In treating patients with phobias, therapists address the emotion of fear and try to alter that emotion so the patient is no longer afraid. However, patients with what doctors call blood-injection-injury phobia experience more difficulty with treatment. It includes people who fear needles, blood, and surgery.

Scientists have determined that this phobia has been tough to treat because it doesn't just involve fear, but involves disgust too. Thus, to better treat these patients therapists need to distinguish between these emotions and treat each one separately. To determine how people with and without this blood-injection- phobia distinguish between fear and disgust, the researchers subjected them to a visual test.

Subjects were shown various images of surgeries, needle sticks, rotting food, feces, and more neutral images such as tools. After each image they were shown facial expressions depicting fear, disgust, and neutrality. Each image was shown with each facial expression the same number of times; but when asked to report the percentage of times particular facial expressions were paired with particular images, the subjects' perceptions were inaccurate.

They estimated that the surgery and injection images were paired equally with expressions of fear and disgust. But they estimated that the rotting food and feces images were paired primarily with expressions of disgust and that the images of tools were paired primarily with expressions of neutrality. The experiment shows the subjects' own biases as to what they find disgusting or fearful, information that may prove useful in helping doctors separate the two emotions in treating patients with this phobia.