Are positive and negative feedback weighed in a common balance in the brain, or do they influence behaviour through distinct neural mechanisms? Recent neuroeconomic studies in both human and non-human primates indicate that the ventromedial frontal lobe carries information about both losses and gains, suggesting that this region may encode value across the continuum from absolute negative to absolute positive outcomes. However, such work does not specify whether or how this value information is applied during behaviour. Observations of patients with ventromedial frontal damage indicate that this region is critical for certain forms of reinforcement learning and value-based decision-making, but the underlying processes remain unclear. We disentangled the influence of cumulative positive and negative feedback on subsequent behaviour with a probabilistic reinforcement learning task in 11 patients with ventromedial frontal damage, 9 lesioned controls and 24 healthy controls, and found that ventromedial frontal damage selectively disrupted the ability to learn from negative feedback.