Rodent Gambling Task. Results of the so-called Rodent Gambling Task are shown for different experimental groups as the preference index in 90 trials. Normal animals and animals subjected to mild stress developed a positive preference index whereas animals with inflammatory or neuropathic pain and animals with orbitofrontal cortex (OFC) lesions had a negative preference index. Preference Index is defined as in the Iowa Gambling Task (IGT, Bechara et al, 1994) as the number of low-risk choices minus the number of high-risk choices, divided by the number of completed trials. The index is calculated for each group of 10 consecutive trials. Solid lines, control groups; dotted lines, pain groups; narrow-spaced dashed lines, stress groups; wide-spaced dashed line, OFC lesion group. Original data presented in Pais-Vieira et al, 2007, 2008. Error bars are omitted for clarity.