Hawthorne effect

This when subjects in a study or experiment behave differently because they know they are being observed. For example in an educational or work setting, subjects may pay more attention to a task when they know they are being watched and recorded. This may simply life or depress oerall performace, but is particlarly problematic when it casues bias, in particular, if subjects are aware that the pwerson organising the study or observing the study has an interest in a particular outcome. In user studies this often occurs when new software is being trialed. Subjects may try harder at the favoured system, or give better subjcetive assessments, just to be nice.