Stefano Palminteri
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stepalminteri.bsky.social
Stefano Palminteri
@stepalminteri.bsky.social
Computational cognitive scientist interested in learning and decision-making in human and machiches
Research director of the Human Reinforcement Learning team
Ecole Normale Supérieure (ENS)
Institut National de la Santé et Recherche Médicale (INSERM)
I think this is what we would have observed in Germain's and Constance's paper respectively if decay were true
October 20, 2025 at 3:37 PM
Thanks for the pointer Vinny!
October 19, 2025 at 10:19 AM
Exhibit #3: back to "stable" tasks, @constancedestais.bsky.social conditioned learning rates on confidence over time, and show that the asymmetry is still there. Indeed, it increases over time. Note that the model structure would have perfectly allowed for a "symmetric decaying" pattern 4/n
October 19, 2025 at 8:22 AM
Exhibit #2: learning rate bias has been reported (by us and other groups) in volatile tasks or conditions where, normatively, learning rates should not decay, and, perhaps more importantly, empirically, they indeed do not decay - if not, accuracy would not be above chance 3/n
doi.org/10.1016/j.ti...
October 19, 2025 at 8:22 AM
Exhibit #1: I was aware of this possibility since our first paper on the topic, and this is why we fitted separate learning rates in the first half and the second half of the learning phase. We found no evidence of decay and robust bias in both phases 2/n

www.nature.com/articles/s41...
October 19, 2025 at 8:22 AM
2/2 this is the second paper by Vidal and Moran.

osf.io/preprints/ps...
OSF
osf.io
October 14, 2025 at 1:24 PM
Something similar has been going on concerning learning bias versus perseveration. Initially fuelled by Kentaro Katahira and co, and more recently by Juan Vidal and Rani Moran. (see the discussion, about what counts as a plausible computation)
See this 1/2 and...
psycnet.apa.org/buy/2023-182...
APA PsycNet
psycnet.apa.org
October 14, 2025 at 1:24 PM
I think that is where I disagree with the author. Asymmetry is apparent, only if we assume people are Bayesian (which I do not believe is the case). But then I like that a "rational" analysis (Bays) of the task leads to the emergence of asymmetry, which may explains why the it is used by the brain
October 14, 2025 at 9:27 AM
I guess the missing link here is "However, we find that even if the agent updates its belief via, arguably objective, Bayesian inference, fitting the above model demonstrates both the biases". I working under the assumption that the Bayes solution is understood as normative given the task here
October 14, 2025 at 8:00 AM
I am very humbled that during the past years so many smart people took seriously our research questions and results to push forward our understanding.
On the specific subject matter (bias or optimal) I am still persuaded that it is a bias, that just happens to be generally optimal 😉
October 13, 2025 at 12:03 PM
Also quite coherent with what has been found by @akjagadish.bsky.social and co that asymmetric update emerges as an optimal solution in a neural-network meta-reinforcement learning agent arxiv.org/abs/2402.03969
In-context learning agents are asymmetric belief updaters
We study the in-context learning dynamics of large language models (LLMs) using three instrumental learning tasks adapted from cognitive psychology. We find that LLMs update their beliefs in an asymme...
arxiv.org
October 13, 2025 at 12:03 PM
It resonates perfectly well with what we (with @isabellehoxha.bsky.social and Léo Sperber) have shown, that the bias emerges as an evolutionary stable solution in multi-agent simulations

www.pnas.org/doi/abs/10.1...
PNAS
Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans...
www.pnas.org
October 13, 2025 at 12:03 PM