How does practice improve performance on vernier acuity tasks?

Practice improves performance on vernier acuity tasks—a type of hyperacuity—through changes in the visual cortex that allow the brain to discern line displacements smaller than the diameter of a single photoreceptor.1

Improvements occur through several mechanisms:

• Neural Representation: Practice can increase the number of neurons responding to a stimulus, enhancing the statistical reliability of decisions.1
• Tuning Functions: Learning may sharpen neuronal tuning, narrowing the range of stimulus attributes to which neurons respond and reducing overlap between neighboring neurons.1
• Reweighting: Improvements may result from changes in the strength of connections between sensory representations and higher-level brain areas.1

Training in vernier acuity is often highly specific, meaning improvements may not transfer across different orientations, visual fields, or eyes. While the process is more gradual without it, explicit accuracy feedback is not strictly required for this learning to occur. These gains are typically long-lasting, with performance improvements maintained for weeks or months after training.1