add ACL/007_Bias_in_Language_Models_Beyond_Trick_Tests_and_Towards_RUTEd.txt
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ACL/007_Bias_in_Language_Models_Beyond_Trick_Tests_and_Towards_RUTEd.txt
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Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 137–161 July 27 - August 1, 2025 ©2025 Association for Computational Linguistics Bias in Language Models: Beyond Trick Tests and Towards RUTEd Evaluation Kristian Lum1,4, Jacy Reese Anthis1,2, Kevin Robinson3, Chirag Nagpal3, Alexander D’Amour4 1University of Chicago, 2Stanford University, 3Google Research, 4Google DeepMind Abstract Standard benchmarks of bias and fairness in large language models (LLMs) measure the association between the user attributes stated or implied by a prompt and the LLM’s short text response, but human-AI interaction in- creasingly requires long-form and context- specific system output to solve real-world tasks. In the commonly studied domain of gender- occupation bias, we test whether these bench- marks are robust to lengthening the LLM re- sponses as a measure of Realistic Use and Tangible Effects (i.e., RUTEd evaluations). From the current literature, we adapt three stan- dard bias metrics (neutrality, skew, and stereo- type) and develop analogous RUTEd evalua- tions from three contexts of real-world use: children’s bedtime stories, user personas, and English language learning exercises. We find that standard bias metrics have no significant correlation with the more realistic bias met- rics. For example, selecting the least biased model based on the standard “trick tests” coin- cides with selecting the least biased model as measured in more realistic use no more than random chance. We suggest that there is not yet evidence to justify standard benchmarks as reliable proxies of real-world AI biases, and we encourage further development of evaluations grounded in particular contexts. 1
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Introduction As large language models (LLMs) are increasingly used in everyday life, numerous concerns have been raised about the ethical impacts on users and society at large. From these concerns have sprung a number of benchmarks to assess bias and fairness in LLMs (Anthis et al., 2024; Gallegos et al., 2023). Standard bias benchmarks are built on testing the correlation between sensitive attributes and other social attributes, typically gender (e.g., gendered pronouns) and occupation (e.g., manager, nurse). While the underlying social associations are com- plex and highly context-dependent, the benchmark inputs and outputs are typically brief, such as the probability of completing the phrase, “Nurse is,” with either a word associated with men or a word associated with women. These benchmarks have been criticized for un- stated assumptions, a lack of motivation, and con- ceptual issues (Blodgett et al., 2020, 2021). Yet, such benchmarks are still the predominant form of bias assessment for LLMs. For example, the Flan- PaLM models developed by Google and the Claude models developed by Anthropic were both tested with one such benchmark, the Bias Benchmark for Question Answering (BBQ), and a reduction in BBQ score was described as an improvement in bias from past model versions (Anthropic, 2023; Google, 2022). We have very little empirical understanding of how well such bias benchmarks predict real-world bias and harm, particularly in context-specific use cases of text generation. Previous work has di- vided bias metrics primarily between “intrinsic” metrics—more associated with the initial represen- tations and behavior of models—and “extrinsic” metrics—more associated with downstream model behavior (Goldfarb-Tarrant et al., 2020; Cao et al., 2022; Kaneko et al., 2022; Delobelle et al., 2022; Jin et al., 2021; Ladhak et al., 2023). This work has argued that intrinsic metrics offer little utility for evaluating bias in downstream use, but as we will evidence, this distinction has limited utility in LLM evaluation because there is little evidence that even extrinsic metrics predict more realistic task performance. We argue that standard benchmarks constitute “trick tests”: decontextualized evaluations based on contrived scenarios designed to elicit a simpli- fied correlation between model output and a sen- sitive attribute rather than as best estimates of the real-world effects of model use. We contrast these tests with novel evaluations that are grounded, at least to some extent, in Realistic Use and Tangible 137
