Anxiety-Like Behavioural Inhibition Is Normative under Environmental Threat-Reward Correlations
Fig 3
Human approach-avoidance conflict model.
A: In experiments 1, 2 and 4, a human player (green triangle) rests in a safe place on a 2×2 grid, opposite a “sleeping predator”(grey circle). On each epoch, 6 successive reward tokens appear on the remaining two grid blocks at random time points. Once they have appeared on the grid, the time until they disappear is exponentially distributed. The player can press a key (experiments 1–2) or move a joystick (experiment 4) to collect these tokens which accumulate over any given epoch. At any time during the game, the predator becomes active with constant probability, but once active it will only reveal itself if the player is currently outside the safe place. If the player is caught by the predator, it loses all tokens already collected in this epoch, and no more new tokens appear. Magnitude of potential loss therefore corresponds to the number of already collected tokens. Threat level, defined as the wake-up rate, is different for the three predators. This wake-up rate is signalled by different colours, and tailored to result in a wake-up probability of p = 0.1, p = 0.2, or p = 0.3 if the player stays outside the safe place for 100 ms. Participants played 270 epochs (experiment 2: 210 epochs), thus making up to 1620 choices. B: In experiment 3, the task statistics were the same as in experiment 1 but the graphical set up and cover story were entirely different. The player is required to move a virtual “lever”(grey bar at the bottom) to obtain tokens, which can be removed if “static interference” occurred during lever movement.