See the methods: as usual for visual fixattion experiments with monkeys, the subjects were trained to maintain fixation, fixation window being only a part of th

See the methods: as usual for visual fixattion experiments with monkeys, the subjects were trained to maintain fixation, fixation window being only a part of the image size: stimulus size spanned 5.7 degrees. The fixation spot size was 0.2 degrees in diameter and the fixation window was a square with the diameter of 2.5 degrees. 2.5 is relatively large in my experience, might be due to lots of noise on the signal, but anyway there won't be true saccades (well, there shouldn't be, parts of recorded data wehere with saccades outside of that fixation window should get rejected). Probably microsaccades were present, but those aren't mentioned.