A study published in October 2025 by the European Broadcasting Union (EBU) in collaboration with the BBC assessed the reliability of the responses provided by the four leading chatbots, ChatGPT, Copilot, Perplexity and Gemini, to news-related queries. In 45 per cent of cases, nearly one in two responses, the study identified shortcomings, some of which were significant. In particular, the chatbots generated information that was wholly or partly fabricated, misinterpreted or distorted the sources cited, drew erroneous links or conclusions, and relied on sources that were out of date, unverifiable or unreliable. The study also highlights errors in the reproduction of quotations, omissions of relevant facts or viewpoints, the inclusion of information unrelated to the query, and a tendency to present opinions or speculation as established facts.
The shortcomings identified affect virtually all the fundamental principles of professional journalism and the obligations of due diligence. They relate in particular to accuracy, timeliness, precision, relevance, completeness, impartiality, and the distinction between facts and opinions. Furthermore, the increasing integration of advertising content into AI models raises new questions regarding the transparency of its identification and the need to put in place effective safeguards to prevent commercial content from being directly incorporated into AI-generated responses.
However, the shortcomings observed cannot be explained solely by the quality of the training data or the sources used by the models. They also stem from certain limitations or characteristics inherent in the way these models operate, which may lead them to produce inaccurate or misleading information, including:
- A tendency towards excessive agreeableness with users, a phenomenon commonly referred to by the English term ‘sycophancy’. Studies show that they are likely to alter initially correct responses when these are challenged, to tailor their responses to users’ presumed opinions or expectations, or even to repeat users’ errors rather than correcting them.
- ‘Hallucinations’, namely responses that appear plausible but are incorrect, fabricated or lacking any factual basis, which they present with great confidence.
- The memory function, available in many chatbots, which enables them to retain certain information across conversations in order to personalize their responses. While this feature can enhance the relevance of interactions, it may also cause the model to incorporate inaccurate information or erroneous assumptions derived from previous conversations. Moreover, taking prior exchanges into account may reinforce the model’s tendency to prioritize the user’s perceived expectations over the factual accuracy of its responses.
The vulnerability of large language models to this type of error can be explained by several factors, notably :
- The quality of the training data, which consists of vast volumes of text sourced from the internet and other sources, and which may contain biases, errors or inaccurate information that the models learn and reproduce.
- The lack of a genuine understanding of the world, which limits the models’ ability to test their responses against verifiable reality, to detect potential logical contradictions in their own responses, and to reliably distinguish between facts, opinions and unfounded claims.
- The difficulty of aligning AI systems with human objectives and values, particularly when concepts such as “truth”, “fairness” or “ethical behaviour” do not lend themselves to an unambiguous definition or to formalisation in the form of rules or learning objectives. This difficulty is particularly significant in areas where there is no objectively correct answer, notably for moral, political or, more broadly, controversial issues.
- The need to reconcile sometimes conflicting objectives, such as the desire to provide a useful response, to ensure its factual accuracy, or to meet users’ expectations. In certain situations, these trade-offs can lead models to prioritise users’ expectations, thereby encouraging sycophantic
- The unintended effects of model alignment through human feedback (‘Reinforcement Learning from Human Feedback’, RLHF). During this training phase, human evaluators assess the model’s responses in order to encourage it to adopt behaviours deemed desirable. However, this process can produce undesirable effects, as human evaluators naturally tend to rate responses more highly if they are sycophantic, validating and confirm their own opinions. The model may thus learn to prioritise responses most likely to be rated positively, rather than the accuracy of its responses, a phenomenon known as ‘reward hacking’. This can result in a tendency to confirm users’ assumptions or opinions, rather than correcting them. An update to GPT-4o rolled out by OpenAI in spring 2025 illustrates this risk. Designed to make the model’s interactions more natural and pleasant, it led to excessively complacent behaviour: the chatbot was too quick to validate users’ statements, agreed with potentially dangerous ideas, encouraged risky behaviour and was at times almost obsequious in its responses. Faced with widespread criticism of this behaviour, OpenAI swiftly withdrew the update.
Given the growing importance of AI-powered chatbots as a source of information, these limitations are no longer merely technical issues. They are likely to influence the formation of individual opinions and, more broadly, the proper functioning of public debate and democratic processes.