Background: The problems associated with people interaction within a couple is one of the principal causes for consultations in individual psychotherapy. The Dyadic Adjustment Scale (DAS; J Marriage Fam 38 (1976) 15-28) is regarded as the most used evaluation tool of marital adjustment. To date, however, there is no fully satisfactory version of the test, either because the revised versions have undergone an over simplification of the underlying model, or the revised versions have remained faithful to the postulates of the DAS but have not been fully validated. Moreover, from a clinical point of view, marital therapy must be associated with the analysis of both convergences and divergences between the adjustment of each partner. Hence, the DAS could be viewed as a tool that is particularly adapted to such an evaluation. Nevertheless, a precise analysis of DAS is required in order to grasp both the individual profiles and the pattern differences between the individuals.

Design of the study: We conducted a series of studies with the aim to (1) test once more the limits of the original DAS structure and, (2) identify a simple structure for the tool through exploratory factor analysis. First, we showed that our analyses provided the possibility to simplify the inventory. Hence, it was possible to decrease the number of scales as well as the number of items used. Contrary to the unidimensional tendency and the extreme simplification of the number of items, we were able to identify furthermore the precise constructs taken into account by the DAS, and to proceed in a rigorous and validated analysis of two distinct samples. Second, we examined the stability of the structure according to the sex of both respondents. Finally, we checked the relevance of this factorial structure for the better understanding of the differences between partner interactions within the couple. Participants' data were collected from a sample of 123 couples. Results showed that the structure reported by Spanier is not replicated. After a first elimination of items on criteria of asymmetry and a weak capacity for discrimination, we ran factor analysis with the answers of the sub sample of validation. We chose principal components analysis with orthogonal rotations in order to identify the most independent constructs. Sixteen items were preserved.

Results: Results showed that they were organized according to two dimensions that explain 52% of the variance. The first factor relates to the degree of agreement in couples (DA). Ten items present loadings with this component explaining 32% of the variance. The second dimension, made up of six items, corresponds to the quality of the dyadic interactions (IQ). This factor explains 20% of the variance. The correlation between the scales that were derived from this analysis was found to be r=0.50 (p<0.01). The cross-validation analysis performed on the subjects' answers was found to follow the same factorial structure, just as the male and female samples did. Our analyses further highlighted the relevance of a hierarchical structure and consequently, the possibility of calculating a total score. The coefficients of internal consistency were 0.89 for the total scale and the scale of degree of agreement, and 0.75 for the scale of quality of the interactions. As the DAS-16 was strongly correlated with the full DAS version, the possibility of score equivalence was thus confirmed. In conclusion, our results provide a unidimensional structure and a two-dimensional comprehension of marital adjustments. The factors were shown to be stable and similar for sex. Moreover, one of the weaknesses of the original version of the DAS was the lack of independence of the scales. Our version of the DAS allows the identification of factors that are moderately correlated. Finally, one of the originalities of our work is the validation of the abbreviated form that used as indicator the differences between partner interactions within a given couple.