Beyond Categorical Label Representations for Image Classification
This work addresses the robustness and data efficiency of image classifiers, offering a novel perspective on label design that could impact machine learning practitioners.
The paper tackles the problem of label representation in image classification by showing that using high-dimensional, high-entropy labels like audio spectrograms instead of traditional categorical labels leads to models with comparable accuracy but greater robustness to adversarial attacks and better performance with limited data.
We find that the way we choose to represent data labels can have a profound effect on the quality of trained models. For example, training an image classifier to regress audio labels rather than traditional categorical probabilities produces a more reliable classification. This result is surprising, considering that audio labels are more complex than simpler numerical probabilities or text. We hypothesize that high dimensional, high entropy label representations are generally more useful because they provide a stronger error signal. We support this hypothesis with evidence from various label representations including constant matrices, spectrograms, shuffled spectrograms, Gaussian mixtures, and uniform random matrices of various dimensionalities. Our experiments reveal that high dimensional, high entropy labels achieve comparable accuracy to text (categorical) labels on the standard image classification task, but features learned through our label representations exhibit more robustness under various adversarial attacks and better effectiveness with a limited amount of training data. These results suggest that label representation may play a more important role than previously thought. The project website is at \url{https://www.creativemachineslab.com/label-representation.html}.