(a) The participant tests negative for HIV, then acquires HIV (black arrow) and tests positive for HIV prior to the survey. At the time of the survey, this participant accurately perceives himself to be HIV-positive. (b) The participant tests negative for HIV and remains HIV-negative. At the time of the survey, this participant accurately perceives himself to be HIV-negative. (c) The participant tests negative for HIV once in the past, then acquires HIV but does not have another HIV test prior to the survey. At the time of the survey, the participant inaccurately perceives himself to be HIV-negative.