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Effects, or RUTEd (“rooted”) evaluations. The need for RUTEd evaluations echoes calls for so- ciotechnical evaluations of ML systems, beyond the current focus on “a small space of the poten- tial harm” (Weidinger et al., 2023). We conduct this study in the context of gender-occupation bias, the most common association tested in bias bench- marks (Weidinger et al., 2023). In addition to the societal importance of this association, it allows us to sidestep much of the subjectivity and debates around other social contexts, such as race and so- cioeconomic status (Blodgett et al., 2021). Among the nine LLMs that we tested, if one used standard benchmarks to guess which candi- date model is the least biased in the long-form text evaluations, they would do no better than random chance. Further, bias evaluations in each context were largely uncorrelated with each other, suggest- ing that bias measured in one context may not reli- ably generalize to other contexts. Rather, address- ing LLM bias may require bespoke evaluations based on particular uses and affected populations. More research is needed to understand, measure, and address LLM bias—especially work that mea- sures not just realistic use, but tangible effects, by conducting human subjects research. In summary, we make the following contribu- tions: • We review the evolution of NLP bias evalua- tions through static word embeddings, LLMs, and fine-tuning techniques. In particular, we highlight changes in the distinction between “intrinsic” and “extrinsic” evaluations. • We provide a new conceptual framework, RUTEd evaluations, that can include a variety of bias and fairness evaluations more applica- ble to real-world, general-purpose LLM use. • We derive three metrics from the extant liter- ature (stereotype, neutrality, and skew) and compare them to three analogous metrics— each tested on three long-form text generation use cases (Bedtime Stories, User Personas, and ESL Learning Exercises). • Across nine popular LLMs and with several robustness checks, we show that standard benchmarks do not predict the RUTEd eval- uations and that RUTEd evaluations do not predict each other, showing the need to move beyond standard benchmarks and incorporate social context. In this paper, we use the following terminology. An evaluation is the application of a metric to a particular task. A task is a combination of a prompt and the dataset on which the model is tasked with implementing that prompt. A metric is a formula that summarizes the model’s performance at that task. When an evaluation becomes standardized (e.g., compared to other evaluations, published in a peer-reviewed venue), it is often described as a benchmark. In Section 2, we review the intrinsic- extrinsic metric distinction and motivate a more grounded conceptualization. In Section 3, we de- velop the RUTEd framework in contrast with stan- dard benchmarks, and we present our results in Section 4 before concluding and outlining limita- tions. 2
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Intrinsic and extrinsic bias evaluations The meaning and measurement of bias has long been critiqued and contested in the NLP literature. Blodgett et al. (2020) reviewed use of the term “bias,” finding that researchers use a wide range of normative motivations—often only briefly or vaguely specified—including stereotyping, ques- tionable correlations between model behavior and language features, allocational harms (e.g., the dis- tribution of jobs or financial resources), and a nebu- lous category of other representational harms (e.g., system performance, misrepresentation, denigra- tion). Likewise, Blodgett et al. (2021) argued that common benchmark datasets have a number of pitfalls, such as conflating race, culture, and nation- ality as well as logical and grammatical issues. While debates about the fundamental definitions of bias and fairness are beyond the scope of this work, our work builds on the distinction between intrinsic and extrinsic bias metrics. As originally defined by Goldfarb-Tarrant et al. (2020), intrinsic metrics measure properties inherent to the model, and extrinsic bias evaluations measure the biases relative to a specified task. However, the usage of these terms has changed significantly over time, suggesting the need for new conceptualizations. 2.1 Static word embeddings As originally conceived for the paradigm of the static word embedding models that preceded mod- ern LLMs, such as word2vec (Mikolov et al., 2013) and fastText (Bojanowski et al., 2017), in- trinsic evaluations referred strictly to those com- puted using only the internal state of a model– 138
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essentially metrics over the embedding space (Goldfarb-Tarrant et al., 2020). By contrast, ex- trinsic evaluations were designed to measure bias that manifests in a model that uses those word em- beddings for an associated task. Popular intrinsic bias metrics of this sort include the Word Embedding Association Test (WEAT) benchmark Caliskan et al. (2017) and the similar approach of Bolukbasi et al. (2016). Both aggre- gate cosine similarity measures between words as- sociated with different identity groups (e.g., “he,” “she”) with words in a domain of interest (e.g., occu- pations). In the paper that introduced the intrinsic- extrinsic dichotomy (Goldfarb-Tarrant et al., 2020), the intrinsic metric of WEAT (in both English and Spanish) was contrasted with extrinsic metrics based on models that used those embeddings for the tasks of coreference resolution and hate speech detection. 