The vast majority of surveys use ordinal answer formats independently of the construct under study. We hypothesise that the ordinal scale is not optimal under all circumstances, but that the suitability of answer formats depends on the construct measured. A repeat measurement study is conducted using binary and ordinal answer formats measuring two different constructs: attitudes and behavioural intentions. A clear interaction effect between answer formats and constructs is revealed, supporting the notion that there is not a single optimal answer format, but that some constructs are naturally more suitable for certain answer formats than others. These findings call for increased use of pre-studies to determine the optimal answer format before fieldwork rather then relying on standard answer formats.