Behavioral microanalyses refine sign-tracking characterization and uncover different response dynamics during omission and extinction learning
Lever counts looked the same, but video showed sign-tracking quietly survived under omission while it died in extinction.
01Research in Context
What this study did
Townsend et al. (2025) filmed rats during two extinction-like procedures. One group got omission: lever still appeared, but food only came if the rat did NOT touch it. The other group got plain extinction: lever appeared, no food ever.
The team counted both lever presses and tiny sign-tracking moves toward the lever. They wanted to see if the two procedures feel the same to the animal.
What they found
Total lever deflections dropped the same in both conditions. That made the procedures look identical.
Video told a different story. Under plain extinction, sign-tracking vanished. Under omission, the rats still leaned, approached, and sniffed the lever even though they rarely pressed it.
How this fits with other research
The finding extends Allan et al. (1991). They used a setback contingency that also cut sign-tracking, but they only counted key pecks. Townsend shows video would have revealed subtler moves.
It also updates Craig et al. (2018). Craig showed that off-baseline reinforcement history can weaken extinction resistance. Townsend adds that the form of behavior, not just its rate, can hide when you use omission instead of extinction.
Johnston et al. (2017) found rich alternative reinforcement causes bigger resurgence. Townsend’s omission is like a lean DRA; the covert sign-tracking they caught may be the early stage of that later resurgence.
Why it matters
If you only track button hits or vocal requests, you can miss covert resurgence under omission or DRA schedules. Run a quick video or momentary time-sample of approach, lean, or gaze before you declare problem behavior “extinguished.” When you switch from extinction to omission, plan extra probes and thinner thinning so hidden forms don’t bloom later.
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02At a glance
03Original abstract
Sign-tracking, a conditioned response in which animals engage with reward-predictive cues, is a powerful behavioral tool for assessing Pavlovian motivation. In rodents, it is most frequently studied via automatic readouts, such as deflections of levers that act as reward cues. These readouts have been immensely helpful, but they may not be ideal for some tasks and paradigms. For example, animals can show a range of sign-tracking responses to a lever cue that do not result in lever deflection, and a reduction in deflections when animals are exposed to an omission contingency (i.e., when lever deflection cancels reward) hides the fact that the animals are still sign-tracking in other ways. Here, we analyzed the behavior of sign-tracking animals through both video monitoring and automatic task readouts in Pavlovian conditioning. This analysis aided in the classification of sign-tracking animals and revealed that lever deflections do not result from any identifiable pattern of sign-tracking. We then used omission and extinction procedures to unmask detailed behavior changes that can only be detected with video data. Automated readouts showed similar reductions of lever deflection in both task conditions. However, detailed behavioral analysis revealed quite distinct behavioral adaptations to these conditions with sign-tracking decreasing entirely during extinction while many sign-tracking behaviors (biting, sniffing, etc.) seemed to remain persistent during omission despite the decrease in deflections. Detailed behavioral analysis was thus critical for capturing sign-tracking maintenance, persistence, and loss.
Learning & Memory, 2025 · doi:10.1101/lm.054065.124