numeracy, or the ability to understand, manipulate, and use numerical information. These differences often relate to decisions and decision-related processes, such as perceived risk and graph/chart comprehension. The ONS was developed from a larger pool of items including those used in pre-existing numeracy scales and was found to predict decision-making performance, supporting its predictive validity. It has been tested against previous numeracy scales, and performs comparatively, if not better than these past measures (Weller et al., 2012). This scale has undergone several revisions. See below for updates. Scale Update (02/2016): Please note that the last two questions, 7. and 8., are well known on Mechanical Turk. Items from Toplak, West, and Stanovich (2014) have been used as substitutes for those questions when administering the scale on MTurk. (Toplak, M., West, R., & Stanovich, K. (2014). Assessing miserly information processiong: An expansion of the Cognitive Reflection Test. Thinking & Reasoning, 20(2), 147-168.) Scale Update (06/2014): Please note that we adjusted the list of accepted answers for most of the items. Many of these newly accepted answers include alternative formats to previously accepted answers. Further commentary is included in the material document. Scale Update (02/2013): Please note that we adjusted the mammogram item on the numeracy scale to reduce guessing and improve the scale further (i.e., before the answer to the item was 1/2). There is evidence suggesting that when people do not know the answer to a probability judgment their answer is 1/2 or 50% (Fischhoff & Bruine de Bruin, 1999).