 2. History, Measurement, and Conceptual Elaboration of the Big‑Five Trait Taxonomy  49
tor as social adaptability, likability, friendly 
compliance, agreeableness, and love. Of 
course, some variation across studies is to 
be expected with dimensions as broad and 
inclusive as the Big Five, because researchers 
differ in the variables they include, thus rep -
resenting different parts of the factor’s total 
range of meaning. Moreover, researchers 
differ in their preferences for factor labels 
even when the factor content is quite similar. 
The fact that the labels differ does not nec -
essarily mean that the factors are different, 
too. Thus, there may be more commonality 
than meets the eye.
John (1990) proposed a prototype ap -
proach to identify these commonalities 
across studies. Natural categories such as 
the Big Five typically have fuzzy and par -
tially overlapping definitions (Rosch, 1978), 
but they can still be extremely useful when 
defined in terms of prototypical exemplars. 
Similarly, the Big Five may be defined with 
prototypical traits that occur consistently 
across studies. One way to integrate the 
various interpretations of the factors is to 
conceptually map the five dimensions into 
a common language. To abstract the com -
mon elements in these findings, John (1989, 
1990) used human judges, and the 300 
terms included in the Adjective Check List 
(ACL; Gough & Heilbrun, 1983) served as 
the standard language.
Conceptually Derived Prototype 
Descriptions of the Big Five 
and their Validation in Observer Data
A set of 10 judges first developed a detailed 
understanding of the Big Five by reviewing 
the factor solutions and interpretations of all 
major Big Five articles published by 1988. 
The judges then independently sorted each 
of the 300 items in the ACL into one of the 
Big-Five domains or into a sixth “other” 
category, with substantial interjudge agree -
ment. In all, 112 of the 300 ACL terms were 
assigned to one of the Big Five, with 90% or 
better agreement. These terms form a rela -
tively narrow, or “core,” definition of the 
five factors, because they include only those 
traits that appeared consistently across stud -
ies. As with any rationally constructed mea -
sure, the validity of these categorizations was tested empirically in a factor analysis of the 
112 terms. Whereas most Big Five research 
has been based on college students’ self- and 
peer ratings, this study used observer data 
obtained from psychologists. John (1990) 
used a sample of 140 men and 140 women 
who had participated in groups of 10–15 in 
one of the assessment weekends the Institute 
of Personality and Social Research (IPSR, 
formerly the Institute for Personality Assess -
ment Research [IPAR]) at Berkeley. As each 
subject had been described on the ACL by 
10 staff members, a factor analysis could be 
performed on more reliable, aggregated ob -
server judgments. The varimax rotation fac -
tor loadings, shown in Table 2.4, provide a 
compelling confirmation of the initial proto -
types. All but one item loaded on its hypoth -
esized factor in the expected direction, and 
most of the loadings were substantial.
Note that the items defining each of the 
factors cover a broad range of content. For 
example, Factor I includes traits such as 
active, adventurous, assertive, dominant, 
energetic, enthusiastic, outgoing, sociable,  
and show-off . In light of this substantial 
bandwidth, the heterogeneity of the previ -
ous factor labels is understood more eas -
ily: Different investigators have focused on 
different components, or facets, of the total 
range of meaning subsumed by each fac -
tor. In this study, the Extraversion factor 
includes at least three major distinguishable 
components: sociability (outgoing, sociable, 
talkative, noisy), assertiveness (assertive, 
forceful, outspoken, bossy), and energy level 
(active, energetic, enthusiastic, and spunky). 
Note that these three components are simi -
lar to several of the facets Costa and Mc -
Crae (1992) included in their definition of 
the Extraversion domain—  gregariousness, 
assertiveness, and positive emotions/activity 
(see Table 2.3)—and these three have also 
been identified in a lexical study that empiri -
cally identified facets across two languages 
(Saucier & Ostendorf, 1999), as shown in 
Table 2.3. The traits that define the Consci -
entiousness factor in Table 2.4 seem to cap -
ture three major themes, namely Organiza -
tion or Orderliness (thorough, precise, and 
painstaking vs. disorderly), Productivity (ef -
ficient, planful, and deliberate vs. frivolous), 
and Responsibility (responsible, reliable, and 
dependable vs. irresponsible). More gener -