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P. Altmeyer

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We focus on explainability as a desideratum for automated decision-making systems, rather than only models. Although the explainable artificial intelligence (XAI) paradigm offers an impressive variety of solutions to increase the transparency of automated decisions, XAI contributions rarely account for the complete systems—social and institutional environments—where models operate. Our work focuses on one such system in the domain of social welfare, which increasingly turns to automated decision-making to carry out targeted digital surveillance. Specifically, we present a case study of a black-box machine learning model previously used in a major Dutch city to support its officials in the task of detecting fraud. Employing analyses established in the field of system safety, we identify five types of hazards that could have occurred after the introduction of the model. For each of them, we reason about the potential value of XAI interventions as hazard mitigation strategies. The case study illustrates how the deployment of models may impact processes that exist far upstream and downstream from their decision logic, making explainability and/or interpretability insufficient to guarantee the systems’ safe operation. In many cases, XAI techniques may only be able to reasonably address a small fraction of hazards related to the use of algorithms; several major hazards that we identify would have still posed risks if the system had relied on an interpretable model. Thus, we empirically demonstrate that the values, which lie at the heart of XAI research, such as responsibility, safety, or transparency, ultimately necessitate a broader outlook on automated decision-making systems. ...
Doctoral thesis (2026) - P. Altmeyer, C.C.S. Liem, A. van Deursen
Many of the most celebrated recent advances in artificial intelligence (AI) have been built on the back of highly complex and opaque models that need little human oversight to achieve strong predictive performance. But while their capacity to recognize patterns from raw data is impressive, their decision-making process is neither robust nor well understood. This has so far inhibited trust and widespread adoption of these technologies. This thesis contributes to research efforts aimed at tackling these challenges, through interdisciplinary insights and methodological contributions.

The principle goal of this work is to contribute methods that help us in making opaque AI models more trustworthy. Specifically, we aim to (1) explore and challenge existing technologies and paradigms in the field; (2) improve our ability to hold opaque models accountable through thorough scrutiny; and, (3) leverage the results of such scrutiny during training to improve the trustworthiness of models. Methodologically, the thesis focuses on counterfactual explanations and algorithmic recourse for individuals subjected to opaque AI systems. We explore what type of real-world dynamics can be expected to play out when recourse is provided and implemented in practice. Based on our finding that individual cost minimization–a core objective in recourse–neglects hidden external costs of recourse itself, we revisit yet another established objective: namely, that explanations should be plausible first and foremost. Our work demonstrates that a narrow focus on this objective can mislead us into trusting fundamentally untrustworthy systems. To avoid this scenario, we propose a novel method that aids us in disclosing explanations that are maximally faithful, that is consistent with the behavior of models. This not only allows us to assess the trustworthiness of models, but also improve it: we show that faithful explanations can be used during training to ensure that models learn plausible explanations.

Finally, we also critically assess efforts towards trustworthy AI in the context of modern large language models (LLM). Specifically, we cast doubt on recent findings and practices presented in the field of mechanistic interpretability and caution our fellow researchers in this space against misinterpreting and inflating their findings.

