 13. Personality in Adolescence  315
parenting (Van Leeuwen et al., 2007), or re -
lationships with peers (Borghuis et al., 2017). 
Although this research has flourished, there 
is no consensus on a model describing the 
psychologically meaningful characteristics 
of environments.
More recently, however, independent re -
search groups have started to examine the 
defining characteristics of environments to 
be in a better position to study trait–  situation 
transactions. There is now starting conver -
gence on situational models such as the Situ -
ational Eight DIAMONDS (  Rauthmann et 
al., 2014) or CAPTION (Parrigon, Woo, 
Tay, & Wang, 2017) models that may help 
to identify psychological attributes that in 
association with trait-based characteristics 
may advance our understanding of how de -
velopment occurs and influences important 
outcomes in life. The DIAMONDS model 
distinguishes eight dimensions to describe 
situation perceptions: Duty, Intellect, Ad -
versity, Mating, pOsitivity, Negativity, De -
ception, and Sociability. The CAPTION 
model includes seven: Complexity, Adversi -
ty, Positive Valence, Typicality, Importance, 
humOr, and Negative Valence. More recent -
ly, Rauthmann and Sherman (2018) reported 
convergent correlations between .47 and .69 
for five replicable dimensions across the two 
models: I. Negative Valence (CAPTION) 
versus Adversity (DIAMONDS); II. Adver -
sity (CAPTION) versus Negativity (DIA -
MONDS); III. Importance (CAPTION) 
versus Duty (DIAMONDS); IV: Complexity 
(CAPTION) versus Intellect (DIAMONDS); 
and V. Positive Valence (DIAMONDS) ver -
sus pOsitivity (CAPTION). Including short 
measures of these situational characteristics 
in longitudinal research on personality, and 
especially during adolescence, is likely to 
enrich our knowledge on how personality 
traits develop.
A second innovation that is likely to im -
pact personality studies in adolescence is the 
study of within-  individual trait variability . 
Until a decade ago, research on personality 
variability was almost exclusively oriented 
toward the investigation of between-  person 
differences (Fleeson & Jayawickreme, 2015; 
Jayawickreme, Zachry, & Fleeson, 2019). 
Nowadays, it is also clear that in addition 
to between-  individual differences, there are 
also substantial and important differences within the person, that is, how the indi -
vidual is changing or fluctuating feelings, 
thoughts, and behaviors during the day, also 
called personality states . This kind of vari -
ability has been largely ignored in previous 
research and has typically been treated as 
error—that is, in personality assessment, 
researchers usually aggregate scores across 
different items, using this aggregate (typi -
cally a mean) as an indicator of the trait. 
Variation in responses across individual 
items (or over time) is not used. This practice 
has been quickly changing in the study of 
traits in adults, which typically demonstrate 
that half of the variance is situated within 
the person (Debusscher, Hofmans, & De 
Fruyt, 2016; Minbashian & Luppino, 2014). 
These innovative methodologies have also 
quickly found their way to the study of per -
sonality pathology given that core features 
of the borderline personality disorder, for 
example, have a substantial within-  person 
affective dynamic.
The study of within-  individual trait vari -
ability in adolescents, using experience- 
sampling designs or alternative item re -
sponse theory (IRT)-based methods to 
delineate trait variance within the person 
from Likert-  based assessments conducted 
at a single moment in time (Lang, Lievens, 
De Fruyt, Zettler, & Tackett, 2019), will 
dramatically change our thinking about 
personality in adolescence. Questions at 
stake are how within-  person variability in 
traits develops across time, how much of 
the variance is within the person relative 
to between-  person differences, what are 
the determinants of within-  personal vari -
ability, and finally how such within-  person 
variability connects to outcomes that matter 
for adolescents, ranging from quality of life 
to educational achievement. The increasing 
possibilities provided by different forms of 
ambulatory assessments (Carpenter, Wy -
coff, & Trull, 2016; Trull & Ebner-  Priemer, 
2013; see also Mehl & Wrzus, Chapter 39, 
this volume) will dramatically advance our 
knowledge on the within-  person dynamics 
of personality over short periods. Wearable 
electronic devices, for example, may on a 
daily basis directly register activity level and 
record neurophysiological indicators of per -
sonality constructs, whereas cameras and/or 
audio devices may capture random samples 