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Failure to Obtain Instrumental Successive Negative Contrast in Tasks that Support Consummatory Successive Negative Contrast

  • Author(s): Sastre, Aristides
  • Lin, Jian-You
  • Reilly, Steve
  • et al.
Abstract

In four experiments (three in operant chambers, one in a runway) with food-deprived rats, we sought to obtain instrumental successive negative contrast (iSNC) and consummatory successive negative contrast (cSNC) following shifts in the value of liquid rewards. Despite finding robust cSNC in each of the four experiments, there was no indication of iSNC in any of the measured instrumental responses (pressing a lever, licking an empty spout, or time to traverse a runway). Consistent with the literature, these results might be taken to suggest that iSNC cannot be obtained following a downshift in liquid reward value. However, behaviors observed in the downshifted rats suggests that the absence of iSNC might be due to the occurrence of competing responses or nonoptimal test conditions. Thus, the failure to observe iSNC in rats that show cSNC is interpreted as a failure of performance.

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