This element refers to actual cause and proximate cause. The most common test of proximate cause under the American legal system is foreseeability. All forms are either specifically proximate, or can be either proximate or obviate. Demonstrative pronouns distinguish between proximate and remote. Some jurisdictions recognize five elements, duty, breach, actual cause, proximate cause, and damages. As colleges acquired physical facilities, visible campuses formed with a proximate student population. An increase in interference already occurred with some other prior proximate band usages. Zero-sum thinking is the result of both proximate and ultimate causes. A related doctrine is the insurance law doctrine of efficient proximate cause. This view also circumvents the problem of infinite regression of 'why's that proximate causes create. These have helped in finding the proximate causes of circadian and seasonal cycles. The doctrine of proximate cause is notoriously confusing. There are several competing theories of proximate cause (see Other factors). This is known as the principle of proximate cause.