806 
Traditionally, personality is assessed via self- 
report questionnaires that tap into how indi -
viduals generally see themselves with respect 
to their thoughts, feelings, and behaviors. 
For example, when participants are asked to 
rate the degree to which they worry or keep 
things neat and tidy, they search their mem -
ories for relevant experiences and behaviors 
in their lives, and integrate them into a rat -
ing of what they deem characteristic of them. 
This approach to measuring personality is 
very efficient and has been highly useful in 
predicting real-world outcomes. However, 
when possible, it seems informative to (also) 
assess personality directly in daily life; that 
is, researchers should measure directly how 
much people worry and how they organize 
their belongings in vivo and in situ . In this 
chapter, we argue that such ecological as -
sessments are fundamentally important for 
the field of personality psychology. Over the 
last two decades, the development of mod -
ern methods for accomplishing this has been 
spurred by society-  changing developments 
in mobile technologies and the diffusion of 
smartphones and wearables into every pore 
of our lives.
In line with current theorizing around the 
measurement of personality, in this chapter we review ecological approaches for study -
ing experiences, behaviors, and situations in 
daily life (Figure 39.1).  Assessment of situ -
ations is included, because understanding 
situational characteristics is critical for un -
derstanding the effects of personality (Furr 
& Funder, Chapter 31, this volume). The 
reviewed methods are referred to as ambu -
latory assessment  (Carpenter, Wycoff, & 
Trull, 2016; Trull & Ebner-  Priemer, 2014), 
ecological momentary assessment  (Smyth & 
Heron, 2014), experience sampling  (Hekt-
ner, Schmidt, & Csikszentmihalyi, 2007), 
and diary methods  (Bolger, Davis, & Rafa -
eli, 2003). At their core, they allow research -
ers to study individuals (1) in their natural 
settings, (2) in (close to) real time, and (3) on 
repeated occasions (i.e., “real-world,” “real-
time,” “within-  person”).1
Rationale for Studying Personality in Its 
Natural  Habitat
Research methods for studying daily life de -
rive their rationale from their three unique 
measurement characteristics: studying indi -
viduals (1) in everyday settings, (2) in (close 
to) real time, and (3) on multiple occasions CHAPTER 39
Ecological Sampling Methods  
for Studying Personality in  Daily Life
Matthias R. Mehl  
Cornelia Wrzus