Samuel Hewitt, PhD
samuelhewitt.bsky.social
Samuel Hewitt, PhD
@samuelhewitt.bsky.social
Machine Learning Engineer at Limbic
Building AI therapy
Previously, Max Planck Centre for Computational Psychiatry @ UCL
2 prompts attached !
April 10, 2025 at 12:15 PM
it wrote all the front-end code ! just need to connect your database and adjust the trials. I just gave it this image for the style
April 10, 2025 at 10:23 AM
Hey cognitive scientists

I asked lovable.dev to make me a 2-arm bandit RL task

2 prompts and 3 minutes later
🤯🤯🤯🤯

Play it:
preview--cosmic-bandit-quest.lovable.app

Think of the hours and grad student tears saved 😅

Yes lovable I accept your sponsorship terms
April 9, 2025 at 7:41 PM
Make a choice and get feedback
April 9, 2025 at 7:34 PM
Trial 1
April 9, 2025 at 7:34 PM
Hello world
April 9, 2025 at 7:34 PM
to my (limited) knowledge, this is the first study to show that fluctuations in how people feel predict subsequent changes in latent decision-making parameters
August 13, 2024 at 10:37 AM
motivation fluctuations predicted ⬆️willingness to make effort for reward

effect was
specific🎯(not for happiness, fatigue or sleep)
directional➡️(motivation changes lead to changes in decision-making parameters)
possibly clinically relevant🩺(stronger in high trait-apathy)
August 13, 2024 at 10:37 AM
we also validated a mobile effort-based choice task which captured effort discounting with high reliability (over 28 possible task pairs)
choices (mean = 0.78 ± 0.02, 95% CI [0.74, 0.82])
model parameters (e.g., reward sensitivity = 0.93, 95% CI [0.91, 0.95])
August 13, 2024 at 10:37 AM
we find that healthy adults (no conditions, no medication, age 18-45 [mean =32.4] yrs, 53% female) report substantial fluctuations in subjective motivation
linked with happiness, fatigue & sleep quality
trait-predict (day0) predicts⬇️mean & autocorrelation
August 13, 2024 at 10:37 AM
life is a complex tapestry of fluctuating feelings
Sometimes we feel motivated, often we don't!
we designed a study to ask (how) do such fluctuations influence choices? w/
@_BrainExplorer

N=155, days=15
3344 timepoints (845 tasks)
building on recent work
https://science.org/doi/10.1126/sciadv.adk
August 13, 2024 at 10:37 AM
why is that effortful task SO unappealing today?
v happy to share a BIG effort from my PhD!

Real-world fluctuations in motivation drive effort-based choices
https://osf.io/preprints/psyarxiv/w3x7d
with incredible co-authors Dr Agnes Norbury, Prof Quentin Huys & @tobiasuhauser.bsky.social
August 13, 2024 at 10:37 AM