1. A perceptual reaction analyzer that transmits content to a plurality of terminals connected via a network and estimates presence/absence of interest of users of the plurality of terminals, based on perceptual reaction information generated by each of the terminals detecting perceptual reaction of the user of the terminal on the content for a predetermined period, the perceptual reaction analyzer comprising: a content transmitting unit configured to perform a content transmitting processing to transmit content to the terminals; a perceptual reaction information receiving unit configured to perform a perceptual reaction information receiving processing to receive the perceptual reaction information detected by each of the plurality of terminals; a perceptual reaction change generating unit configured to perform a perceptual reaction change information generating processing to generate perceptual reaction change information which indicates a change of perceptual reaction of the users of the plurality of terminals based on the received perceptual reaction information; a user grouping unit configured to perform a user grouping processing to estimate the presence/absence of interest of the users of the plurality of terminals based on the perceptual reaction change information, and classify the users into groups corresponding to the presence/absence of the interest; a certainty level generating unit configured to perform a certainty level generating processing to generate a certainty level which indicates a degree of certainty of the presence/absence of interest estimated for each user based on the perceptual reaction change information; and a perceptual reaction trial unit configured to perform a perceptual reaction trial processing to try, for a low certainty user of which certainty level is lower than a threshold, an operation on the content corresponding to the perceptual reaction by which the same presence/absence of interest of the low certainty user is estimated again, based on the perceptual reaction information of a user of which presence/absence of interest is the same as the low certainty user, wherein the perceptual reaction information receiving processing, the perceptual reaction change information generating processing and the user grouping processing are performed after the perceptual reaction trial processing, such that interest re-estimating processing to estimate the presence/absence of interest of the low certainty user with respect to the tried operation is performed.