--- - |2 Resurgence is defined as the recurrence of a previously reinforced and then extinguished target response when reducing or eliminating a more recently reinforced alternative response. In experiments with children and pigeons, we evaluated patterns of resurgence across and within sessions through decreases in reinforcer availability by challenging alternative responding with extinction and progressive‐ratio schedules. In Phase 1, we reinforced only target responding. In Phase 2, we extinguished target responding while reinforcing an alternative response. Finally, Phase 3 assessed resurgence by (a) extinguishing alternative responding versus (b) introducing a progressive‐ratio schedule of reinforcement for alternative responding. In both children and pigeons, resurgence of target responding occurred in both conditions but generally was greater when assessed during extinction than with progressive ratios. Importantly, within‐session patterns of resurgence did not differ between testing with progressive ratios and extinction. Resurgence with progressive ratios tended to be greater with longer durations between reinforcers but we observed similar findings with only simulated reinforcers during extinction testing. Therefore, the present investigation reveals that the events contributing to instances of resurgence remain to be understood, and presents an approach from which to examine variables influencing within‐session patterns of resurgence. - Journal of the Experimental Analysis of Behavior, EarlyView.