cs.HCAug 31, 2026

Frontier vision-language models have overtaken young adults at detecting AI-generated portraits -- but not their calibration

Authors: Sunwhi Kim, Sunyul Kim, Meounggun Jo, Jini Tae

Organizations: Hwasung Medi-Science University, Dept. of Bio-Healthcare · Hwasung Medi-Science University, Dept. of Bio-Healthcare, Republic of Korea · Yonsei University, Graduate School of Engineering, Dept. of Artificial Intelligence · Yonsei University, Graduate School of Engineering, Dept. of Artificial Intelligence, Republic of Korea · Hoseo University · Hoseo University, Republic of Korea · Gwangju Institute of Science and Technology, School of Humanities and Social Sciences · Gwangju Institute of Science and Technology (GIST), School of Humanities and Social Sciences, Republic of Korea

Abstract

AI image generators now create face portraits that are hard to tell from real photographs. Vision-language models (VLMs) are increasingly proposed to flag such images. We benchmarked 19 VLMs on the same 198 face portraits -- real photographs and identity-matched ChatGPT-4o and Imagen 3 versions -- under the same task as our earlier study of 1,667 adults (85% correct overall; accuracy fell steeply with age). The June-2026 cohort of 14 models only matched adults in their 20s-30s. Four weeks later the ceiling broke. Among five July-2026 releases under the identical protocol, gpt-5.6-sol reached 92.8% balanced accuracy (five-draw mean 92.1%), clearly above adults in their 20s (88.5%), and claude-fable-5 detected every AI image while averaging 91.9%. Model sensitivity now exceeds young adults decisively (d' up to 3.4 versus ~ 2.4). What has not been overtaken is human calibration. Model criteria spread from c = -1.10 to +1.45 while humans sit near zero at every age; both new leaders are biased (+0.44, -0.97), and only a few mid-ranked models approach the human balance. Changing the labelled examples still flipped about one answer in four. The best machines now out-see young adults here, without matching the human balance between suspicion and trust.

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