Distinguishing ChatGPT(-3.5, -4)-generated and human-written papers through Japanese stylometric analysis

Text-generative artificial intelligence (AI), including ChatGPT, equipped with GPT-3.5 and GPT-4, from OpenAI, has attracted considerable attention worldwide. In this study, first, we compared Japanese stylometric features generated by GPT (-3.5 and -4) and those written by humans. In this work, we performed multi-dimensional scaling (MDS) to confirm the distributions of 216 texts of three classes (72 academic papers written by 36 single authors, 72 texts generated by GPT-3.5, and 72 texts generated by GPT-4 on the basis of the titles of the aforementioned papers) focusing on the following stylometric features: (1) bigrams of parts-of-speech, (2) bigram of postpositional particle words, (3) positioning of commas, and (4) rate of function words. MDS revealed distinct distributions at each stylometric feature of GPT (-3.5 and -4) and human. Although GPT-4 is more powerful than GPT-3.5 because it has more parameters, both GPT (-3.5 and -4) distributions are likely to overlap. These results indicate that although the number of parameters may increase in the future, AI-generated texts may not be close to that written by humans in terms of stylometric features. Second, we verified the classification performance of random forest (RF) for two classes (GPT and human) focusing on Japanese stylometric features. This study revealed the high performance of RF in each stylometric feature. Furthermore, the RF classifier focusing on the rate of function words achieved 98.1% accuracy. The RF classifier focusing on all stylometric features reached 100% in terms of all performance indexes (accuracy, recall, precision, and F1 score). This study concluded that at this stage we human discriminate ChatGPT from human limited to Japanese language.Comment: 15 pages, 5 figures, 5 table

Contraction of perceived size and perceived depth in mirrors

We investigated how size and depth are perceived in a plane or convex
 mirror. In Experiment 1, using a plane or convex mirror, 20 observers
 viewed a separation between two objects that were presented at a constant
 distance and reproduced it by a separation between other two objects in a
 natural viewing situation. The mean matches generally approximated the
 real size of the standard and did not equal either virtual size or visual angle of
 the standard. In addition, the mean matches obtained with convex mirrors
 were reduced by about 7% in comparison with those obtained with the plane
 mirror. In Experiment 2, we examined whether the perceived depth in a
 convex mirror is comparable to that in a plane mirror. We presented
 isosceles triangles on a table and required 12 observers to observe them with
 a plane or convex mirror. With the method of limits, we determined the
 triangle that was perceived as an equilateral triangle. When the apexes of
 isosceles triangles were directed to the observer or to depth, the ratio of
 height to base was larger in convex mirrors than in the plane mirror,
 whereas when the apexes were directed to left or to right, the ratio of height
 to base was smaller in the convex mirrors than in the plane mirror. The
 contraction of perceived depth amounted to about 6% in convex mirrors.
 The results of both experiments suggest that although separation and depth
 in convex mirrors appear to reduce, there is a strong tendency that visual
 system recovers the optical distortions by convex mirrors