Learning device, learning method and program

A learning method performed by a computer, the method comprising:

• a step of extracting a feature quantity from target data;
• a reconstruction step of reconstructing the extracted feature quantity to acquire reconstruction data;
• and
• a step of outputting a reconstruction error, which is a difference between the target data and the reconstruction data, as a degree to which the target data has a feature that a predetermined data group has in common, and
• in the reconstruction step,
• a feature quantity obtained from data belonging to the predetermined data group is separated into a first partial feature quantity and a second partial feature quantity, and
• the second partial feature quantity is exchanged with a second partial feature quantity extracted from another piece of data belonging to the predetermined data group, a post-exchange feature quantity is acquired, and optimization is performed to reduce a difference between data obtained by reconstructing the post-exchange feature quantity and data belonging to the predetermined data group.