PETELLE MB, BLUMSTEIN DT: Can subjective personality ratings work? 1 UNCORRECTED PROOF A critical evaluation of subjective ratings: Unacquainted observers can reliably assess certain personality traits Matthew B. PETELLE 1 , Daniel T. BLUMSTEIN 1, 2 1 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095-1606, USA 2 Rocky Mountain Biological Laboratory, Crested Butte, CO 81224, USA Abstract Methods to measure consistent individual differences in behavior (i.e. animal personality) fall into two categories, subjective ratings and behavioral codings. Ratings are seldom used despite being potentially more efficient than codings. One potential limitation for the use of ratings is that it is assumed that long-term observers or experts in the field are required to score individuals. This can be problematic in many cases, especially for long-term ecological studies where there is high turnover in personnel. We tested whether raters who were unacquainted with subjects could produce reliable and valid personality assessments of yellow-bellied marmots Marmota flaviventris. Two raters, previously unacquainted with individuals and marmot behavior, scored 130 subjects on fifteen different adjectives in both open-field (OF) and mirror image stimulation (MIS) trials. Eight OF and nine MIS adjectives were reliable as indicated by both a high degree of intra-observer and inter-observer reliability. Additionally, some ratings were externally valid, correlating with behavioral codings. Our data suggest that activity/exploration and sociability can be a reliable and valid measurement of personality traits in studies where raters were unacquainted with subjects. These traits are observable with the personality tests we used; otherwise researchers using unacquainted raters should be cautious in the tests they employ [Current Zoology 60(2) : – , ]. Keywords Animal personality, Behavior codings, Marmots, Subjective ratings Animal personality (i.e., consistent individual differences in behavior) has been documented in numerous domestic and wild species (Gosling, 2001; Réale et al., 2007) and from invertebrates to vertebrates (Gosling, 2001; Hensley et al., 2012; Mather and Logue 2013). Behavioral codings and subjective ratings are two methods used to quantify personality (Gosling, 2001; Vazire et al., 2007). Both methods are applicable for use in the animals’ home environments or in behavioral tests, such as open-field and novel object tests. Behavioral codings measure the presence/absence, frequency, and/or duration of specific postures or behaviors, whereas subjective ratings use observers to score individuals based on a list of adjectives. In studies of non-human animals, codings are more commonly used because of their perceived objectivity and lack of human bias. Whereas ratings are used to a lesser extent, they are seen as a more holistic way to assess personality; additionally they are seen Received May 15, 2013; accepted Aug. 3, 2013.  Corresponding author. E-mail: mpetelle@ucla.edu © Current Zoology 2014