A method of outputting content by a device includes obtaining attribute information about review content that is retrieved by the device; estimating an amount of user's memory about the review content at a preset time based on the obtained attribute information and reference information obtained after the review content is selected; comparing the estimated amount of the user's memory and a threshold value; and changing appearance of the review content in response to the amount of the user's memory being determined as equal to or less than the threshold value.