How is ChatGPT's behavior changing over time?
Authors: name: Lingjiao Chen, name: Matei Zaharia, name: James Zou

GPT-3.5 and GPT-4 are the two most widely used large language model (LLM)
services. However, when and how these models are updated over time is opaque.
Here, we evaluate the March 2023 and June 2023 versions of GPT-3.5 and GPT-4 on
four diverse tasks: 1) solving math problems, 2) answering sensitive/dangerous
questions, 3) generating code and 4) visual reasoning. We find that the
performance and behavior of both GPT-3.5 and GPT-4 can vary greatly over time.
For example, GPT-4 (March 2023) was very good at identifying prime numbers
(accuracy 97.6%) but GPT-4 (June 2023) was very poor on these same questions
(accuracy 2.4%). Interestingly GPT-3.5 (June 2023) was much better than GPT-3.5
(March 2023) in this task. GPT-4 was less willing to answer sensitive questions
in June than in March, and both GPT-4 and GPT-3.5 had more formatting mistakes
in code generation in June than in March. Overall, our findings shows that the
behavior of the same LLM service can change substantially in a relatively short
amount of time, highlighting the need for continuous monitoring of LLM quality.