810 vIII. EMERGING  ISSuES AND  NEW  DIRECTIONS
quent experience for most people, whereas 
emotional states are thought to be continu -
ous. To capture infrequent experiences (e.g., 
conflicts), either more frequent assessments 
or event-  contingent sampling is advisable. 
Furthermore, such studies need to last longer 
(i.e., cover more days or weeks) to increase 
the chances of capturing rare phenomena 
compared to studies on frequent or continu -
ous phenomena (e.g., positive mood). In gen -
eral, assessments should be frequent enough 
to catch the target phenomenon, yet sparse 
and short enough to limit response burden. 
Break days with no assessments within a 
study enable longer total monitoring periods 
by reducing participants’ burden. Still, the 
sampled situations and days should repre -
sent the situations that researchers seek to 
generalize to, for example, weekdays and/or 
weekends and times when people are typi -
cally at work or not (e.g., Wrzus, Wagner, & 
Riediger, 2014).
Technical  Implementation
Currently, most experience sampling and 
daily diary assessments are implemented 
on mobile platforms (Bolger & Laurenceau, 
2013; Pejovic, Lathia, Mascolo, & Musole -
si, 2016; Thai & Page-Gould, 2018). Often 
dedicated experience sampling programs or 
apps (e.g., ExperienceSampler, Expimetrics, 
mEMA, mobileQ, movisensXS, PocketLab) 
are installed on mobile devices that control 
the assessment schedule, deliver the ques -
tions to participants, and store the data on 
the device or upload them to an external 
server. Alternatively, participants may use 
commercial or free online-  survey software 
(e.g., LimeSurvey; SoSciSurvey; see www.
websm.org  for a broad overview of software 
solutions), so that participants repeatedly 
receive e-mails with links to the Web-based 
questionnaire. The drawback is that partici -
pants must always have an active Internet 
connection to answer the questionnaire.
Researchers can either rely on partici -
pants’ own devices or provide participants 
with dedicated research devices. Purchasing 
the same device for all participants ensures 
that the questionnaire looks and functions 
identically for all participants. In addition, 
further applications may be blocked (e.g., 
calls), which is not possible with partici -
pants’ devices. The disadvantages of pur -chasing devices are financial costs and the 
quick obsolescence of technical standards. 
Using participants’ devices, such as smart -
phones, is a low-cost and flexible solution, 
but it has at least two caveats: The appear -
ance and perhaps functionality may vary 
between devices, which possibly affects the 
comparability of the study conditions, and 
samples may be selective if the smartphone 
owners differ by sociodemographic char -
acteristics, socioeconomic status, or even 
personality (Lane & Manner, 2011). Yet the 
increasing prevalence of smartphones world -
wide will gradually minimize these method -
ological concerns. For further information 
on technical solutions, see Wrzus and Mehl 
(2015) or www.ambulatory-  assessment.
org.
State Variability as  Contribution 
to Personality  Research
Experience sampling studies have contribut -
ed greatly to the understanding of personal -
ity processes. For example, in their seminal 
work, Fleeson (2001; Fleeson & Gallagher, 
2009) examined how self-  reported personal -
ity states vary in daily life. They assessed per -
sonality states up to five times a day, general -
ly for 2 or 3 weeks with handheld computers 
or sometimes paper-and-  pencil question -
naires. Despite the considerable variability of 
personality states in daily life, the mean per -
sonality state correlated highly with general 
trait self-  perceptions (Fleeson, 2001; Flee -
son & Gallagher, 2009). In addition, both 
the mean and the variability of personality 
states showed considerable stability across 2 
or 3 weeks, which indicates that how people 
experience themselves on average and how 
much they vary in their experiences can be 
seen as individual characteristics with at least 
some temporal stability (Fleeson, 2001). In 
2017, the Journal of Research in Personality 
dedicated a special issue on personality state 
variability as a unique phenomenon that can 
be explained by situational and trait factors 
(Vazire & Sherman, 2017).
Traits and  Situation Perceptions  
as Predictors of  States
Sherman and colleagues (2015) examined 
how personality traits predict the percep -
tion of situations, and how both traits and 