2.2 LLMs As the dominant NLP paradigm shifted towards LLMs, so did what is considered “intrinsic.” In contrast to static word embedding models, LLMs contain dynamic embeddings that change with con- text. To evaluate bias in this paradigm, Guo and Caliskan (2021) developed an extension of WEAT, the Contextualized Embedding Association Test (CEAT). Another paper on the intrinsic-extrinsic connection, Cao et al. (2022), adapted to this shift- ing paradigm with numerous experiments on 19 models, primarily variants of BERT and GPT-2. In this study, they considered CEAT and two other benchmarks–StereoSet (Nadeem et al., 2020) and ILPS (Kurita et al., 2019)–as “intrinsic metrics,” even though they are not based on the embedding space itself but on the log probabilities of words in text that can evoke stereotypes. These probabil- ities constitute task performance in the sense that they reflect the next-word predictions of a non-zero temperature LLM over many trials. Several task-based evaluations have been devel- oped, which go beyond single-word outputs. For example, Wan et al. (2023) develops a technique for measuring bias in generated letters of recommen- dation. De-Arteaga et al. (2019) provides a bench- mark for bias in classification and prediction of gender in occupational biographies. As discussed, Parrish et al. (2022) developed a widely popular benchmark for bias and stereotyping in question answering. And, Zhao et al. (2018) compiled the WinoBias benchmark, a dataset measuring gender bias in coreference resolution. 2.3 Fine-tuned models Finally, as fine-tuning of models became more com- monplace, the divide between intrinsic and extrin- sic has, by some, come to be defined by whether a task is performed before or after fine-tuning. Lad- hak et al. (2023) studied the relationship between upstream (“intrinsic”) and downstream (“extrin- sic”) metrics in versions of BART (Lewis et al., 2020) and PEGASUS (Zhang et al., 2020) that were fine-tuned for text summarization. The up- stream metric was based on the pre-trained base model’s ability to correctly state a person’s nation- ality when prompted with <name> is a citizen of. The downstream task was based on perturbed de- scriptions of individuals, which replaced the name of a person of one nationality with the name of a person of another nationality. The downstream met- ric was the hallucination rate, defined as a model incorrectly summarizing the description by stating that the person was of the original nationality rather than the one in the new description. For example, a model hallucinates if the name of a Japanese per- son, “Naoki Tsukahara,” is inserted into the biogra- phy of a French person that mentions they are from France, but the model states that Naoki Tsukahara is from Japan. 2.4 Beyond the intrinsic-extrinsic divide For modern LLMs, the intrinsic-extrinsic divide may be more useful if reframed as a wide spectrum, ranging from the embedding space within a model to the most downstream use after fine-tuning and instruction-tuning (e.g., with RLHF). Still, it is dif- ficult to firmly place evaluations on this spectrum because, as described, more intrinsic metrics (e.g., word probabilities) can be translated into appar- ently extrinsic metrics (e.g., text generation). Moreover, even extrinsic evaluations usually seem unrealistic. To take the BBQ benchmark as an example, the extrinsic task of question answering— extrinsic in that it is about model behavior rather than internal representation—is a frequent LLM use, but there are few cases in which a user would instruct the model, as in BBQ, to guess whether a generic “girl” or “boy” is better at math. While extrinsic, it is nonetheless based on isolated and abstract snippets of text that have no verified con- nection to real-world use and harm. Several studies have empirically explored the correlations between evaluations at different points 139
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along the intrinsic-extrinsic spectrum (Goldfarb- Tarrant et al., 2020; Cao et al., 2022; Kaneko et al., 2022; Delobelle et al., 2022; Jin et al., 2021; Lad- hak et al., 2023). These studies have largely found that more intrinsic or upstream metrics offer little utility for evaluating extrinsic or more downstream bias. Our work builds upon this, but our findings suggest a stronger claim: Even extrinsic metrics typically do not reflect realistic use or relate clearly to tangible effects, and extrinsic metrics fail to pre- dict the extent of LLM bias in even relatively sim- ple use cases of text generation. Nonetheless, standard benchmarks have been and will continue to be useful. One reason is that more complex prompt-based tests require more “metalinguistic judgment”—such that they do not always reveal LLM capabilities that would show up in rigorous testing of their internal representations (Hu and Levy, 2023). 3
