Table 2.

Top 20 parts-of-speech comparison between human-written and ChatGPT-generated text in the medical abstract and radiology report data sets.

Category	Medical abstract data set			Radiology report data set
	Human (n=294,700), n (%)	ChatGPT (n=1,358,297), n (%)	Human (n=263,097), n (%)		ChatGPT (n=1,047,319), n (%)
Noun, singular or mass	66,052 (22.4)	315,326 (23.2)	65,678 (25)		265,415 (25.3)
Adjective	45,157 (15.3)	209,179 (15.4)	48,690 (18.5)		196,195 (18.7)
Preposition or subordinating conjunction	42,496 (14.4)	182,029 (13.4)	25,070 (9.5)		96,548 (9.2)
Determiner	25,947 (8.8)	127,371 (9.4)	22,720 (8.6)		106,668 (10.2)
Noun, plural	23,918 (8.1)	122,615 (9)	9511 (3.6)		57,902 (5.5)
Coordinating conjunction	11,292 (3.8)	56,301 (4.1)	7305 (2.8)		41,160 (3.9)
Cardinal digit	10,718 (3.6)	25,053 (1.8)	4132 (1.6)		8881 (0.8)
Verb, past tense	10,613 (3.6)	47,084 (3.5)	3000 (1.1)		8839 (0.8)
Verb, past participle	10,517 (3.6)	44,381 (3.3)	8935 (3.4)		40,067 (3.8)
Proper noun, singular	10,075 (3.4)	51,644 (3.8)	30,463 (11.6)		90,531 (8.6)
Adverb	7311 (2.5)	22,606 (1.7)	6142 (2.3)		14,082 (1.3)
To	4646 (1.6)	26,474 (1.9)	2424 (0.9)		10,533 (1)
Verb, base form	4569 (1.6)	27,916 (2.1)	2527 (1)		8501 (0.8)
Verb, third person singular present	3928 (1.3)	20,371 (1.5)	10,877 (4.1)		40,737 (3.9)
Verb, gerund or present participle	3760 (1.3)	30,265 (2.2)	2492 (0.9)		9304 (0.9)
Verb, nonthird person singular present	3237 (1.1)	13,166 (1)	3950 (1.5)		25,160 (2.4)
Personal pronoun; possessive pronoun	1681 (0.6)	5775 (0.4)	—a		—
Modal	1663 (0.6)	6717 (0.5)	970 (0.4)		2023 (0.2)
Adjective, comparative	1311 (0.4)	4724 (0.3)	1401 (0.5)		3114 (0.3)
Wh-determiner	937 (0.3)	2793 (0.2)	655 (0.2)		1257 (0.1)
Existential there	—	—	3925 (1.5)		11075 (1.1)

^aNot in the top 20 parts-of-speech.