Isopods are cold blooded, which means their bodies take on the temperature of their surroundings. Place 4-6 isopods in a small jar with a cover and float it on water in a pan. Add ice cubes and a thermometer and stir gently so as not to tip the jar. The isopods will speed up their movements as the temperature rises. Re move the Isopods at this time or they will go into heat stupor which may kill them if prolonged.
Isopods also react to light.
You might devise your own tests using different degrees of light or colored fiIters and test their responses.