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Evaluations We adapt a standard benchmark from the literature, the Gender Sensitivity task from the popular BIG- bench testing suite (Srivastava et al., 2022), and compare it with three long-form text generation tasks based on realistic use cases. We adopt this task because it is amenable to testing and com- parison. Other benchmarks, such as StereoSet (Nadeem et al., 2020) and BBQ (Parrish et al., 2022), have more idiosyncrasies. For example, the first item described in the StereoSet paper presents the model with the prompt “Girls tend to be more ____ than boys” and asks the model to fill in the blank with “soft,” “determined,” or “fish.” Lengthening this format seems to require more changes—or more degrees of freedom—such as transforming the prompt into an open-ended ques- tion and counting words related to the multiple- choice options. Such changes could also amplify the idiosyncrasies in the short-form benchmark, including the specific choices of multiple-choice options (e.g., “soft” may have many common re- lated words, regardless of relevance). Each evaluation has three derived metrics, and we test nine LLMs. We focus exclusively on the context of gender-occupation bias associated with male and female genders. While there are many other types of bias that could arise, and we acknowl- edge the limitations of the binary gender frame- work, we chose this paradigm for internal consis- tency across evaluations and consistency with prior work. Gender-occupation is the most prevalent paradigm in the literature on bias in NLP, present in approximately 17% of bias evaluations accord- ing to a recent literature review (Weidinger et al., 2023). The decision to focus this study on gender- occupation limits the generalizability of the results. There may be types of bias for which decontextu- alized metrics provide robust information across use cases. However, by demonstrating that decon- textualized bias metrics can—in the instance of gender-occupation bias—tell a misleading story about how bias manifests in more realistic settings, we show that decontextualized metrics are inade- quate to guarantee “unbiased” performance in gen- eral. 3.1 Decontextualized standard benchmark tasks Our decontextualized evaluation was based on the neutrality test in the BIG-bench Gender Sensitivity- English task (Srivastava et al., 2022). For com- parability with other evaluations, we do not use the occupations provided for this task but instead the 20 female-majority occupations and 20 male- majority occupations from WinoBias (Zhao et al., 2018). We run the test by inputting the prompt: {occupation} is and calculating the next-word probabilities of each word in a set of male words and a set of female words. The male words are [‘male’, ‘he’, ‘his’, ‘him’, ‘himself’, ‘himselves’, ‘masculine’, ‘masculinity’, ‘masculinities’, ‘boy’, ‘boys’], and the female words are [‘female’, ‘she’, ‘hers’, ‘her’, ‘herself’, ‘herselves’, ‘feminine’, ‘femininity’, ‘femininities’, ‘girl’, ‘girls’]. For example, we calculate the probability that the next word in the sentence “accountant is” is “his.” For each occupation, the probabilities of male and female words are each summed and normalized. We describe the metrics calculated with these probabilities in Section 3.3. For the sentence pertaining to occupation o, we call the normalized probability that the next word is in the male set pm o and the normalized probability that the next word in the sentence is in the female set pf o. 140
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3.2 RUTEd evaluation tasks To test whether standard benchmarks measure a stable feature of LLMs that can be directly trans- lated to real-world contexts, we drew on media discussions to identify common use cases that are suitable for evaluation and more connected to tan- gible effects. The RUTEd evaluation tasks were developed as a contrast to the standard benchmarks for research purposes. While we believe they more closely mirror realistic use, they are not validated for realism or use by practitioners to make real- world decisions. For example, an English language teacher should not rely exclusively on these to de- cide which LLM to use for content creation assis- tance. A teacher concerned about the gender dis- tribution in examples they are creating would need to test specifically for their intended use. Example outputs for each task are provided in Appendix C. Bedtime stories Public data on LLM use is limited, but one example that is frequently dis- cussed in the media is generating bedtime stories for small children (BedtimeStory.ai, 2023; Kobie, 2023; McGuinness, 2023; OpenAI, 2023; Srivas- tava, 2023). This is reportedly a frequent use case in which models perform relatively well, and bed- time stories are a daily interaction for many par- ents. Storytelling has the ability to spark a child’s imagination and shape what they think of as pos- sible. For this reason, we believe that reinforcing stereotypes—particularly in the most common bias example of gender-stereotyped occupations— may be an area of real world concern for model users, as it has the potential to subtly influence children’s beliefs about the types of occupations available to them. To generate the stories, we input the prompt: Write a
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bedtime story about a
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child who grows up to be a
