BIS/BAS Scales
The Behavioral Inhibition System (BIS) responds to cues of punishment, non-reward, and novelty. It's the "stop and check" system.
The Behavioral Activation System (BAS) responds to cues of reward and non-punishment. It's the "go for it" system.
Developed by Carver & White (1994), the BIS/BAS Scales measure individual differences in these two fundamental motivational systems.