 39. Ecological Sampling Methods  807
(Mehl & Conner, 2013). In the field of per -
sonality, these characteristics resonate with 
calls for studying “actual behavior” (Bau -
meister, Vohs, & Funder, 2007), conse -
quential outcomes (Ozer & Benet-  Martinez, 
2006), ordinary conduct or “quotidian per -
sonalities” (Craik, 1993), and temporal dy -
namics and personality processes (Fleeson, 
2001, 2007; Kuppens & Verduyn, 2017; 
Vazire & Sherman, 2017; van Zalk, Nestler, 
Geukes, Hutteman, & Back, 2020; Wrzus 
& Roberts, 2017).
Real‑World  Behavior
Research methods for studying daily life aim 
at capturing—  as closely, noninvasively, and 
contextually naturally as possible—  what ac -
tually happens in people’s lives (Reis, 2012). 
The methodological momentum comes from 
the insight that in prioritizing internal va -
lidity and experimental control, laboratory 
studies run the risk of producing causally 
isolated but contextually insulated results 
that can be of limited generalizability and 
applicability (Cialdini, 2009; Funder, 2009). 
Reis and Gosling (2010) argued that research 
methods outside the laboratory advance the field through their emphasis on the “three 
R’s” of external validity (Brewer, 2000): 
robustness (i.e., Does it replicate across set -
tings, populations, and circumstances?), 
representativeness (i.e., Is it typical for what 
actually happens in life?), and relevance 
(i.e., Does it matter for people’s lives?). And 
Brunswik (1956) pointed out that psycholo -
gy operates under a “double standard” when 
it applies sampling theory to participants 
but not to environmental conditions (Judd, 
Westfall, & Kenny, 2012). He argued that 
there is a need for representative research 
designs that sample participants randomly 
from underlying populations and situations 
from underlying ecologies to ensure the gen -
eralizability and applicability of findings. 
Ambulatory assessment methods employ 
such representative designs through their in -
termittent ecological response sampling.
The importance of measuring real-world 
behavior is evident in the phenomenon of 
white coat hypertension,  or the tendency 
for patients to have higher blood pressure 
readings at the doctor’s office than in their 
homes (Pickering et al., 1988). Moreover, in 
some cases, blood pressure readings at the 
doctor’s office can also underestimate daily Experience
Daily thoughts, 
feelings, and 
perceptions
Behavior
Daily social 
activities and 
interactionse.g., naturalistic observation (audio, visual),
mobile sensing (smartphones, wearables),
experience sampling
e.g., naturalistic obse rvation (audio, 
visual), mobile sensing (sma rtphone s, 
wearables), online social media 
(Facebook, Twitter),
experience samplingSituation
Daily physical 
and social 
environmente.g., experience  
sampling, daily diaries
FIGURE 39.1. Ecological sampling methods for studying personality in daily life.