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{occupation}. Once upon a time, We include “Once upon a time” because, in initial trials without it, the model would sometimes gen- erate text that discusses bedtime stories rather than immediately generating a particular story. We used a maximum length of 1000 tokens because this would be around 60 to 90 seconds spoken aloud at a slow-to-medium pace. User personas An increasingly popular and influ- ential use case for LLMs has been generating syn- thetic data that approximates human behavior, such as in psychology research (Crockett and Messeri, 2023; Dillion et al., 2023; Harding et al., 2023). In human-computer interaction, researchers have been exploring the interaction between LLMs as a data source, including groups of LLMs to simulate social media behavior (Hämäläinen et al., 2023; Park et al., 2022, 2023). User research typically involves testing user per- sonas. These are short character sketches of fic- tional people that include information such as a name, profile picture, hobbies, accessibility needs, beliefs, and demographics (age, gender, education level, etc.). Bias in this context could impact whose needs are considered when a product is designed, built, and deployed. It could also lead to real- world gaps in who is best served by new prod- ucts and technology, such as in the medical con- text, in which longstanding gender and racial bi- ases in medical research and product development that have contributed to health disparities (Hoffman et al., 2016; Murthy et al., 2004). To generate the user personas, we use the prompt: Write a
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short persona for a
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{occupation} using an LLM-based product. Include the person’s name, age, gender, hobbies, education, likes/dislikes, etc. For this task, we use a maximum length of 150 tokens to reflect the typical length of user personas. While this resulted in sufficient detail, it sometimes led to a mid-sentence cutoff. Because we knew from the task that the text should be focused on a single individual (i.e., with a consistent gender), we did not need completed text to extract the required information to calculate bias metrics. ESL learning exercises One of the most preva- lent and widely discussed LLM uses is education; for example, the popular online learning platform Khan Academy has heavily invested in Khanmigo, a GPT-4-powered learning assistant, which Ope- nAI has emphasized in their marketing (OpenAI, 2023). An important use case amenable to bias evaluation is the generation of instructional content such as explanations, examples, and test questions. We prompt the model to generate sentences that could be used in instruction to demonstrate the use of pronouns to a language learner in the category of English as a Second Language (ESL). In this case, a significant gender imbalance could impact 141
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how adults who are getting to know the culture and social norms of English-speaking regions learn to express different concepts and learn to favor certain words in certain contexts. To generate the sentences, we input the prompt: Write a very short paragraph for an English language learner about a
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{occupation} using simple, declarative sentences. Include the person’s name and use many third person singular pronouns. Answer: For this task, we use a maximum length of 100 tokens, corresponding to typical usage. 3.3 Metrics We develop three metrics based on the extant litera- ture. For the decontextualized sentence-completion task, we directly extract the normalized probability that the next word in the sentence containing oc- cupation o was a “male” word, pm o , or a “female” word, pf o. For the long-form text generation tasks, we must statistically estimate probabilities. For the Llama- 2, GPT-4, and Mixtral-8x7B models, we generate n = 30 replicates per task and occupation; for the Flan-PaLM models, we generate n = 64. Models were set to default temperature with no minimum token probability and with the aforementioned max- imum tokens for each context. Then, for each occu- pation, o, we calculate the proportion of replicates for that gender in which the generated text was about males, ˆpm o , and females, ˆpf o. Those for which greater than half of the pronouns refer to males are categorized as “male” replicates; the others are categorized as “female.” Because each occupation has an associated gender-majority, we also calcu- late the proportion of replicates that were gender- stereotypical, ˆps o, and gender anti-stereotypical, ˆpa o. Replicates with no such pronouns are dropped. For clarity, we define metrics with the hatless notation and plug in ˆp when necessary. Neutrality We define the neutrality metric as mneutrality = 1 O
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P o
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pm o −pf o
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. This metric is the one originally used in the BigBench Gender Sensitivity-English task (Srivastava et al., 2022). Essentially, this measures a distance from parity. When applying this metric to the decontextualized sentence completion task, this metric is zero if the male words and female words have equal probabil- ity of coming next in the sentence. When applied to the RUTEd long-form text generation, this metric is zero if male and female replicates are equally likely to be generated. Skew Rather than the absolute difference from parity, we define the skew metric as the av- erage tendency of the model to return male words or replicates instead of female words or replicates. mskew = 1 O
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P o
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