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SETLEXSEM CHALLENGE: Using Set Operations to Evaluate the Lexical and Semantic Robustness of Language Models
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Introduces SetLexSem, a synthetic benchmark of set operations (union, intersection, difference, symmetric difference) that systematically varies lexical and semantic properties of set members to test LLM robustness, finding poor robustness especially on semantically "deceptive" sets.
Problem
LLMs are evaluated on algorithmic tasks with limited, possibly leaked datasets, and their accuracy may vary with incidental features such as operation type, operand size, token type, length, frequency, and semantic relatedness of set members. The paper asks whether LLMs perform set operations robust
Approach
Uses finite set operations as a controllable synthetic probe: operands can be any nameable symbols, so lexical form, corpus frequency, token length, and WordNet hypernym-based semantic groupings ("deceptive" sets) can be varied systematically while the algorithm stays fixed. The figure of merit is variance of accuracy rather than mean accuracy, interpreted as System 2 robustness.
Key results
- Across seven LLMs' prompts, mean accuracy ranged from 69.37 (Claude Instant) to 85.09 (GPT-3.5), with high standard deviations (16 to 36).
- Accuracy falls with operand size (90.38 at size 2 to 54.4 at size 16) and is lowest for symmetric difference (65.25) versus union (88.88).
- On deceptive sets (Claude Haiku), swapped sets reached 71.88 mean accuracy with SD 26.41, versus 91.84 for not-swapped and 81.06 for random baseline.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Swap half of the semantically grouped words between sets | Claude Haiku on SetLexSem deceptive words · SetLexSem deceptive words | accuracy: 91.84 -> 71.88 | Hurt |
| Use semantically uniform sets instead of randomly sampled words | Claude Haiku on SetLexSem · SetLexSem deceptive words vs random baseline | accuracy: 81.06 -> 91.84 | Helped |
| Increase operand size from 2 to 16 | All evaluated LLMs on SetLexSem · SetLexSem | accuracy: 90.38 -> 54.4 | Hurt |
| Use symmetric difference instead of union | All evaluated LLMs on SetLexSem · SetLexSem | accuracy: 88.88 -> 65.25 | Hurt |
| Use formal rather than plain-language prompting | Evaluated LLMs on SetLexSem · SetLexSem | accuracy: 72.2 -> 76.8 | Helped |
| Use tokens of length 5 rather than length 3 | Claude Haiku on SetLexSem · SetLexSem, frequency deciles 2nd–9th | accuracy: 16.6; 11.2; 6.4; 1.7; 4.9; 4.2; 2.5; 3.8 | Helped |
| Increase number token length from 1 to 4 | Claude Haiku on SetLexSem · SetLexSem numbers | accuracy: 93.5 -> 73.2 | Hurt |
| Increase word token length from 1 to 4 | Claude Haiku on SetLexSem · SetLexSem words | accuracy: 86.0 -> 95.3 | Helped |
| Increase operand size from 2 to 4 | Claude Haiku on SetLexSem · SetLexSem numbers | accuracy: 90.5 -> 77.6 | Hurt |
| Increase operand size from 2 to 4 | Claude Haiku on SetLexSem · SetLexSem words | accuracy: 94.7 -> 88.5 | Hurt |
| Use words rather than numbers | Claude Haiku on SetLexSem · SetLexSem | accuracy: Numbers: 93.5, 85.0, 84.5, 73.2; Words: 86.0, 91.6, 93.5, 95.3 | Mixed |
| Increase demonstrations from 0 to 5 with CoT and self-reflection, allowing empty sets (ablation) | Claude Haiku on SetLexSem · SetLexSem numbers | accuracy: 83.6 -> 88.0 | Helped |
Surprising findings
- Semantically uniform deceptive sets were easier than random words, but swapping half the members within sets produced a sharp failure mode with intersection accuracy of 50.12%.
- Accuracy was higher for words than numbers in most conditions, and for token length 3 numbers, accuracy was higher on some cases than expected, with the numeric-length effect being confounded by sampling range.
Limitations
- Most results from a single model (Claude Haiku) due to budget constraints; deceptive and frequency analyses not run across all models.
- Token length and frequency effects are confounded by sampling constraints and cannot be fully separated.
- Evaluation uses only formal set-operation prompts with a fixed temperature and accuracy metric without partial credit.
Experimental setup
Datasets: NLTK Wordlist corpus Google Books Ngram corpus WordNet
Benchmarks: SetLexSem Challenge
Metrics: accuracy standard deviation of accuracy
Baselines: Claude Instant Claude Haiku Claude Sonnet Mistral Large Mistral Small LLaMa 3 70b
Builds on: chain-of-thought prompting WordNet NLTK word list
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