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Improving Neural Additive Models with Bayesian Principles
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Applies a linearized Laplace approximation with block-diagonal Kronecker-factored GGN to neural additive models, yielding per-feature credible intervals, marginal-likelihood-based feature selection, and MI-based pairwise interaction selection (LA-NAM).
Problem
Neural additive models are interpretable but lack calibrated uncertainty, principled feature selection, and mechanisms for detecting feature interactions.
Approach
Treat each feature network as an independent block in a linearized Laplace posterior so that predictive variance decomposes additively per feature, use the lower bound on the log-marginal likelihood with per-network precisions as ARD for implicit feature selection, and rank feature pairs by posterior mutual information from a last-layer Laplace approximation to add joint feature networks.
Key results
- On MIMIC-III ICU mortality, LA-NAM achieves 79.6 AUROC and 0.264 NLL versus NAM's 77.6 AUROC and 0.274 NLL; with 10 selected interactions LA-NAM reaches 80.2 AUROC, close to LightGBM's 80.6.
- On HiRID, LA-NAM improves NLL to 0.174 from NAM's 0.228 with comparable AUPRC.
- On MIMIC-III, LA-NAM reduces ECE from 0.019 (NAM) to 0.009.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| replace NAM with Laplace-approximated inference | NAM · MIMIC-III ICU Mortality | AUROC: 77.6 ± 0.03 -> 79.6 ± 0.01 | Helped |
| replace NAM with Laplace-approximated inference | NAM · MIMIC-III ICU Mortality | NLL: 0.274 ± 8e-5 -> 0.264 ± 5e-5 | Helped |
| replace NAM with Laplace-approximated inference | NAM · HiRID ICU Mortality | AUROC: 89.6 ± 0.17 -> 90.1 ± 0.03 | Helped |
| add 10 selected feature interactions (ablation) | LA-NAM · MIMIC-III ICU Mortality | AUROC: 79.6 ± 0.01 -> 80.2 ± 0.10 | Helped |
| add 10 selected feature interactions (ablation) | LA-NAM · MIMIC-III ICU Mortality | NLL: 0.264 ± 5e-5 -> 0.262 ± 3e-4 | Helped |
| add 10 selected feature interactions (ablation) | LA-NAM · HiRID ICU Mortality | AUROC: 90.1 ± 0.03 -> 90.1 ± 0.01 | No clear effect |
| add 10 selected feature interactions (ablation) | LA-NAM · HiRID ICU Mortality | ECE: 0.009 ±3.3e-4 -> 0.011 ±4.9e-4 | Hurt |
| use a shallow 64-unit ReLU feature network (ablation) | NAM · MIMIC-III ICU Mortality | AUROC: 78.89 (±0.04) -> 79.02 (±0.02) | No clear effect |
| replace ReLU with GELU in a shallow 64-unit feature network (ablation) | NAM · MIMIC-III ICU Mortality | AUROC: 79.02 (±0.02) -> 77.54 (±0.02) | Hurt |
| add Laplace-approximated Bayesian inference to the 64-unit GELU NAM (ablation) | NAM (64, GELU) · MIMIC-III ICU Mortality | AUROC: 77.54 (±0.02) -> 79.58 (±0.01) | Helped |
| use Laplace-approximated inference instead of NAM | NAM · MIMIC-III ICU Mortality | ECE: 0.019 ±3.7e-4 -> 0.009 ±1.6e-4 | Helped |
| remove the anion-gap feature network (ablation) | LA-NAM · MIMIC-III ICU Mortality | feature attribution | Mixed |
Surprising findings
- Plain ReLU NAM with GELU-activated feature networks performs worse, and the paper notes that NAM ensembles of ReLU/GELU networks collapse in function-space diversity.
- OAK-GP with all pairwise interactions (OAK-GP*) degrades substantially on MIMIC-III (AUROC 71.7 vs 79.9 first-order).
Limitations
- Interaction selection is restricted to second order because the search space grows exponentially for higher orders.
- Laplace approximation assumes block-diagonal (feature-independent) posterior, and the true posterior may have strong dependencies between feature networks, which the method only partly addresses via a last-layer approximation.
- MIMIC-III preprocessing relied on a pre-processed dataset provided by the authors of prior work; medical plausibility checks rely on personal communication with experts.
Experimental setup
Datasets: UCI regression benchmarks UCI classification benchmarks MIMIC-III HiRID synthetic additive regression dataset
Benchmarks: UCI regression UCI classification MIMIC-III ICU mortality HiRID ICU mortality
Metrics: negative log-likelihood AUROC AUPRC ECE root Brier score SKCE quantile calibration error
Baselines: NAM GAM OAK-GP LightGBM EBM deep ensembles MC-Dropout
Builds on: neural additive models linearized Laplace approximation KFAC-GGN automatic relevance determination
Closest papers by meaning
- Neural Additive Models: Interpretable Machine Learning with Neural Nets (NeurIPS 2021 · similarity 0.88)
- Projected Neural Additive Models as Universal Approximators (NeurIPS 2026 · similarity 0.86)
- Gaussian Process Neural Additive Models (AAAI 2024 · similarity 0.85)
- Do Bayesian Neural Networks Actually Behave Like Bayesian Models? (ICML 2025 · similarity 0.82)
- Bayesian Neural Scaling Law Extrapolation with Prior-Data Fitted Networks (ICML 2025 · similarity 0.82)
- Make Me a BNN: A Simple Strategy for Estimating Bayesian Uncertainty from Pre-trained Models (CVPR 2024 · similarity 0.82)
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