Participants in study 2 were instructed to not eat after their standardised dinner in both sleep conditions. Ghrelin was increased by both hunger and sleep deprivation in this study.

Those are great questions. I agree that the inclusion of acyl ghrelin would strengthen our claims. However, we did not have acyl ghrelin data for both studies, so to allow for the comparison we focused on des-acyl ghrelin.

More details are in the preprint ( doi.org/10.1101/2025... )
Let me know if you have any questions

Our results suggest that state-dependent influences, via ghrelin in particular, on risky decision-making are weaker than previously thought.

When looking at the neural activity, we found again no effect of ghrelin. Not for subjective value (figure) or choices.

We compared several computational models to understand the underlying processes. It is possible that the same behaviour comes from different parameter values. We found that the prospect theory provided the best fit to the data and that none of its parameters differed between conditions.

This is not what we found. While we saw that our manipulations increased ghrelin levels, we did not see an increase in risky choices in either study.

In study 2, another group of participants did the same. However, they did it after one night of normal sleep (NNS) and after one night of total sleep deprivation (TSD). Both manipulations increase the ghrelin levels so we expected increased risk taking in the fasting condition and the TSD condition.

We set out to investigate this effect with two separate studies. Participants had to choose between €20 guaranteed or a larger amount with a smaller reward probability. In study 1 they did this while sated (SAT) and after a short fasting period (FAS).

Blood levels of ghrelin increase when people get hungry. And due to its interaction with the dopaminergic reward system, it is a prime candidate to explain why we become more risk-seeking when lacking food.

Previous studies found that people make more risky decisions when they are hungry or sleep deprived. One of the suspects behind this effect is “the hunger hormone” ghrelin.

Congrats on the new work, it looks great! (I think the repo is still private because I get a 404 when I try to open it)

A short summary of the study is here:
2025.ccneuro.org/poster/?id=j...
The actual paper should follow soon.
🧠📈🧠💻

I used RL for my Master thesis and the scripts are all available github.com/StevenGeysen.... They are not a great example for organization though. For that I have since then learned to use the data science cookiecutter cookiecutter-data-science.drivendata.org