Provided is an estimation method for measuring and analyzing brain activity to estimate a perceptual semantic content thereof. This method comprises: (A) inputting, to a data processing means, brain activity induced in a subject by a training stimulation and detected as an output of a brain activity detection means and an annotation of a perceptual content； (B) associating a sematic space representation of the training stimulation and the output of the brain activity detection means in a stored semantic space and storing the association in a training result information storage means； (C) inputting, to the data processing means, an output when the brain activity detection means detects brain activity induced by a novel stimulation, and obtaining a probability distribution in the semantic space which represents perceptual semantic contents for the output of the novel stimulation-induced brain activity by the brain activity detection means on the basis of the association； and (D) estimating a highly probable perceptual semantic content on the basis of the probability distribution. The association process may be performed for each subject in the probability estimation process, the likelihood calculated on the basis of the coordinate of a given word in the semantic space and the probability distribution is used as an indicator.
