A company fine-tunes a model using Vertex AI and notices the model's performance drops on the original training task (e.g., language understanding) after fine-tuning for a new task (e.g., summarization). What could be the cause?
Fine-tuning on a narrow task can overwrite general knowledge, leading to performance degradation on the original task.
Why this answer
Catastrophic forgetting occurs when a neural network loses previously learned knowledge upon being fine-tuned on a new task. In this scenario, fine-tuning the model for summarization overwrites the weights responsible for language understanding, causing performance degradation on the original task. This is a well-known limitation of sequential fine-tuning in deep learning.
Exam trap
Google Cloud often tests the distinction between catastrophic forgetting and underfitting, as candidates may mistakenly think the model simply didn't learn the new task well, rather than recognizing that it forgot the original task due to weight overwriting.
How to eliminate wrong answers
Option A is wrong because data leakage refers to the inadvertent exposure of target information during training, which would typically inflate performance metrics rather than cause a drop on the original task. Option B is wrong because model quantization reduces numerical precision (e.g., from FP32 to INT8) to improve inference speed and memory efficiency, but it does not inherently cause performance loss on a previously learned task; any accuracy loss from quantization is generally uniform across tasks. Option D is wrong because underfitting means the model fails to capture patterns in the training data, resulting in poor performance on both the original and new tasks, not a selective drop on the original task after fine-tuning.