Physiologist Ivan Pavlov conditioned dogs to associate food with the sound of a buzzer, which left them salivating. Decades later, researchers discovered such training appears to block efforts to teach the animals to link other stimuli to the same reward. Dogs trained to expect food when a buzzer sounds can then be conditioned to salivate when they are exposed to the noise and a flash of light simultaneously. But light alone will not cue them to drool. This ‘blocking effect’ -- a well-known behavior in psychology, linked to learning -- underpins the idea that surprising or unexpected experiences drive learning. A dog being trained to associate a sound with the arrival of food will at first find that noise novel — reinforcing the notion that sound equals kibble. Once that link is made, any attempt to link another stimulus to the delivery of food will seem redundant, and fail. Studies of the brain’s dopamine system seem to confirm this idea: the levels of dopamine — a chemical that signals pleasure — surge higher after an unexpected reward than an expected one. But the latest study by psychologists in Belgium suggests that the process of learning might be more complicated than scientists had realized. They failed to replicate the effect in 15 independent experiments. Their research is part of a broader push in the social sciences to test the reliability of published results — an effort that has led some researchers to suggest there is a ‘replication crisis’ afoot, because many results that seem solid cannot be reproduced. http://www.nature.com/news/psycholo...ll-known-behaviour-linked-to-learning-1.20659
