Dissociating Task Acquisition from Expression During Learning Reveals Latent Knowledge

Abstract

Performance on cognitive tasks during learning is used to measure knowledge, yet it remains controversial since such testing is susceptible to contextual factors. To what extent does performance during learning depend on the testing context, rather than underlying knowledge? We trained mice, rats and ferrets on a range of tasks to examine how testing context impacts the acquisition of knowledge versus its expression. We interleaved reinforced trials with probe trials in which we omitted reinforcement. Across tasks, each animal species performed remarkably better in probe trials during learning and inter-animal variability was strikingly reduced. Reinforcement feedback is thus critical for learning-related behavioral improvements but, paradoxically masks the expression of underlying knowledge. We capture these results with a network model in which learning occurs during reinforced trials while context modulates only the read-out parameters. Probing learning by omitting reinforcement thus uncovers latent knowledge and identifies context-not "smartness"as the major source of individual variability.

A neural circuit architecture for rapid behavioral flexibility in goal-directed navigation

“…Thus, goal-oriented behavior can sometimes operate in two phases: first, a latent learning phase in which an animal explores and acquires an internal model of the structure of its environment, and second, a phase in which the animal modifies its behavior in that environment through its good or bad experiences in specific situations and/or places [10]. Many studies of learned behavior and its neural correlates, particularly those involving mammals, focus on the second phase, using trained animals that have already learned the basic structure of tasks and environments; in doing so, they study task performance more than task acquisition (but see, for example, [11][12][13][14][15]). By contrast, in many natural settings, animals must develop internal representations of their spatial relationship to their surroundings at the same time that they discover the environment's rules through reinforcement of specific actions or contexts.…”

Removal of reinforcement improves instrumental performance in humans by decreasing a general action bias rather than unmasking learnt associations

“…This increase in d ’ was driven by a more pronounced reduction of false alarm rate ( FAR ) than hit rate ( HR; ΔFAR - ΔHR = −0.07 ± 0.08, t 59 = −6.42, p <.001, Cohen’s d = −0.83). However, both measures decreased significantly in probe compared to pre-probe trials ( ΔHR = −0.08 ± 0.06, t 59 = −9.67, p <.001, Cohen’s d = −1.25; ΔFAR = −0.15 ± 0.08, t 59 = − 15.12, p <.001, Cohen’s d = −1.95, Fig 2C/D), while in (12) only a decrease in false alarm rate during probe trials was reported. Once reinforcement was reinstated, d ’ significantly decreased again ( Δd ’ = 0.15 ± 0.47, t 59 = 2.40, p =.020, Cohen’s d = 0.31, see Fig 7 in S1 Appendix).…”

“…Based on recent findings in rodents (12), we hypothesized that the performance of humans in an instrumental learning task increases during non-reinforced compared to reinforced periods. Therefore, we designed a visual go/no-go reinforcement learning task (Fig 1A ) consisting of reinforced trials which were interleaved with five probe blocks of non-reinforced trials.…”

“…These results contrast with a recent rodent study in the domain of associative learning: Omitting feedback during early learning improved performance. Notably, performance deteriorated again when reinforcement was reintroduced, suggesting that reinforcement masked the underlying knowledge acquired by the animals (12).…”

“…Specifically, we asked whether healthy volunteers’ performance benefits similarly from omitting reinforcement during instrumental learning. To this end, closely following Kuchibhotla and colleagues (12), we adopted a go/no-go task that required participants to learn, by trial and error, to respond to go stimuli to obtain reward and to withhold responding to no-go stimuli to avoid punishment (monetary wins and losses, respectively). Crucially, reinforced trials were interleaved with multiple blocks in which participants were instructed to continue responding as previously, but no reinforcement was delivered (probe blocks).…”