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Task Competence Is Not Instruction Following: Evaluating Instruction-Conflicting Behavior in Small Language Models

Summary

Small language models are often competent at tasks but fail to follow instructions when they conflict with standard behavior. Larger models show a clearer gap between standard and non-standard instruction accuracy. The study demonstrates that task ability and instruction following are distinct capabilities.

SourcearXiv Computational LinguisticsAuthor: Mahdiyeh Farajidizaji, Vatsal Raina
Task Competence Is Not Instruction Following: Evaluating Instruction-Conflicting Behavior in Small Language Models
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[Submitted on 21 Jul 2026]

Title:Task Competence Is Not Instruction Following: Evaluating Instruction-Conflicting Behavior in Small Language Models

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Abstract:Instruction tuning is meant to make language models follow user requests, yet it is unclear whether small models comply when an instruction conflicts with their usual task behavior. We study this across three tasks - multiple-choice question answering (MCQA), sentiment classification, and mathematical question answering - by pairing a standard instruction with a conflicting non-standard one (select an incorrect option, output the opposite sentiment, or return twice the answer). This cross-task design allows us to test whether resistance to conflicting instructions is tied to specific task characteristics or reflects a broader behavioral tendency. As all predictions are scored against the original ground truth, a model that ignores the non-standard instruction still appears accurate. Using standard accuracy, non-standard accuracy, and an Instruction-Following Failure Rate (IFFR), we evaluate instruction-tuned Qwen models across sizes. Both standard accuracy and instruction following generally improve with scale, although the pattern is not consistent across all tasks and datasets. Small models stay competent yet routinely ignore the non-standard instruction, while larger models show a clear gap between the two settings. These findings suggest that gains in task capability do not automatically provide reliable control over model behavior. Task competence and instruction following are therefore distinct abilities, and reporting only standard accuracy hides instruction-following failures.

Comments: 12 pages, 4 figures, 8 tables

Subjects:

Computation and Language (cs.CL)

Cite as: arXiv:2607.19608 [cs.CL]

(or arXiv:2607.19608v1 [cs.CL] for this version)

https://doi.org/10.48550/arXiv.2607.19608

arXiv-issued DOI via DataCite (pending registration)

Submission history

From: Vatsal Raina [view email] [v1] Tue, 21 Jul 2026 22:24:18 UTC (81 KB)

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Key points

  • Small models maintain task accuracy but routinely ignore conflicting instructions.
  • Larger models show a clearer gap between standard and non-standard instruction performance.
  • Task competence and instruction following are separate abilities; reporting only standard accuracy hides instruction-following failures.

Highlights and analysis are generated automatically and may contain errors. Check the original source.