Skip to content
Submit incident
AII-1001-50951
ConfirmedA court, a regulator or the organization itself has stated the core facts, or the record cites a court or regulator source.

MIT researchers reveal LLMs learn incorrect syntactic patterns during training

MIT researchers found that large language models can learn incorrect grammatical patterns during training and rely on these patterns instead of reasoning, potentially producing unreliable answers in customer service, clinical documentation, and financial reporting tasks. The vulnerability could also be exploited by malicious actors to bypass model safeguards.

25 November 2025 Β· Reliability and hallucination
25 November 2025
AII-1001-50951View source β†—
Quick facts
Category
Reliability and hallucination
Country
United States
Source
EurekAlert!
Date
25 November 2025
Drafted by
Raidu Incident Detection

What happened

MIT researchers discovered that large language models can learn to mistakenly link certain sentence patterns with specific topics during training, then repeat these patterns instead of reasoning through problems.

An LLM given a question with the same grammatical structure as training examples but with nonsense words might provide a convincing answer by recognizing familiar sentence patterns instead of understanding the actual question.

The researchers found that even the most powerful LLMs can make this mistake, which they call reliance on incorrect 'syntactic templates' learned from parts-of-speech patterns in training data.

Reported impact

This shortcoming could reduce the reliability of LLMs performing tasks like handling customer inquiries, summarizing clinical notes, and generating financial reports.

A nefarious actor could exploit this vulnerability to trick LLMs into producing harmful content, even when the models have safeguards to prevent such responses.

Index analysis

The researchers developed a benchmarking procedure to evaluate a model's reliance on these incorrect correlations to help developers mitigate the problem before deploying LLMs.

Governance controls

The shortcoming is a byproduct of how models are currently trained, but the researchers note that models are now deployed in safety-critical domains far beyond the tasks that created these syntactic failure modes.

Classification

Category
Reliability and hallucination
Industry
Media, social platforms and marketing
Country
United States
Harm status
Potential harm
Intent
Unintentional
Timing
Post-deployment
Harm types
Public interest
Harmed
Consumers, Business
Failure modes
Hallucination, Overreliance
AI systems
Large Language Models

Sources and evidence

This record was researched and written by the Index, based on the following original reporting.

EurekAlert!
Researchers discover a shortcoming that makes LLMs less reliable
25 November 2025
Jul 2026Instagram AI System Deletes Dozens of Iraqi User AccountsWell documentedReliability and hallucinationΩ…ΩˆΨ³ΩˆΨΉΩ‡ Ψ§Ω„ΨΉΨ±Ψ§Ω‚ΩƒΨͺΨ§Ψ¨Ψ§Ψͺشفق Ω†ΩŠΩˆΨ²+1Jul 2026Meta's AI Missubtitles Melissa Naschenweng Concert VideoWell documentedReliability and hallucinationHeute.atT-online.deBunte+5Jun 2026Meta AI Auto-Alter Creates Defective Bike in REI Instagram AdWell documentedReliability and hallucinationCarscoopsInc.The Seattle Times+1Apr 2026AI Chatbots Found to Dispense Inaccurate and Potentially Harmful Medical AdviceConfirmedReliability and hallucinationBloomberg BusinessThe IndependentDaily Mail Online+4Feb 2026AI chatbots give inaccurate health advice, Oxford study findsConfirmedReliability and hallucinationToronto SunDaily Mail OnlineDaily Sabah+2