Research over the past several decades has shown that intergroup contact can be an effective strategy for reducing discrimination. In 1954, Allport defined 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 by Sherif. Although these four factors can lead to optimal results, depending on the situation, positive results can be achieved even if all four factors are not satisfied. Furthermore, the historical nature of the relations between the target groups defines which of the conditions will be most important. If the historical nature of the relationship has been quite strained (for example in the case of groups with a clear history 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 to achieve the best intergroup outcomes. If groups have had strained relationships, institutional support is a necessary condition for advantageous intergroup contact. Since beneficial outcomes between groups can only be achieved through positive interactions, contacts that cause anxiety or lead to physical and emotional violence should be avoided. Since 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.) that are recognized by both groups can change social norms so that contact between the groups appears accepted...... middle of paper ...... which may deviate from social norms, this can lead to anxiety. Due to anxiety, initial interactions between members of different groups may not result in a positive outcome. However, if contact is repeated several times, it will allow individuals to establish a relationship (and potentially a friendship). As this occurs, individuals become more accepting of the interaction and experience a decrease in anxiety over time. Therefore, if the contact lasts longer, the probability of a positive result increases. Depending on the situation, not all of Allport's four conditions for optimal contact may be necessary; for groups with a history of strained relationships, institutional support is necessary, for groups with less strained relationships, interdependence is necessary. Additionally, in order to achieve the best result, positive contact must be established over a long period of time..