Figure 3.

Pharmacological manipulation of cognitive effort is dissociated from visuospatial attention and motor impulsivity. (a) d-amphetamine significantly attenuated the heterogeneity of choice behavior, making workers ‘slack off' and slackers ‘work harder' (dose × group: p=0.016). Choice behavior for workers and slackers was significantly different at saline and 0.3 mg/kg (group: all p<0.002) but indistinguishable after 0.6 and 1.0 mg/kg. (b) Although mild impairments of accuracy were observed for workers' high-effort/HR trials at 0.6 mg/kg (p=0.032), amphetamine had no main effect on accuracy for all animals. (c) Despite amphetamine's opposing effects on the choice behavior of workers and slackers, the psychostimulant significantly increased motor impulsivity for all animals in both trial types (dose: p=0.008). (d–f) Ethanol had no effects on choice, accuracy, or premature responding for all animals. (g) Caffeine reduced workers' choice of HR trials (dose: p=0.008) but had no effect on slackers' choice behavior. (h) Caffeine had no effects on accuracy for all animals. (i) Caffeine modestly increased premature responding for all animals when both trial types were considered together (dose: p=0.029). Data are shown as the mean percent choice for each option (±SEM).