632 vI. SELF‑ AND S OCIAL P ROCESSES
recollections of parenting. Thus, we tend to 
favor prospective longitudinal designs for 
shedding light on the parenting correlates of 
narcissistic attributes. We are aware of only 
three such studies.
Cramer (2011) provided one of the first 
longitudinal investigations of the develop -
mental correlates of narcissism using data 
from the Block and Block (1980) sample. 
Cramer (2011) drew a distinction between 
adaptive narcissism (autonomy) and mal -
adaptive narcissism (willfulness and hyper -
sensitivity). Willfulness in this study is likely 
a blend of grandiosity and entitlement from 
the NSM, and hypersensitivity is akin to 
vulnerability from the NSM. Adaptive nar -
cissism seems to share attributes with the 
leadership/authority elements of the Nar -
cissistic Personality Inventory (Raskin & 
Terry, 1988). Early parenting responsive to 
the needs of the child was associated with 
adaptive narcissism at age 23. There were no 
parenting main effects on maladaptive nar -
cissism at age 23; however, Cramer (2011) 
found an interaction between age 3 precur -
sors to narcissism and parenting when pre -
dicting maladaptive narcissism at age 23. 
Specifically, developmentally inappropriate 
parenting (e.g., lacking in responsiveness 
early in development or being too indulgent 
in adolescence) interacted with temperamen -
tal attributes to predict maladaptive narcis -
sism, particularly mother–  child parenting 
variables. These findings, although based on 
a small sample (the maximum sample size 
was less than 100), suggest that transactions 
between early emerging individual differ -
ences and parenting play a role in the etiol -
ogy of narcissistic attributes.
Brummelman et al. (2015) conducted a 
four-wave longitudinal study ( N = 565) of 
parental overvaluation and narcissism (as -
sessed as a unidimensional construct) with 
a 6-month time interval between waves. 
Parents reported on their level of overvalu -
ation and children (age range = 7–11 years 
at Wave 1) reported on their levels of nar -
cissism using the Child Narcissism Scale 
(Thomaes, Stegge, Bushman, Olthof, & 
Denissen, 2008). Although both constructs 
were highly stable over time, parental over -
valuation prospectively predicted child nar -
cissism, even after researchers controlled for 
prior levels of narcissism (standardized co -efficients around .06–.07). Brummelman et 
al. (2015) concluded that “collective efforts 
to reduce parental overvaluation . . . hold 
promise in curbing the societal rise in nar -
cissism” (p.  3661).
Wetzel and Robins (2016) have reported 
the largest longitudinal study of the develop -
ment of narcissistic attributes using a sample 
of 674 Mexican-  origin youth followed from 
ages 12–16. They measured parental hostil -
ity and monitoring, along with two aspects 
of narcissism—  superiority (essentially adap -
tive aspects of narcissism) and exploitative -
ness (akin to entitlement in the NSM). Par -
enting variables were measured using child 
reports, spouse reports, and observational 
coding. The most consistent results were that 
increased parental hostility and decreased 
monitoring were associated with exploit -
ativeness, even after researchers controlled 
for its shared variance with self-  esteem.
One issue that many existing developmen -
tal theories about the origins of narcissism 
will eventually need to address is the reality 
of genetic influences (see Holtzman & Don -
nellan, 2015). Regardless of the measure 
used to assess narcissism, heritability esti -
mates have been substantial in the behavior 
genetics literature. Vernon, Villani, Vickers, 
and Harris (2008) reported that the herita -
bility for NPI scores was 59%, with the re -
maining 41% of the variance attributable to 
nonshared environmental factors (and error) 
using a sample of 139 adult twin pairs from 
the United States and Canada. Similar re -
sults were reported by Luo, Cai, Sedikides, 
and Song (2014), who found a heritability 
estimate of .47 for the NPI using a sample of 
304 Chinese twins. Torgersen et al. (2012) 
reported heritability of .71 using a latent 
variable model of NPD with interview and 
self- reports as indicators based on data from 
2,794 adult Norwegian twin pairs (see also 
Jang, Livesley, Vernon, & Jackson, 1996). 
As with research on most personality attri -
butes in adult samples (see, e.g., Turkheimer, 
2000; Polderman et al., 2015; Vukasovi ć, & 
Bratko, 2015), there was no evidence for the 
effect of the shared environment in these 
studies of adults.
Researchers have only recently focused 
on specific elements of personality associ -
ated with NSM, and there are hints that 
the genetic architecture might be different 