800 vIII. EMERGING  ISSuES AND  NEW  DIRECTIONS
a trait-  consistent manner, as well as develop -
ing a more elaborate strategy that targeted 
specific traits (Allan, Leeson, De Fruyt, & 
Martin, 2018). Such targeted strategies that 
are specific to the individual can be easily 
delivered via instant messages or through 
apps. For example, the recently developed 
PEACH (PErsonality coACH) app assists 
with coaching via an artificial intelligence 
(AI)-assisted chat-bot to increase motiva -
tion and involvement (Stieger et al., 2018). 
Preliminary results suggest that the training 
app is effective in increasing openness and 
self- discipline over a 6-week period (Stieger 
et al., 2020).
Unanswered Questions 
and Future  Directions
The studies we have reviewed cover many 
different approaches to change personality. 
From early childhood-  based home interven -
tions to ingesting mushrooms, the strategies 
used to impart change range from chang -
ing the surrounding environment to chang -
ing behavior directly or indirectly related to 
personality, to changing thought processes, 
all the way to changing neurotransmitters. 
A sober conclusion relative to the reviewed 
studies suggests no clear way to change one’s 
personality. Of those interventions that 
found evidence of change, each has limita -
tions. For example, most studies lacked a 
representative sample or were selected be -
cause of some characteristic (e.g., disad -
vantaged or experiencing anxiety). Beyond 
selection bias, few studies looked systemati -
cally at how intervention length and follow- 
up period influenced findings, or whether 
personality assessed via different modali -
ties also evidenced change. As a result, it is 
difficult to say there is a known method to 
change personality. The lack of progress in 
identifying how to intervene on personality 
should not be too surprising, as few studies 
have explicitly attempted to change person -
ality. Moreover, intervening on any aspect 
of one’s psychology is difficult, as seen in 
related literatures (e.g., Kreplin, Farias, & 
Brazil, 2018; Sisk, Burgoyne, Sun, Butler, 
& Macnamara, 2018). Below we highlight 
three important questions that should guide 
future work.Which Experiences Are Needed 
to Change  Personality?
One difficulty in identifying which interven -
tions are effective is knowing the processes 
involved in personality change. It would be 
easier to create an effective intervention if 
one knew the reasons that drive personal -
ity change. Current thought is that chang -
es in personality come via an environment 
stimulus, which directly impacts state-level 
manifestations of personality, not trait levels 
(Roberts & Jackson, 2008; Wrusz & Rob -
erts, 2017). Thus, for the environment to en -
gender lasting changes in personality, shifts 
in states beyond what is typical in everyday 
life are necessary (Chapman et al., 2014; 
Magidson, Roberts, Collado-  Rodriguez, & 
Lejuez, 2014). Shifts in personality states 
then work through a “bottom-  up” process 
that eventually leads to lasting changes in the 
trait, in which the shifts in states feel natural 
and occur automatically. Shifts in states can 
come from expectations and contingencies 
in the environment, either through natu -
rally occurring environments such as one’s 
workplace or one that is purposely imposed, 
such as an intervention. This “fake it until 
to you make it” view in which personality 
states are shifted beyond typical levels can 
be seen as the motivating theory behind the 
self- control, cognitive, and coaching train -
ing interventions.
Given the lack of success in many of these 
training interventions, shifting states may be 
necessary but not sufficient to alter person -
ality. Will any shift in a state related to a 
trait over a period of time lead to change, 
or does some form of active participation 
need to occur? For how long does this need 
to occur? Factors such as being motivated 
to change, conscious awareness of shifting 
states, valuing the potential change, and 
having a set of skills to continue enacting 
state changes may also be necessary. An ex -
ample of taking some of these considerations 
into account can be seen in behavioral acti -
vation therapy (see Magidson et al., 2014, to 
see what this would look like in the context 
of a personality intervention). The focus of 
behavioral activation therapy is to identify 
which behaviors are consistent with one’s 
values or goals, identify the daily activities 
consistent with those values, and create a 