・ Risk-sensitive human mate choice and impulsivity
・ Preference for Visual Variability in Lister-hooded Rats and European Starlings
Recent welfare studies across a wide range of captive animals indicate that
a certain level of variability in the captive environment has a positive
effect on welfare. In addition, there is a literature suggesting that
animals are motivated to seek information about changes in the environment
in order to reduce uncertainty. Here, we devised a simple experiment on
Lister-hooded rats and European starlings, looking at preference for visual
variability in the environment using a four-arm choice chamber. The visual
stimulus consisted of an 8x6 blue and yellow square checkerboard displayed
on a LCD monitor placed on the back wall of each choice chamber. Two of the
chambers showed constant visual stimuli, displaying static images of the
checkerboard display (C1) or its inverse (C2). The other two chambers showed
variable stimuli, switching between C1 and C2 either at a regular interval
or at a random interval with the mean of the regular interval. In separate
treatments, the duration of this interval was 'short' (0.5s), 'medium' (10s)
or 'long' (200s). Starlings, showed a significant difference in the time
spent in different choice chambers for the 'medium' and 'short' interval
treatments (F3,33=13.882, p<0.001; F3,33=35.05, p<0.001 respectively), but
not for the 'long' treatment (F3,33=0.26, p=0.856). Contrast estimates
showed a significant preference for random over regular switching intervals
and regular over constant intervals in 'medium' interval treatment.
Significant preferences in the 'short' interval treatment were in the
reverse order (constant>regular>random). In rats, no significant preference
was found in any of the treatments. Results for starlings show a preference
for variability in certain visual environments, and this is the first
experiment where an animal shows this type of preference without any
training or reinforcement. As rats have limited visual capabilities compared
to starlings, future studies may look for preference in olfactory
variability.
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