Cognitive performance
In the observer trials, 55 of 60 pairs established clear
dominant/subordinate relationships within the five-hour period.
Considering time differences between observer and naïve trials
(i.e. observer trial time minus naïve trial time), trout raised
in complex habitats showed greater improvement in time needed to
establish a stable hierarchy in the observer trial than did those from
simple habitats (F 1,98 = 13.09,p < 0.001). Females generally showed less improvement
than did males in the observer trials over the naïve trials
(F 1,98 = 4.57, p = 0.034), especially
those from the simple habitat; but, females from the complex habitat
showed greater improvement than did males (sex/habitat interaction:F 1,98 = 11.41, p = 0.001) (Fig. 5A).
Greater brain mass was also associated with quicker times in the
observer trial (F 1,42 = 6.93, p = 0.011)
(Fig. 5B), but no specific brain region exerted a significant effect on
time differences between trials (telencephalon:F 1,42 = 1.87, p = 0.179; optic tectum:F 1,42 = 0.24, p = 0.627; cerebellum:F 1,42 = 0.05, p = 0.828; olfactory bulb:F 1,42 = 0.88, p = 0.353).