INTERPERSONAL RELATIONS AND GROUP PROCESSES

DAVID T. LYKKEN AND AUKE TELLEGEN

Table 3

Similarity of the Spouses of Pairs of Monozygotic (O[nd) and Dizygotic (DZ) Minnesota Twin
Registry Participants on 10 Attributes

TVote. The twin-spouse correlations for these 538 spousal pairs are included for comparison. LTI =
leisure time interest factor; ATT = attitude items; MPQ = Multidimensional Personality Questionnaire
scale.

^, Well-Being, Social Potency, Achievement, Social Closeness, Stress Reaction, Alienation, Aggression,
Control, Harm Avoidance, and Absorption.

unrelated individuals will show similar scores on some of this
diverse set of 74 psychological factor scores just by chance; on
the average, each random pair will differ by less than five T
score units on about 10 of the 74 dimensions. Pairs of individ-
uals who were selected as spouses of MZ twin pairs show no

Figure 1. Log-log plots of the number of variables (totaling 74) that
show the mean absolute differences in T score units (M = 50, SD = 10)
sown on the X axis. (Data are given for pairs of monozygotic (MZ)
twins, for random pairs of unrelated persons, and for pairs of spouses
of MZ or dizygotic (DZ) twin pairs. For each pair, the 74 absolute
differences were rank ordered before being averaged over pairs of the
given type. The figure shows that, although pairs of MZ twins produce
very similar scores on many variables, differing by less than 0.5 stan-
dard deviations on nearly half of them, the spouses of MZ twins show
no more small within-pair differences than the spouses of DZ twins or
than random same-sex pairs.)

more similaΛcores than do DZ spouse-spouse pairs and
hardly more than do random pairs of same-sex adults.

The idiographic model of mate selection predicts (a) that
each individual chooses a mate according to some idiosyncratic
small set of criteria, (b) that MZ twins are likely to use similar
criteria, and therefore, (c) that MZ spouse-spouse pairs, while
not remarkably similar in all or most respects, will tend to be
very similar in at least a few respects. We have tested this final
prediction with respect to a wide range of potential psychologi-
cal criteria and with negative results.

Study 3: Twins’ Evaluation of Their Cotwins’ Choices

Yet another test of whether mate selection is lawful versus
adventitious would be to simply ask adult twins to evaluate the
choices, including mate selections, made by their cotwins. If
choice behavior is lawfully influenced by characteristics of the
chooser, then twins should tend to approve of their cotwin’s
choices or should indicate that they are similar to the choices
they themselves have made or would make. Moreover, MZ
twins should endorse their cotwin’s choices more frequently
than do DZ twins on the average. If we also ask the twins to
report how they felt about the cotwin’s choice of a mate (at or
about the time of the cotwin’s marriage when we can be reason-
ably sure that the cotwin was under the impression that the
right choice had been made), then the data will permit us to
estimate whether mate selection is about as lawfully dependent
on the characteristics of the chooser as are the other types of
choices sampled. We cannot expect even MZ twins to feel about
their cotwin’s fiances and fiancees as positively as their cotwins
do; even MZ twins are not identical psychologically, and each
twin is likely to know his or her spouse-to-be better than the

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