PMC

Experimental task. Participants viewed six black and white drawings for 275 ms. A decision screen indicating the amount of money at stake on that trial immediately followed. A coin with “+7kr” indicated that 7 kroner ($1.25) could be won for correct responses and no money would be lost for incorrect responses. On neutral trials the coin was replaced with a white disk and no money could be won or lost. Participants had up to 5 s to make their response. A delay screen was presented for a jittered duration of 3.5 ± 1.5 s immediately following a decision. Upon termination, a feedback screen depicting the money obtained on that trial and the total amount won up to that point was presented (1.75 s). Trials were separated with a jittered ITI of 5 ± 2 s.

: Photo on left: Shell money, E433234, Department of Anthropology, Smithsonian Institution; Photo on right: Metal coin, Opitz, Mogetta, and Terrenato. Sp.Find 956, The Gabii Project: Open Context. ARK: https://n2t.net/ark:/28722/k2697cp2q.

Experimental task. Participants viewed six black and white drawings for 275 msec. A decision screen indicating the amount of money at stake on that trial immediately followed. A gold coin with “+10kr” indicated that 10kr could be won for correct responses and no money would be lost for incorrect responses. On Neg trials the coin was superimposed with “−10kr” and on Neut-P and Neut-N trials the coin was replaced with a white disk. Participants had up to 5 sec to make their response. A delay screen was presented for a jittered duration of 3.5 ± 1.5 sec immediately following a decision. Upon termination a feedback screen depicting the money obtained on that trial and the total amount won up to that point was presented (1750 msec). Trials were separated with a jittered ITI of 5 ± 2 sec.

The incentive force task. Successive screens displayed in one trial are shown from left to right, with durations in ms. Coin images, either one pound (£1) or one penny (1p), indicate the monetary value attributed to the top of the thermometer image. The fluid level in the thermometer represents the online force exerted on the hand grip. The last screen indicates cumulative total of the money won so far.