3. The apparatus of claim 1 , wherein the computing unit computes a first vector and a plurality of second vectors, the first vector having the emotion correlation between the word and the one or more comparison words as an element, the second vectors having the emotion correlations between the plurality of reference words and the one or more comparison words as elements, and the computing unit computes the plurality of first absolute emotion similarity values by using angles between the first vector and the plurality of second vectors, and computes the at least one second absolute emotion similarity value by using angles between the plurality of second vectors.
3. The apparatus of claim 1 , wherein the computing unit computes a first vector and a plurality of second vectors, the first vector having the emotion correlation between the word and the one or more comparison words as an element, the second vectors having the emotion correlations between the plurality of reference words and the one or more comparison words as elements, and the computing unit computes the plurality of first absolute emotion similarity values by using angles between the first vector and the plurality of second vectors, and computes the at least one second absolute emotion similarity value by using angles between the plurality of second vectors. 4. The apparatus of claim 3 , wherein the computing unit computes a relative emotion similarity value between the word and each the plurality of reference words (a plurality of relative emotion similarity values) by using the plurality of first absolute emotion similarity values and the at least one second absolute emotion similarity value, and the prediction unit predicts the pleasantness-unpleasantness index of the word by using the plurality of relative emotion similarity values and the pleasantness-unpleasantness index of the plurality of reference words, and an i-th relative emotion similarity value from among the plurality of relative emotion similarity values is computed using an i-th first absolute emotion similarity value between the word and an i-th reference word from among the plurality of reference words and second absolute emotion similarity values between the i-th reference word and the reference words of the reference word set other than the i-th reference word.