Behavioral Genetics and Animal Science - Genetics and the Behavior of Domestic Animals - page 22

individual animal's fear response. Rogan and LeDoux (1996) suggest that fear
is the product of a neural system that evolved to detect danger and causes an
animal to make a response to protect itself. Plomin and Daniels (1987) found a
substantial genetic influence on shyness (fearfulness) in human children. Shy
behavior in novel situations is considered a stable psychological characteristic
of certain individuals. Shyness is also suggested to be among the most
heritable dimensions of human temperament throughout the life-span.
In an experiment designed to control for maternal effects on temperament
and emotionality, Broadhurst (1960) conducted cross-fostering experiments
on Maudsley Reactive (MR) and Non-Reactive (MNR) rats. These lines of
rats are genetically selected for high or low levels of emotional reactivity.
The results showed that maternal effects were not great enough to
completely mask the temperament differences between the two lines
( Broadhurst, 1960 ; Eysenck and Broadhurst, 1964 ). Maternal effects can
affect temperament, but they are not great enough to completely change the
temperament of a cross-fostered animal which has a temperament very dif-
ferent from that of the foster mother. In an extensive review of the literature,
Broadhurst (1975) examined the role of heredity in the formation
of behavior and found that differences in temperament between rats persist
when the animals are all raised in the same environment.
In their study of genetic effects on dog behavior in a large sample, Fuller
and Thompson (1978) found that “simply providing the same defined con-
trolled environment for each genetic group is not enough. Conditions must
not only be uniform for all groups, but also favorable to the development
of the behavior of interest.” In wartime Russia, Krushinski (1960) investi-
gated the ability of dogs to be trained for the antitank service or as trail dogs
trained to track human scent. The dogs were tied to a spike driven into the
ground and the person who regularly looked after them let them lick from
a bowl of food for a few moments then summoned the dog to follow the man
as he moved 10

15 meters away. Activity of each dog was measured with a
pedometer for the next 2 minutes. The most active dogs were found to be the
best antitank dogs. They were also fearless. In the antitank service, dogs were
trained to run up to a tank and either run alongside of it or penetrate under
the caterpillars of the tank. In order to do this, the dogs had to overcome their
natural fear of a tank moving toward them at high speed. The less active dogs
(as measured by the pedometer) were found to make the best trailer dogs.
They slowly followed a trail and kept their noses carefully to the scent while
negotiating the corners and turns on the trail. The more active dogs trailed at
too high a speed and often jumped the corners and turns in the trail, which
sometimes resulted in switching to another trail.
Mahut (1958) demonstrated an example of differences in fear responses
between beagles and terriers. When frightened, beagles freeze and terriers
run around frantically. In domestic livestock, measuring fear reactions during
restraint or in an open field test reveals differences in temperament both