Another classic view of attitudes is that attitudes serve particular functions for individuals. That is, researchers have tried to understand why individuals hold particular attitudes or why they hold attitudes in general by considering how attitudes affect the individuals who hold them.[14] Daniel Katz, for example, writes that attitudes can serve "instrumental, adjustive or utilitarian," "ego-defensive," "value-expressive," or "knowledge" functions.[15] The functional view of attitudes suggests that in order for attitudes to change (e.g., via persuasion), appeals must be made to the function(s) that a particular attitude serves for the individual. As an example, the "ego-defensive" function might be used to influence the racially prejudicial attitudes of an individual who sees themselves as open-minded and tolerant. By appealing to that individual's image of themselves as tolerant and open-minded, it may be possible to change their prejudicial attitudes to be more consistent with their self-concept. Similarly, a persuasive message that threatens self-image is much more likely to be rejected.[16]