tHE ‘HuAutLI ’ ALtERnAtIVE: AmARAntH AS REInFoRCER In oPERAnt PRoCEduRES

The progressive ratio (PR) schedule of reinforcement is widely used to assess rein-forcement strength. Rats typically complete higher ratio requirements for more pal-atable food. This effect is well characterized by the Mathematical Principles of Rein-forcement (MPR). In this experiment, either standard food pellets or amaranth grain were delivered according to PR schedules, with requirements increasing in steps of 1 (PR 1) or 3 (PR 3). Rats completed higher ratio requirements and displayed shorter pre-ratio pauses for pellets than for amaranth. Nevertheless, run-rates were similar across reinforcers. In terms of the theoretical parameters of MPR, similar values in a parameter (which indices incentive value) were obtained for amaranth and pellet reinforcers. This finding suggests that, although amaranth engenders less responding than pellets, amaranth grain is a reliable reinforcer for operant procedures. The MPR model accounted for the differences in quality of food. Key words: MPR model; progressive ratio schedules; food textures; amaranth; food pellets; rats