# Ablation study and multi-task heads

Source: https://onco.cc/terms/ablation-study/  
OnCo record `ablation-study` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

An ablation removes one component or modality at a time and re-measures performance, which is the only way to know what each part contributes; multi-task heads let one shared backbone serve several outputs.

## Summary

In machine learning, ablation is the removal of a component to determine its contribution to the system (Wikipedia). For a multimodal cancer model the ablation is per modality: drop mutations, copy number, protein or the pretrained encoder and see whether survival or drug-response accuracy moves. Multi-task learning solves several tasks at once through a shared representation with task-specific heads (Wikipedia), which is efficient but can let one easy task (cancer type) dominate the backbone.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: ablation study; ablation studies; ablation; leave-one-modality-out; multi-task learning; multi-task heads; task heads; specialised task heads; shared backbone
- Tags: cansim-terms

## Notes

- Listed in the CanSim terms map 1.0.0 (docs/onco/terms.json, generated 2026-09-24), CC BY 4.0, attribution: CanSim project, an open, public-data-first cancer foundation-model programme; CanSim page path /terms/ablation-study.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Ablation_(artificial_intelligence)
- Wikipedia: multi-task learning: https://en.wikipedia.org/wiki/Multi-task_learning
- Wikipedia: https://en.wikipedia.org/wiki/Ablation_(artificial_intelligence)

## Connected records

- terms: [Accuracy, macro-F1 and confusion matrices](https://onco.cc/terms/accuracy-f1/), [Cancer AI vocabulary (CanSim terms map)](https://onco.cc/terms/cancer-ai-vocabulary/), [Mechanism-of-action recovery and known-biology probes](https://onco.cc/terms/mechanism-of-action-recovery/), [Multimodal fusion (early, late, modality dropout)](https://onco.cc/terms/multimodal-fusion/)

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