1. A method of processing information, the method comprising: by at least one hardware processor that executes instructions stored in a memory to cause, obtaining stored information indicating correspondences of content time frames indicating time spans for a content viewed by a user and an attention status of the user to the viewed content in a content time frame among the content time frames, the attention status of the user determined from among attention statuses of positive, negative or neutral based on detection results of behavioral states of the user viewing the content in the time spans corresponding to the content time frames; extracting, from among the content time frames in the stored information indicating the correspondences, a plurality of adjacent content time frames corresponding to a plurality of neutral attention states between content time frames corresponding to other than neutral attention states of the user; determining, from among the extracted adjacent content time frames corresponding to the neutral attention states, at least one unordinary attention state transition value indicating at least one unordinary attention state of the user according to a degree of change in an attention state transition value with respect to other attention state transition values of other content time frames in the extracted adjacent content time frames; and in response to the determining of the at least one unordinary attention state of the user, estimating, according to the content time frames in the stored information indicating the correspondences, a content time span of at least one content time frame during the extracted adjacent content time frames which the user has the at least one unordinary attention state, wherein viewed content of the estimated content time frame is used for generation of related content to the viewed content.