Confirmation bias
Confirmation bias is a form of statistical bias, describing the tendency to seek for or interpret evidence in ways that support one's existing beliefs. After a consumer creates a preference of one brand over others, any additional feature that may be common between various brands will most likely only strengthen the consumer's pre-existing preference, causing them to disregard other brands. Hence, a positive brand equity may not be as influential if a consumer already has a pre-existing brand preference.