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Languages: Matlab and R

Claire Smid, 20 November 2019

UPDATE: Claire Smid, 24 August 2020 : added more general information

UPDATE: Claire Smid, 17 September 2020 : added k-fold information

UPDATE: Claire Smid, 8 April 2021 : added parameter recovery information and folders

UPDATE: Claire Smid, 6 July 2021 : we now use gamma, beta and normal priors in the model-fitting, as opposed to using uniform priors previously. In addition, rewards were entered as their absolute value of points (0-9) rather than scaled down to be between 0 and 1 as was done previously. This was mainly done to improve the reliability of recovering the parameters in the model, and to avoid pooling at the bounds as we saw in earlier versions.

This is the main folder to replicate the computational modelling executed in the model-based/model-free developmental publication. Preprint on PsychArxiv: https://psyarxiv.com/ervsb/ by Claire Smid, Wouter Kool, Tobias Hauser and Nikolaus Steinbeis.

This code is mainly based on the code provided by Wouter Kool, e.g. Kool et al. 2016: https://github.com/wkool/tradeoffs, Kool et al. 2017: https://github.com/wkool/arbitration

Follow the steps below to recreate the analysis as reported. For any questions, please email to: claire.smid.17@ucl.ac.uk or claire.r.smid@gmail.com

Task

The current task was based on the format from Kool et al. 2016 and Kool et al. 2017. Stimuli for this task has been developed and shared previously by the authors of 'From Creatures of Habit to goal-directed learners' by Decker et al. 2016: https://pubmed.ncbi.nlm.nih.gov/27084852/

Data

The data for the 114 children and 24 adults is included in the 'data' folder. After exclusion criteria as described in our paper, we were left with 85 children.

Analysis

Step 1. Combining data files.

Run the script 'Step1_combine_group_data.m' to create two combined data files for the children and adult data. The resulting data files will be 'adultgroupdata.mat' and 'kidgroupdata.mat' and will be saved in the current folder. The function will also output two log files, named 'kidlog.mat' and 'adultlog.mat'. These two files will record how many missed trials there were per participant and how many trials available in total, and keep a record of which participants were excluded (following the guidelines as specified in the paper. The outputted data files will be used for following analysis but will not be changed by them. The 'mfit-master' folder contains the optimization functions. The folder named 'data' contains the raw data from all subjects.

Step 2. Parameter recovery for the 6-parameter and 7-parameter model

In the folder 'Parameter_Recovery' there are scripts to run parameter recovery for both the 6- and 7-parameter model for the task included in this paper. The task in this paper is different from previous versions (Kool et al 2016, Kool et al 2017), since the trial duration is shorter (original had 200, this one has 140). The scripts 'Main_Parameter_Recovery_6Params.m' and 'Main_Parameter_Recovery_7Params.m' can be used to run the parameter recovery for 200 agents, for 200, 140 or 100 trials.

Those two main scripts further use the scripts:

  • set_simulation_params6.m # - defines the parameter bounds and Gamma, beta and Normal priors used for the 6 parameter model
  • set_simulation_params7.m # - defines the parameter bounds and Gamma, beta and Normal priors used for the 7 parameter model
  • MBMF_generate_sim_6Params.m # - generates simulated behaviour for the 6 parameter model
  • MBMF_generate_sim_7Params.m # - generates simulated behaviour for the 7 parameter model
  • MB_MF_llik_simulation_6Params.m # - estimates the parameters for the 6 parameter model
  • MB_MF_llik_simulation_7Params.m # - estimates the parameters for the 7 parameter model

and the model fitting tools included in the 'mfit-master' folder. The model fitting tools in the mfit-master folder, and especially the 'mfit-optimize.m' script written by Sam Gershmann, have not been edited except for inlcuding the number of nstarts (random starting locations for optimizer), trials and participant ID in the output (these extra lines are commented in). the mfit toolbox: https://github.com/sjgershm/mfit

Step 3. Fitting the 6 parameter RL model (from Kool et al 2016) and creating model-free simulations

The folder 'RL_6ParamsModel_and_Sims' contains the scripts to fit the 6-parameter reinforcement learning model to the behavioural data of the children and the adults. By running the script 'Main_wrapper_6Params.m', the model will be fitted to both participant groups. The 6-parameter model is agnostic for the stakes, so it can be fit to all trials (rather than having two w-parameters split across low and high stake trials). It therefore provides as baseline model-based decision-making measure across all trials.

The Model-free simulations can be created by going into the 'model_free_simulations' folder with the 'Main_MF_Sims.m' script. In the script, we take the parameters from the children as outputted by the 6-parameter model, add noise to them, set w to 0, then simulate behaviour with this, and then take the outputted parameters of this to again simulate behaviour, setting the w-parameter to 0.

We then repeat this for 500 iterations of the total sample of 85 children, giving us a total of 42500 simulations that have been simulated and fitted twice. We then take the grand mean of the w-parameter of these 500 means as the true-model-free value of w. The 'CLUSTER_Main_MF_Sims.m' script is adapted to be run on a computing cluster. We needed to break the simulations into ~10 sections that were run separately and later combined. The 'Get_MF_Sims_its_means.m' script combines the files from different iterations.

Step 4. Running the 7 parameter RL model (from Kool et al 2017) 

The folder 'RL_7ParamsModel_and_Sims' contains the scripts to fit the 7-parameter reinforcement learning model to the behavioural data of the children and the adults. By running the script 'Main_wrapper_7Params.m', the model will be fitted to both participant groups. The 7-parameter model includes two w-parameters that differ across low and high stake trials, allowing investigation of whether the degree of model-based decision-making differs per stake.

Step 5. Regression-based model-free / model-based measures (based on Kool et al. 2016)

The 'Stay_Probabilities' folder has the scripts that generate choice probabilities on a trial basis, for both children and adults and the 6- and 7-parameter models that can be used in further regression analysis. In order to have a more 'behavioural' approach, we used the raw data from the participants, e.g. their actual rewards received, the similarity of starting state and whether they repeated a choice to a planet (staying) or not.

For the article, the regression analysis was conducted in R using the lme4 package. Candidate models were compared via nested model selection with the AICcmodavg package in R.

Step 6. k-fold Cross Validation

In the 'k-fold_Cross_Validation' folder, scripts are included to check how well both models performed. The script containing 'CLUSTER' in the title is adapted to be run on a computing cluster.

Step 7. Analyses with R

In the 'R_scripts' folder, the R scripts used to recreate the main analyses of the paper are included. the 'GLM_model_selection' script includes the generalised linear model analysis for the stay probabilities, and the model selection used to find the winning model for both children and adults.

The 'All_plots' script contains the code to recreate the main plots used in the paper.

References

Decker, J. H., Otto, A. R., Daw, N. D., & Hartley, C. A. (2016). From creatures of habit to goal-directed learners: Tracking the developmental emergence of model-based reinforcement learning. Psychological science, 27(6), 848-858.

Kool, W., Cushman, F. A., & Gershman, S. J. (2016). When does model-based control pay off?. PLoS computational biology, 12(8), e1005090.

Kool, W., Gershman, S. J., & Cushman, F. A. (2017). Cost-benefit arbitration between multiple reinforcement-learning systems. Psychological science, 28(9), 1321-1333.

About

Scripts, data and tasks for running the analyses as described in https://psyarxiv.com/ervsb/

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