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FIGURE 8.19 Plasma corticosterone levels 15 minutes after the introduction of a balloon into
the cage of quails from lines selected for long or short duration of tonic immobility and for high
or low levels of social reinstatement behavior over 14 generations. ( ' ) Stressed, ( & ) control.
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HSR
LSR
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STI
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FIGURE 8.20 Plasma corticosterone levels after 15 minutes of social isolation in lines of
quails selected for long or short duration of tonic immobility and for high or low levels of social
reinstatement behavior over 14 generations. ( ' ) Stressed, ( & ) control.
to the long TI (high fear) line birds (6.4) which typically show tonic immo-
bility or freezing reactions. In the two selected lines and the control line,
restraint induced an increase in plasma corticosterone levels that was greater
in the short TI line compared to the control and long TI lines ( Figure 8.21 )
( Jones et al., 1994; Remingnon et al., 1996 ). The higher level of struggling
in the short TI (low fear) line was predictable. However, the relatively low
corticosterone response in the long TI (high fear) line was unexpected
 
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