In summary, this thesis makes cutting-edge research contributions that improve our ability to make opaque AI models more trustworthy. Beyond our core research contributions, this thesis makes substantial contributions to open-source software. Through various software packages that we have developed, we make our research and that of others more accessible.
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Conference paper (2025) - Karol Dobiczek, P. Altmeyer, C.C.S. Liem
The use of large language model (LLM) classifiers in finance and other high-stakes domains calls for a high level of trustworthiness and explainability. We focus on counterfactual explanations (CE), a form of explainable AI that explains a model’s output by proposing an alternative to the original input that changes the classification. We use three types of CE generators for LLM classifiers and assess the quality of their explanations on a recent dataset consisting of central bank communications. We compare the generators using a selection of quantitative and qualitative metrics. Our findings suggest that non-expert and expert evaluators prefer CE methods that apply minimal changes; however, the methods we analyze might not handle the domain-specific vocabulary well enough to generate plausible explanations. We discuss shortcomings in the choice of evaluation metrics in the literature on text CE generators and propose refined definitions of the fluency and plausibility qualitative metrics. ...
Developments in the field of Artificial Intelligence (AI), and particularly large language models (LLMs), have created a 'perfect storm' for observing 'sparks' of Artificial General Intelligence (AGI) that are spurious. Like simpler models, LLMs distill meaningful representations in their latent embeddings that have been shown to correlate with external variables. Nonetheless, the correlation of such representations has often been linked to human-like intelligence in the latter but not the former. We probe models of varying complexity including random projections, matrix decompositions, deep autoencoders and transformers: all of them successfully distill information that can be used to predict latent or external variables and yet none of them have previously been linked to AGI. We argue and empirically demonstrate that the finding of meaningful patterns in latent spaces of models cannot be seen as evidence in favor of AGI. Additionally, we review literature from the social sciences that shows that humans are prone to seek such patterns and anthropomorphize. We conclude that both the methodological setup and common public image of AI are ideal for the misinterpretation that correlations between model representations and some variables of interest are 'caused' by the model's understanding of underlying 'ground truth' relationships. We, therefore, call for the academic community to exercise extra caution, and to be keenly aware of principles of academic integrity, in interpreting and communicating about AI research outcomes. ...
Journal article (2024) - Patrick Altmeyer, Mojtaba Farmanbar, Arie van Deursen, Cynthia C.S. Liem
Counterfactual explanations offer an intuitive and straightforward way to explain black-box models and offer algorithmic recourse to individuals. To address the need for plausible explanations, existing work has primarily relied on surrogate models to learn how the input data is distributed. This effectively reallocates the task of learning realistic explanations for the data from the model itself to the surrogate. Consequently, the generated explanations may seem plausible to humans but need not necessarily describe the behaviour of the black-box model faithfully. We formalize this notion of faithfulness through the introduction of a tailored evaluation metric and propose a novel algorithmic framework for generating Energy-Constrained Conformal Counterfactuals that are only as plausible as the model permits. Through extensive empirical studies, we demonstrate that ECCCo reconciles the need for faithfulness and plausibility. In particular, we show that for models with gradient access, it is possible to achieve state-of-the-art performance without the need for surrogate models. To do so, our framework relies solely on properties defining the black-box model itself by leveraging recent advances in energy-based modelling and conformal prediction. To our knowledge, this is the first venture in this direction for generating faithful counterfactual explanations. Thus, we anticipate that ECCCo can serve as a baseline for future research. We believe that our work opens avenues for researchers and practitioners seeking tools to better distinguish trustworthy from unreliable models. ...
Existing work on Counterfactual Explanations (CE) and Algorithmic Recourse (AR) has largely focused on single individuals in a static environment: given some estimated model, the goal is to find valid counterfactuals for an individual instance that fulfill various desiderata. The ability of such counterfactuals to handle dynamics like data and model drift remains a largely unexplored research challenge. There has also been surprisingly little work on the related question of how the actual implementation of recourse by one individual may affect other individuals. Through this work, we aim to close that gap. We first show that many of the existing methodologies can be collectively described by a generalized framework. We then argue that the existing framework does not account for a hidden external cost of recourse, that only reveals itself when studying the endogenous dynamics of recourse at the group level. Through simulation experiments involving various state-of-the-art counterfactual generators and several benchmark datasets, we generate large numbers of counterfactuals and study the resulting domain and model shifts. We find that the induced shifts are substantial enough to likely impede the applicability of Algorithmic Recourse in some situations. Fortunately, we find various strategies to mitigate these concerns. Our simulation framework for studying recourse dynamics is fast and open-sourced. ...
Conference paper (2023) - P. Altmeyer, C.C.S. Liem, A. van Deursen
We present CounterfactualExplanations.jl: a package for generating Counterfactual Explanations (CE) and Algorithmic Recourse (AR) for black-box models in Julia. CE explain how inputs into a model need to change to yield specific model predictions. Explanations that involve realistic and actionable changes can be used to provide AR: a set of proposed actions for individuals to change an undesirable outcome for the better. In this article, we discuss the usefulness of CE for Explainable Artificial Intelligence and demonstrate the functionality of our package. The package is straightforward to use and designed with a focus on customization and extensibility. We envision it to one day be the go-to place for explaining arbitrary predictive models in Julia through a diverse suite of counterfactual generators. ...