Rats (Rattus norvegicus) find occupancy of a restraint tube rewarding.

Two experiments evaluated whether rats' occupancy of a restraint tube is reinforcing. In Experiment 1, each rat in the 0-min group moved freely in a chamber where a wall blocked access to a restraint tube. After 10 min the wall was removed, permitting 15 min of chamber access and tube entry.

Does a rat free a trapped rat due to empathy or for sociality?

This report evaluates whether a rat releasing a trapped rat from a restraint tube is better explained as due to its empathic motivation or to the pursuit of social contact. In the first condition, each of six rats chose in an E maze between entering an empty goal box versus entering a goal box where its entrance caused a rat trapped in a restraint tube to be released. Rats preferred the goal box with the trapped rat over the empty goal box.

Odor-Cued Bitter Taste Avoidance.

In the course of our ongoing studies of odor-cued taste avoidance (OCTA) to measure olfactory capabilities in animals, we observed that mice could rapidly learn to use the vapor of the classical bitterant quinine hydrochloride to avoid contact with the tastant. Here we expand on this observation to determine which among several compounds generally classed as bitter could be detected at a distance. Since mice were initially naïve we were able to assess whether the vapors of the bitter compounds tested were innately aversive as are their tastes.

Does a rat release a soaked conspecific due to empathy?

In Experiment 1, rats choosing in an E maze preferred to release a rat standing in a pool of water to dry ground over a rat already standing on dry ground. Five additional experiments showed that the choosing rat's preference for releasing the wet rat was maintained by two separable outcomes: (1) the social contact offered by the released rat and (2) the reinforcing value of proximity to a pool of water. These results call into question Sato et al.