 38. Personality Interventions  801
plan to engage in those activities (Lejuez, 
Hopko, & Hopko, 2001). The goal of be -
havioral activation therapy is similar to the 
proposed mechanisms of personality change 
in which the immediate aim is to alter per -
sonality states, but importantly, these states 
are made explicit and necessitate acknowl -
edging the value in changing states, going so 
far as creating a plan to continue the shifts 
in states.
How Long Should Interventions  Be?
Most dominant personality theories do little 
to explain continuity and change in person -
ality during the time course typically found 
in interventions, as these theories are framed 
in terms of years and decades rather than 
the weeks to months time frame typical of 
interventions. Just how fast can personality 
change? Short-term interventions are likely 
to be more effective for prompting effort -
ful processes such as cognitive reframing 
or situation manipulation, but perhaps not 
lasting personality change. Personality in -
terventions attempt to provide the means or 
skills for people to change their behavior, 
thoughts, and feelings, but the changes most 
likely are not natural and effortless, instead 
taking energy and awareness to implement. 
As a result, prolonged behavioral changes 
are likely to take time. Similar to learning 
a second language but not practicing it for 
years, it is also likely that interventions need 
follow-  up or booster interventions to keep 
learned skills sharp. Ideally, an intervention 
should provide a long-term skill, similar to 
riding a bike, so that once that skill is ac -
quired, it is always there, with no additional 
training or booster sessions necessary. But 
it currently is not clear what length of inter -
vention would accomplish this goal, as dose 
effects have not been systematically exam -
ined.
Contrasting the notion of lengthy inter -
ventions is the effectiveness of short thera -
peutic interventions (Roberts et al., 2017). 
Notably, there was a nonlinear relationship 
between the length of intervention and its 
impact on personality, with intervention 
effectiveness leveling off at approximately 
2 months (Roberts et al., 2017). However, 
there is a possibility that the effectiveness 
of a short-term intervention is due to patho -plastic effects, whereby elevated levels of the 
trait are due to the circumstances that lead 
someone to enter into therapy in the first 
place (Noordhof, Kamphuis, Sellbom, Ei -
genhuis, & Bagby, 2018). Reverting back to 
one’s “set point” or ridding oneself of exter -
nal factors that led to temporary changes in 
personality would not constitute a success -
ful personality intervention.
What Age Is Most Effective for  Interventions?
Early interventions are often priorities, be -
cause children are thought to be more mal -
leable (due to fewer environmental con -
straints and other factors), and because their 
life paths have not yet congealed toward a 
particular direction, which tends to hap -
pen after education, occupation, and family 
choices are made. As a result, many advocate 
that early childhood interventions should be 
prioritized (Heckman, 2006). Overall, early 
school, family, and antisocial interventions 
suggest that interventions could be effective 
for personality-  related outcomes. However, 
a number of the processes thought to drive 
personality trait change rely on changes to 
the self-  concept, and an ability to be moti -
vated towards an end goal. These proposed 
prerequisites may be difficult to accomplish 
for children, especially preschool- age chil -
dren. In contrast, adults and older adults 
have a more set identity and a lifestyle that 
is entrenched by decades of familiarity.
Conclusion
If a person is unhappy with his or her per -
sonality, it is currently not possible to pro -
vide a solution with a well-  validated inter -
vention. Although there is promise across 
a diverse range of interventions, lacking is 
any preregistered randomized controlled 
trial (RCT) that adheres to Consolidated 
Standards of Reporting Trials (CONSORT) 
guidelines, which currently serve as the gold 
standard for intervention evaluation. The 
multiple types of interventions we have re -
viewed indicate that future editions of this 
handbook will likely provide clearer guide -
lines for the person who is unhappy with his 
or her personality. To make this a reality, 
more research attempting to change person -