p018fig01.12 Peak shift and behavioural contrast.  When a negative generalization gradient (in red) is subtracted from a positive generalization gradient (in green), the net gradient (in purple) is shifted way from the negative gradient and has a width that is narrower than any of its triggering gradients.  Because the total activity of the network tends to be normalized, the renormalized peak of the net gradient is higher than that of the rewarded gradient, thereby illustrating that we can prefer experiences that we have never previously experienced over those for which we have previously been rewarded.<BR>||