Research over the past few decades has shown that intergroup contact can be an effective strategy for reducing discrimination. In 1954 Allport outlined four conditions for optimal contact; equal status in the situation, common goals, cooperation and institutional support. Common goals and cooperation were later combined as interdependence on the sheriff. Although these four factors can lead to optimal results, depending on the situation, it is possible to achieve positive results even if all four factors are not met. Furthermore, the historical nature of the relationship between the target groups defines which of the conditions will be the most important. If the historical nature of the relationship has been somewhat strained (as in the case of groups that have overt histories of intergroup violence), then institutional support is the most important factor. However, for groups that have had less strained relationships, interdependence is the most important factor in achieving a positive outcome. In addition to Allport's four conditions, long-term contact is also necessary for best intergroup results. If groups have had strained relationships, institutional support is a necessary condition for beneficial intergroup contact. Because beneficial intergroup outcomes are only achieved through positive interactions, contact that causes anxiety or leads to physical and emotional violence should be avoided. Because anxiety or violence is likely to arise in situations of natural contact between two groups that have had strained relationships, institutional support can help restructure the interaction in a positive way. Institutions (laws, culture, officials, etc.) recognized by both groups can modify social norms to make contact between the groups seem accepted...... middle of paper ......nce which can deviate from social norms, can lead to anxiety. Due to anxiety, early interactions between members of different groups may not be able to lead to a positive outcome. However, if contact is repeated multiple times, it will allow individuals to establish a relationship (and potentially a friendship). When this happens, individuals become more accepting of the interaction and see a decrease in their anxiety over time. Therefore, if the contact lasts longer, the probability of a positive outcome increases. Depending on the situation, Allport's four conditions for optimal contact may not all be necessary; for groups with a history of strained relationships institutional support is needed, for groups with less strained relationships interdependence is needed. Furthermore, to achieve the best result, positive contact must occur over a long period of time.