It is not well known how these are developed many believe that they come from past experiences, pleasant experiences or unpleasant ones can influence how a person's attitudes are formed towards a specific thing. This explanation implies that attitudes could be unpleasant if the previous experience was also an unpleasant one, they can also be formed because of early experiences in the early stages of life. Another possible explanation is the fact that implicit attitudes can also stem from affective experiences, there is evidence that the amygdala is involved in affective or emotional reactions to stimuli. A third explanations involves cultural biases, this was shown in a study done by Greenwald, McGhee, and Schwartz (1998) that in-group bias was more prevalent when the in-group was more in tune with their ancestral culture (for example knowing the language).