The positive patterning procedure involves presenting simultaneous compound stimuli that are paired with reinforcement (AB+) while withholding reinforcement when a single stimulus is presented (A-, B-). Positive patterning produces an increase in responding to the compound stimuli and a decrease in responding to a single stimulus.
An example of positive patterning is present in the daily medicinal routine of an asthmatic. To prevent an asthma attack, the person has to take two medicines: one that opens the patient's lungs and another to enhance breathing capabilities. When the medicines are taken simultaneously, the asthmatic's lungs are opened, breathing is improved, and therefore an asthma attack is prevented. However, if each medicine is taken alone an asthma attack may still occur. As a result of the medicines preventing an attack when taken simultaneously, the patient is more likely to take the drugs together than separately.
The negative patterning procedure also involves presenting simultaneous compound stimuli. However, the simultaneous compound stimuli are not paired with reinforcement (AB-) while the stimuli presented individually are paired with reinforcement (A+, B+). Negative patterning decreases responding to the compound stimuli and increases responding to the stimuli presented individually.
Students frequently encounter examples of negative patterning. As a result of poor performance on a midterm you are prompted to study intensely for the final to raise your class grade. As a result of poor performance on quizzes in another class, you are again prompted to study intensely for the final to raise your grade. However, if you perform poorly on the midterm and on quizzes in the same class, you will not be prompted to study at all for the final because a high grade on the final can't raise your overall grade in the class. Therefore, you will be more likely to study for final exams when you have performed poorly on a midterm in one class and quizzes in another.