Inclusion Criteria:  age of at least 18 years normal cognitive function at the time of enrollment evidenced by a Mini-Mental State Examination (MMSE) score of more than 24 of 30 Chinese Mandarin as the native language providing informed consent  Exclusion Criteria:  pre-existing delirium assessed according to the Confusion Assessment Method (CAM) history of neurological or psychiatric disease impaired vision or auditory function which may effect the assessments unwillingness to participate in the study