Asking follow-up probes for selected responses in survey scales can affect responses to these items.

Having follow-up free response probes after forced choice survey questions allows researchers to assess the validity of the original choices. This can also be useful when psychological scales are administered as screening tools. The follow-up probes can be used to help decide if further diagnostic tests should be administered. A binary version of the General Health Questionnaire (GHQ-12) was given to an online sample (n = 1,048). Half answered the twelve GHQ questions in a binary format without follow-up probes. Half were asked with follow-up probes if they provided the psychologically concerning response. Those in the probe condition reported fewer psychologically concerning responses than those in the control condition. The difference between the probe and control groups increased as the survey went on. Researchers should be cautious comparing results from surveys that use selective follow-up probes with results from surveys that do not.