 30. Attachment Theory and Personality  657
cedence in early childhood, then give way to 
selection dynamics as individuals develop. 
One consequence of this inequality is that 
recent experiences are more influential than 
distal experiences in shaping psychological 
outcomes. But distal experiences that take 
place in early childhood in particular (i.e., 
when socialization effects dominate) are 
more powerful than distal experiences that 
take place later.
We illustrate these developmental prin -
ciples with an empirical example concerning 
parental divorce. Many scholars have stud -
ied the impact of parental divorce on chil -
dren, because the context of divorce (both 
the events that precede it and those that fol -
low it) often includes disruptions in the sta -
bility of the caregiving environment (Feeney 
& Monin, 2016). Research generally finds 
that children from divorced families experi -
ence more difficulties in psychological func -
tioning. Because divorce is a reasonably dis -
crete event, one can ask whether the timing 
of parental divorce matters in its relation to 
attachment functioning.
Fraley and Heffernan (2013) addressed 
this question in two large samples of adults. 
They found that at the time of assessment, 
adults were more insecure in their relation -
ships with their parents if their parents had 
been recently divorced; that is, adults whose 
parents had divorced in the recent past were 
less likely to report that they had a secure 
relationship with their parents than those 
whose parents had divorced in the distant 
past. However, after controlling for how 
long ago the divorce took place, Fraley and 
Heffernan found that the timing of the di -
vorce mattered, too: When parents divorced 
early in their children’s lives (e.g., before the 
age of 5), those adult children were less se -
cure in their current relationships with their 
parents than those whose parents divorced 
later in their children’s lives. Stated differ -
ently, divorces that took place 20 years ago 
were less tied to current functioning than 
divorces that took place 20 months ago. 
But divorces that took place 20 years ago in 
early childhood  were more influential than 
divorces that took place 20 years ago in later 
childhood.
These results suggest that both primacy 
and recency effects should be considered 
when studying the ways in which interper -sonal experiences may shape the long-term 
development of attachment styles. People’s 
current interpersonal context is the best 
candidate for understanding why people are 
secure or insecure in the here and now. And 
the further back one reaches, the less influ -
ential those distal experiences should be. 
But there is one potential exception: Experi -
ences that take place in early childhood may 
be more powerful than similar experiences 
that take place later. That does not mean the 
effects are strong in an absolute sense, but 
their traces should be persistent.
Behavior Genetics and Adult Attachment
It is well-known that most individual- 
difference constructs are heritable. Using 
twin designs, researchers have found that 
about half of the differences between people 
in traits such as agreeableness or neuroti -
cism can be accounted for by genetic differ -
ences between persons (Bleidorn, Kandler, 
& Caspi, 2014).
To date, a few studies have used twin de -
signs to estimate the relative contribution 
of genetic, shared environmental, and non -
shared environmental sources of variance to 
individual differences in adult attachment 
styles (Brussoni, Jang, Livesley, & Macbeth, 
2000; Crawford et al., 2007; Donnellan, 
Burt, Levendosky, & Klump, 2008; Franz 
et al., 2011). The results vary across studies 
in part because they do not measure attach -
ment in a consistent way. But the two studies 
(Donnellan et al., 2008; Franz et al., 2011) 
that used measures that most closely align 
with the multi-item scales commonly used in 
contemporary attachment research suggest 
that there is a sizable role (about 27–45%) 
for heritable variance in adult attachment. 
And, similar to the findings in the person -
ality literature more broadly, there is little 
evidence that shared environmental factors 
(i.e., factors that are shared by twins grow -
ing up in the same family) contribute to indi -
vidual differences in attachment style.
What are the implications of these find -
ings? If we take them at face value, they 
suggest that what makes some people se -
cure in their relationships reflects, at least in 
part, genetic differences among people. One 
source of controversy, however, is whether 
such estimates conflict with the assump -