Perceptual Aberration Scale (PAS)

Thirty-five true-or-false statements describe unusual experiences of perception and of one's own body: feeling that parts of the body have changed size or shape, that one's body is not one's own or that it is merging with objects, that sounds are unusually loud or distant, or that the surroundings look strange or unreal. Most items concern the body image, and some concern other perceptual changes.

Chapman, Chapman and Raulin (1978) developed the scale in the Wisconsin research program on psychosis proneness, following Meehl (1962), who proposed that subtle changes in bodily and perceptual experience might be one sign of vulnerability to schizophrenia. A long-term follow-up found that people with high scores, especially together with high magical ideation, were more likely to develop psychotic disorders (Chapman et al., 1994).

Statements answered in the keyed direction are counted. Higher totals describe more frequent unusual perceptual and body experiences; lower totals describe few such experiences. Such experiences also occur with fatigue, substance use, anxiety and other circumstances, so a high score describes an experience pattern and not a diagnosis.

The scale is used in research on schizotypy and psychosis risk, and in clinical assessment by professionals. On this site, the Magical Ideation Scale describes unusual beliefs from the same tradition, the Dissociative Experiences Scale (DES-II) describes depersonalization and related experiences, and the Revised Physical Anhedonia Scale describes reduced sensory pleasure.

The scale is administered only via a clinician patient link on this platform, and elevations are research indicators for follow-up rather than diagnoses.

The Perceptual Aberration Scale measures unusual experiences of one's body and perception, and it is a positive schizotypy measure within the Wisconsin Schizotypy Scales (Chapman et al., 1978; Kwapil et al., 2008). People with high scores, especially those who also reported magical ideation, were more likely to develop psychotic disorders over ten years (Chapman et al., 1994).

Factor analyses place it on a positive schizotypy factor that is separate from the negative schizotypy factor defined by the anhedonia scales, and the two factors predict different outcomes (Kwapil et al., 2008).

“I sometimes have had the feeling that some parts of my body are not attached to the same person.”

Illustrative only. During administration items are presented one screen-set at a time; response-key direction is never shown to respondents.

Item responses are summed within each scale (reverse-keyed items recoded first) and expressed as a percent of the maximum possible score. No normative percentile is applied — there is no verbatim-matched published norm for this exact item set.