The present study compares behavioral changes between two distinct rodent groups, hamsters (Mesocricetus auratus) and Wistar rats, when submitted in the same homogeneous experimental situations to a serial conditional discrimination procedure which involves water deprivation and the processing of temporal variables. Both hamsters and rats acquired serial positive conditional discrimination as indicated by higher frequencies of magazine-oriented behavior during the tone followed by reinforcement (T+) and preceded by the feature stimulus light (L) and during the empty interval, than during the tone alone not followed by reinforcement (T-). Rats' frequencies of magazine-oriented behavior were high during T+ and T-, initially during training, and decreased during T-as the training progressed. However, the hamsters' frequencies of magazine-oriented behavior started very low and increased only during T+ as the training progressed. Comparison of the frequencies of magazine-oriented behavior during the empty interval in relation to the frequencies during the preceding L period showed that rats' frequencies remained very high and hamsters' frequencies increased during training. These results suggest that rats and hamsters have different behavioral strategies for the acquisition of a conditional discrimination. The results of the comparisons made in these experiments support the view of the importance of an ecological psychology approach to the understanding of complex learning in animals. Correspondence

Highly additized low viscous lubricants, new coatings, and surface treatments have been employed by original equipment manufacturers in several tribosystems to reduce emission and fuel consumption. In this sense, this work investigates the tribological response of four different advanced fully formulated gear oils and three different materials (coatings and topography) in terms of friction and wear using a ball-on-disc test rig under pure unidirectional sliding condition and boundary lubrication. The tested lubricants had different base oils: mineral, semi-synthetic, and synthetic with different additive packages. The ball's material was AISI 52100 bearing steel and the bulk material of the tested specimens (discs) were SAE 4320 steel with surface as follows: (i) ground; (ii) subjected to ceramic shot peening (CSP) and, (iii) coated with WC/C. Optical and scanning electron microscopy and 3D profilometry were used to evaluate the wear track and tribofilm formation. It was found that the frictional dependence on the surface topography and lubricant type is not significant, whilst the wear mechanisms were highly dependent on material and surface conditioning. The harder and rougher the contact body, the higher the wear produced in the counter body. At the harsher conditions base oil type control wear more effectively than the additive package.