Straight-lining
Also called non-differentiation
Selecting the same answer across every row of a question battery.
In a matrix of ten statements, a respondent who selects “Agree” for all ten may genuinely agree with all ten. They may also have found the fastest route to the next page. The pattern is a flag, not a verdict, and it is most informative when the battery contains items nobody could consistently endorse.
The design fix comes first: shorter matrices, fewer of them, and items that are not near-duplicates of each other. Straight-lining is partly a measure of how tiring your questionnaire is.
Read it beside timing. A battery answered identically in four seconds is a different case from one answered identically in ninety.
Where it goes wrong
Excluding straight-liners from a survey whose items all point the same way. On a well-made agreement battery, genuine agreement looks exactly like this.