In related work, researchers such as Antoine Bechara in Iowa and Kevin LaBar at Duke University have shown that the amygdala is also important in acquiring new fear reactions towards previously harmless objects via a procedure know as fear conditioning. This is normally demonstrated by simultaneously presenting an individual with a "neutral" object, such as a cup, together with a mild electronic shock, or startlingly loud noise. As a result, the individual acquires a mild fear towards the previously neutral cup that can be detected as increased galvanic skin response when the cup is presented alone. A similar mechanism is thought to underlie the acquisition of common phobias, such as fear of spiders. Bechara and LaBar showed that individuals with amygdala damage do not show fear conditioning, and concluded that this region plays a central role in this psychological function.

An obvious question was whether emotions other than fear might be associated with relatively specialised brain systems, and there is now good evidence that a brain region known as the insula underlies the recognition of human signals of disgust. Support for this position comes from both brain imaging research and neuropsychological studies of brain-injured patients. A particularly striking example comes from work by my colleagues and I. These researchers studied the performance of a young male with insula damage, known as NK. In a series of experiments they showed that NK demonstrates a highly selective impairment in recognising disgust from facial and vocal signals. In comparison to healthy volunteers with no brain injury, NK also demonstrates a marked reduction in his reactions to disgusting items. For example, in a questionnaire measuring how sensitive an individual is to different disgust-provoking situations, healthy control subjects consistently respond "no" to the question "If you were hungry would you eat a bowl of soup that had been stirred with a washed fly swatter". By contrast, NK was adamant that he would have no difficulty in consuming the soup.