When you’re learning something new, you don’t just step randomly—you look for the path that gets you downhill fastest. Amari explains that many machine-learning models live on curved spaces, so the usual gradient doesn’t actually point straight “down.” The fix is the natural gradient, which adjusts each step to the true shape of the space so updates follow the steepest descent where it really matters. In simple terms, the algorithm stops slipping sideways and starts moving directly toward better settings. This idea originates from information geometry and applies to perceptrons, mixing-matrix problems such as blind source separation, and even linear dynamical systems used for deconvolution, not just toy examples.

Why care? Because using the natural gradient in online learning (updating as each new example arrives) can be as accurate, in the long run, as training with all data at once. Statistically, Amari shows this reaches “Fisher efficiency,” which means the online method eventually matches the gold-standard batch estimator instead of settling for second best. For everyday intuition, think of studying a little every day and still getting the same score as if you’d crammed with the full textbook—provided you study in the smartest direction.

This smarter direction can also dodge the annoying “plateaus” that slow standard backprop training, where progress feels stuck even though you’re doing everything “right.” By respecting the curvature of the model’s parameter space, natural-gradient steps help the learner escape these flat regions more readily, speeding up practical training of neural networks. Amari highlights this benefit while positioning the method across common tasks, from multilayer perceptrons to separating mixed signals, such as voices in a room or unmixing time-smeared audio.

There’s also a tip for tuning your learning rate without guesswork. The paper proposes an adaptive rule that makes big steps when you’re far from the goal and smaller steps as you get close, helping you converge quickly without overshooting. It’s like running on open ground but slowing near the finish line to avoid slipping past it. This adaptive schedule aligns naturally with the natural gradient, offering a practical approach that can be applied in real-world training loops.

Reference:
Amari, S. (1998). Natural Gradient Works Efficiently in Learning. Neural Computation, 10(2), 251–276. https://doi.org/10.1162/089976698300017746