814 vIII. EMERGING  ISSuES AND  NEW  DIRECTIONS
& Rentfrow, 2014)—a sorely needed build -
ing block for this nascent field.
Online Social Media  Tracking
An ecological assessment method that is 
still relatively new is the tracking of online 
or “virtual” behavior through social media 
sites such as Facebook, Twitter, and You -
Tube (Gosling & Mason, 2015; Kosinski, 
Matz, Gosling, Popov, & Stillwell, 2015; 
Kulkarni et al., 2018; Kosinski, Wang, Lak -
karaju, & Leskovec, 2016; H. Schwartz & 
Ungar, 2015). For example, Biel and Gatica- 
Perez (2014) studied online self-  expressions 
through YouTube video blogs, or vlogs, a 
popular form of one-to-many communica -
tion in which individuals post short person -
al (amateur) videos to a community of fol -
lowers. Specifically, they investigated how 
viewers form personality impressions about 
vloggers based on audiovisual cues such as 
facial expressions, body postures, and ver -
bal content. As a critical methodological in -
novation, all vocal and behavioral cues were 
extracted from the videos via automatic sig -
nal processing, and the personality impres -
sions were crowdsourced via Mechanical 
Turk (MTurk), resulting in a dataset that is 
uniquely large for this area of research.
More recently, Youyou, Kosinski, and 
Stillwell (2015) studied Facebook Likes as 
one specific type of behavior. They demon -
strated that computer-  based judgments of 
personality, based entirely on patterns of 
Facebook Likes (often not more than 100) 
were more accurate in predicting life out -
comes than informant reports and, in some 
cases, even more accurate than self-  reports 
(e.g., participants’ social network activity). 
Park et al. (2015) found a similar advan -
tage of computer-  based personality models 
over human personality judgments when 
the computer-  based models were derived 
from text analyses of participants’ word use 
in their Facebook status updates. Together 
these studies suggest that it is feasible to ac -
curately gauge a person’s personality (as well 
as other personal characteristics, including 
highly private ones; Kosinski, Stillwell, & 
Graepel, 2013), merely based on digital so -
cial media behavior and without ever asking 
the person or anyone who knows the person. 
It does not take visionary imagination to re -alize both the scientific potential (e.g., for 
studying personality consequences, process -
es, and development) and the societal risks 
(e.g., “The Data That Turned the World Up -
side Down”; Grassegger & Krogerus, 2017) 
posed by this novel way of assessing person -
ality from daily online behavior.
In summary, once the Achilles’ heel of 
daily life research, the in vivo assessment 
of behavior is now rapidly progressing, fu -
eled by the immense advancements in mobile 
(e.g., smartphones, wearables) and online 
(e.g., social media, search engines) technolo -
gies. It is clear that we will see many more, 
maybe even groundbreaking, developments 
in this domain in the near to midrange fu -
ture. Given the double-  edged nature of the 
consequences of these developments, it is 
important that any technological progress 
be closely accompanied by efforts to under -
stand their societal impact, and to resolve 
central questions around personal privacy 
and data confidentiality, access, and own -
ership (de Montjoye et al., 2018; Pentland, 
2014).
Ecological Assessment of Daily Situations
The field of personality has recently made 
great progress in the conceptualization and 
measurement of situations as the third ele -
ment in the personality triad (Funder, 2016; 
Rauthmann et al., 2014). From the ecologi -
cal perspective highlighted in this chapter, it 
becomes important then not only to study 
experiences and behavior in vivo but to 
also assess situations directly in daily life 
(Wrzus & Mehl, 2017). As the momentary 
environment, situations are defined by ob -
jective cues, the observable elements such as 
objects, locations, people, and actions that 
surround a person at a given time, and by 
their “inner reflections,” the situation expe -
riences and perceptions that interpret and 
integrate the objective reality and imbue 
it with subjective meaning (Magnusson, 
1981; Rauthmann, Sherman, & Funder, 
2015; Wagerman & Funder, 2009). From a 
measurement perspective, the former calls 
primarily for a third-  person, observational 
and the latter primarily for a first-  person, 
self- report approach to real-world situation 
assessment.