SHORTENED VERSIONS OF THE INTERPERSONAL SENSITIVITY MEASURE, PARENTALBONDING INSTRUMENT AND INTIMATE BOND MEASURE

A questionnaire sent in 1990 to over 2000 pairs of 18 to 26-year-old t wins included shortened versions of the Interpersonal Sensitivity Meas ure (IPSM), Parental Bonding Instrument (PBI) and Intimate Bond Measur e (IBM). To evaluate the validity of these short scales, and investiga te their stability over time, full versions of the questionnaires were mailed 1 year later? in 1991, to a subsample of 100 twin pairs (25 mo nozygotic females, 25 monozygotic males, 25 dizygotic females, 25 dizy gotic males). After follow-up, replies were received from 51 male and 70 female individuals (60% response overall). From the full length que stionnaires used in 1998 we were able to generate test scores for both the shortened and full scale versions, whereas from the 1990 study on ly short scale scores were available. Correlations between the shorten ed and full length scales obtained in 1991 were high (r = 0.64-0.99). Correlations between test scores on the shortened versions of the inst ruments in 1990 and 1991 were moderate (r = 0.47-0.55) for the IPSM, a nd slightly higher for the shortened PBI scales (0.55-0.66) and the sh ortened IBM care subscale (r = 0.58). Correlations between the 1990 sh ortened scales with their full length 1991 counterparts were slightly lower for the IPSM (r = 0.31-0.50), comparable or slightly higher for the PBI (r = 0.61-0.70), and the same for the IBM (r = 0.58). Internal reliabilities of the shortened test versions were slightly reduced bu t satisfactory in most cases when compared with the full instruments: Cronbach's alpha full length 1991 alpha = 0.81-0.96; shortened 1991 al pha = 0.46-0.96; shortened 1990 alpha = 0.48-0.96. We conclude that so me information is lost using the shortened versions of these instrumen ts, and there is also some change over time. However, the relationship between the tests, using either the full length versions or the short ened counterparts, remained constant suggesting that the shortened ver sions can be used in epidemiological studies.