Article Figures & Data
Figures
- Figure 1.
The options for each choice—Play or Quit—appeared randomly on the left and right side of the computer display during the decision phase. Each round began with a loss (also the stake) displayed for 3 s. This was followed by a choice to accept that loss (Quit) and end the round or to risk the value of the loss (Play) to try and recover it. Subjects responded by pressing keys on a mouse corresponding to the side of their desired choice. Choices were randomly assigned to sides of the display from round to round. Outcome displays (2 s) indicated whether subjects had won a gamble and that no money was lost (Play & Win); whether they had lost a gamble and the amount lost (Play & Lose); or the amount lost from assets if subjects chose to give up (Quit). If the loss reached 6400 kr, the round automatically ended with no chance of recovery (Play & Lose Max). At the end of each round, subjects were informed of the amount that would be taken off their final total as a result of that round. There was no time limit for making a decision. The dotted line indicates the subject's choice but was not displayed to subjects. Words were translated to Danish. Displays were presented to subjects in color with losses, negative outcomes, and Quit displays indicated in red font. Positive outcomes were indicated in green.
- Figure 2.
Interaction of drug and stake on risky persistence. Probability of decision to accept a double-or-nothing gamble across various magnitudes of stake. Gambling probability was reduced with increasing stakes in the placebo group but not the MPH group (see Table 2). This led to a significant difference of gambling probability at high stakes (1600 kr). Error bars are ±1 SE (between subjects). *p < 0.05.
Tables
Measure Drug group Placebo MPH Mean SD Mean SD Plays: all choices 0.69 0.14 0.73 0.12 Switches from previous: all choices 0.44 0.16 0.40 0.14 Mean stake Play: mean overall stake 0.87 0.22 1.03 0.15 Mean stake Quit: mean overall stake 1.12 0.41 0.93 0.41 Deliberation time, Play (ms) 1045 296 1329 549 Deliberation time, Quit (ms) 1196 414 1434 500 Money lost (kr) 47,031 16,988 58,843 17,239 β SE Z p > z SDRE Stake × drug Intercept 1.1315 0.1658 6.826 0.00 0.92 Stake (100 kr units) −0.4595 0.2609 −1.761 0.08 1.41 Drug: MPH (1) /placebo (−1) 0.1387 0.1658 0.837 0.40 Drug × stake 0.633 0.2609 2.426 0.015* MPH Intercept) 1.24 0.17 7.29 0.00* 0.59 Stake 0.16 0.38 0.43 0.66 1.40 Placebo Intercept 0.96 0.31 3.04 0.002* 1.34 Stake −1.14 0.44 −2.59 0.009* 1.78 ↵*p < 0.05.
β SE Z p > z SDRE Game losses × drug group Intercept 0.96 0.12 7.8 0.00 0.75 Game losses (1000 kr units) −0.01 0.00 −2.4 0.02* 0.00 Drug: MPH (1)/placebo (−1) 0.11 0.12 0.86 0.39 Game losses × drug 0.01 0.00 2.18 0.03* MPH Intercept 1.08 0.15 7.01 0.00 0.55 Game losses 0.00 0.00 0.01 1.00 0.00 Placebo Intercept 0.84 0.20 4.24 5.06 0.81 Game losses −0.014 0.004 −3.38 0.00* 0.00 ↵*p < 0.05.
