Table 4.
Means and standard deviations (in parentheses) of group mean parameters with the VPP model.
| VPP parameters | HC | A | H |
|---|---|---|---|
| Learning rate (A) | 0.010 (0.008) | 0.019 (0.011) | 0.070 (0.044) |
| Reward sensitivity (α) | 0.518 (0.149) | 0.374 (0.137) | 0.481 (0.159) |
| Response sensitivity (c) | 2.017 (0.419) | 1.894 (0.329) | 1.368 (0.125) |
| Loss aversion (λ)a | 0.717 (0.273) | 0.593 (0.275) | 0.023 (0.033) |
| Perseverance after gain (εp) | −0.001 (0.154) | −0.181 (0.179) | 0.050 (0.204) |
| Perseverance after loss (εn) | −0.726 (0.296) | −0.500 (0.297) | −0.249 (0.192) |
| Perseverance decay rate (k) | 0.481 (0.062) | 0.404 (0.067) | 0.337 (0.073) |
| RL weight (ω) | 0.825 (0.110) | 0.714 (0.183) | 0.677 (0.078) |
HC, healthy controls; A, amphetamine; H, heroin.
a
HC, A > H.