How Studying Interactions Between Animal Emotions, Cognition, and Personality Can Contribute to Improve Farm - Genetics and the Behavior of Domestic Animals - page 94

Personality as a Complex Intermediate Variable
As suggested throughout this chapter, behavioral reactions and physiological
patterns observed in animals under emotional challenges are only indicators
of fear/anxiety and cannot be considered as direct measures of a fear/anxiety
state. Fear must be evaluated by studying not only the intensity of a unique
response but also the overall strategy. The different mechanisms underlying
fear-related responses probably depend on other motivational systems which
may modulate these responses. The strength of reaction in response to a
stressor is often used to assess the strength of the underlying emotion. The
classic example is the fight/flight response that assumes that a higher level
of activity indicates a higher level of fear. However, an absence of activity,
immobility, also indicates fear. This might explain the negative correlation
between activity while confined and in social isolation and the fear of
humans in sheep ( Beausoleil et al., 2008 ). The interaction of several person-
ality traits, such as fearfulness, activity and coping strategies (active/passive)
can explain these complex results ( Erhard et al., 1999; Koolhaas et al., 1999;
van Reenen et al., 2005 ).
Vocalizations are often considered to be an indicator of fear: the more an
animal vocalizes, the more stressed it probably is. Vocalizations, however,
are also a means of communication, and could be an indicator of sociability.
Because of the complexity of the phenomena that can affect emotional
behavior, it is not possible to just consider the results isolated from their
context. A measurement used as a fear indicator in one situation cannot be
directly extrapolated to others, and it is impossible to simply assess the mag-
nitude of concepts like fear and anxiety on the basis of a single “objective
and perfect measurement.”

Pre-existing Characteristics of Temperament
Genetic Background and Genetic Models of Emotional Reactivity
Although farm animals have been domesticated over many centuries, fear-
related behaviors still vary considerably both within and between populations
( Boissy et al., 2005b; Hemsworth, 2003 ). An animal's genetic background plays
a major role in determining its fear levels and its ability to adapt to environmen-
tal changes and challenges. Large differences in emotional reactivity are also
apparent within and between farm animal breeds ( Boissy and Bouissou, 1995 ;
Boissy et al., 2005a; Faure et al., 2003 ). The approaches go from comparison of
breeds ( Hansen et al.,2001 ) to estimation of genetic correlations and heritability
within the same breed ( Benhajali et al., 2010 ), selection lines (mink: Malmkvist
and Hansen, 2002 ; sheep: Beausoleil et al., 2008, 2012 ) and the study of quanti-
tative trait loci (QTL) ( Guti´rrez-Gil et al., 2008; Hazard et al., 2012; Jensen
et al.,2008 ). Estimates of heritability of

fear in domestic animals seem