In this paper, we use a category follow up probe administered to respondents who initially select the mid-point in the 9-point left-right scale, to determine whether they selected this alternative in order to indicate a distinct opinion, or to indicate that they do not have an opinion on the issue (position). We find in the cross-section CATI- and in an access panel survey that the vast majority of the middle category responses turn out to be 'don't knows' and that reallocating these responses from the mid-point to the don't know category significantly alters descriptive inferences. Our findings have important implications for the design and analysis of bipolar rating scales especially of the left-right political orientation scale.