Lab Research


Relative reward effects..what are they?  They are basically one form of outcome comparison.  Economists would call it commodity-choice (Kagel et al., 1995) and talk about commodity sets being compared and substituted based on marginal value.  We talk about outcome(s) and develop the research based on motivational theory (approach-approach; approach-avoid; avoid-avoid) as a way to describe outcome valence and inspect outcome disparity effects. Outcome relativity is apparent in behavior or motivation...where is it in the brain?  Our team addresses this issue.


These effects (time-dependent delay discounting) or relative outcome comparisons are dynamic alterations in neural representations.  We are exploring these representations- where they are and their neurophysiological basis in the brain.  the striatum is a hotspot for these activations and the figure from our 2016 eNeuro paper shows the power of relativity at the neural level. 

  We use different behavioral paradigms to examine how reward information guides action and decision-making.  Some of the work focuses on rapid. dynamic changes and other work examines long-term interactions that depend upon components of choice such as discrimination, preference and relative valuation of outcomes.


Recent work on the topic

Striatal Activity and Reward Relativity: Neural Signals Encoding Dynamic Outcome Valuation.Webber ES, Mankin DE, Cromwell HC. eNeuro. 2016 Nov 1;3(5). pii: ENEURO.0022-16.2016. 

Effects of striatal lesions on components of choice: Reward discrimination, preference, and relative valuation.Ricker JM, Kopchock RJ 3rd, Drown RM, Cromwell HC. Behav Brain Res. 2016 Dec 15;315:130-40. doi: 10.1016/j.bbr.2016.08.031

Fractionating choice: A study on reward discrimination, preference, and relative valuation in the rat (Rattus norvegicus).Ricker JM, Hatch JD, Powers DD, Cromwell HC. J Comp Psychol. 2016 May;130(2):174-86. doi: 10.1037/com0000034. Epub 2016 Apr 14.

Relative reward effects on operant behavior: Incentive contrast, induction and variety effects.Webber ES, Chambers NE, Kostek JA, Mankin DE, Cromwell HC. Behav Processes. 2015 Jul;116:87-99. doi: 10.1016/j.beproc.2015.05.003. Epub 2015 May 12

Emotion and relative reward processing: an investigation on instrumental successive negative contrast and ultrasonic vocalizations in the rat.Binkley KA, Webber ES, Powers DD, Cromwell HC.Behav Processes. 2014 Sep;107:167-74. doi: 10.1016/j.beproc.2014.07.011. Epub 2014 Aug 20

Relative reward processing in primate striatum.Cromwell HC, Hassani OK, Schultz W.Exp Brain Res. 2005 May;162(4):520-5. Epub 2005 Mar 8

RELATIVE REWARD EFFECTS.   This is a long running interest of the lab's and one of the fundamental properties of motivational behavior.  The capacity to retain elements of one outcome for comparison to other outcomes creates minor to massive shifts in behavioral strategies related to those outcomes.  The effect is known as reward contrast, incentive contrast and equity aversion and it has been examined as a powerful behavioral influence in bees to humans to baboons to rats.  All organisms compare constantly.  What remains to be answered is how the brain integrates this information, why specific information is stored and how emotions can play such a large role in this effect (frustration, anger and pleasure).  Our previous work found the neural correlates for the relative reward process in the striatum of behaving monkeys.  Our current work explores this issue in greater detail with work on the neural topology and the neural computations that underlie how an organism decided it has been cheated or basks in the glow of a most preferred reward so much better after the experience of the dreaded last place outcome recently exposed to.



Dan Powers operating the dual-choice environmental set-up. The apparatus enables accurate examination of decision making in the rodent and reveals preferences-both stable and changing!