Biology Reference
In-Depth Information
Startle Tests
Startle tests mainly measure fear. In a startle test, an animal's reaction to a
sudden novel stimulus is used. Some examples of a sudden novel stimulus
are sudden opening of an umbrella, dropping a heavy chain, or a person
stamping his feet. The reaction of pigs to a person suddenly stamping his
foot was very effective for differentiating the behavior of different genetic
lines of pigs ( Lawrence et al., 1991 ). Startle tests are most appropriate for
“one-time” temperament tests. Animals are likely to habituate quickly to
repeated exposure to sudden novel stimulus.
Tests that Measure Separation Distress, Fear, and Seeking
Isolation Tests
Isolation tests measure PANIC (separation distress). In a typical isolation
study, animals are separated from herd mates and placed alone in a pen.
Vocalization and locomotor agitation is scored. In sheep, Basile et al.
(2009); Lansade et al. (2008) ; Ligour et al. (2011) ; found that vocalization
(bleats) was not correlated with a tendency to avoid or approach people.
Isolating single sheep in an arena may be measuring two different emotional
systems. The vocalization was probably measuring PANIC (separation dis-
tress) and the tendency to either approach or avoid people may be due to
FEAR. In a heritability study of emotional reactivity, Boissy et al. (2005)
exposed lambs to three challenging tests involving novelty, human contact,
and social isolation. The highest heritability was for high bleats (h2
0.48)
during social isolation. In horses, the frequency of vocalization (neighing)
during isolation was stable over time ( Lansade et al., 2008 ). The research
also measured attraction towards other horses (gregariousness) and con-
cluded that the trait of gregariousness is stable over a series of tests from 8
months to 2.5 years ( Lansade et al., 2008 ). Possibly gregariousness and
PANIC (separation distress) are separate but linked traits.
5
Open Field Tests
Open field tests may elicit a mix of emotional system responses: FEAR
(a strong emotion caused by anticipation or awareness or danger), but may
also measure SEEK (intensively energized to explore) and PANIC (separa-
tion distress). In an open-field test, an animal is placed in an arena and its
activity or the distance it walks is measured. Beausoleil et al. (2008) tested
Merino sheep bred for either low or high activity in an open field. With a
stationary person standing inside the arena, the more active genetic line
walked around more, vocalized (bleated) more, and spent more time closely
investigating the person in the arena. Analysis showed two emotional sys-
tems affecting behavior of the more active genetic line. The active genetic
line was less fearful and more exploratory compared to the less active line.
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