Category learning can alter perception and its neural correlates

Learned Categorical Perception (CP) occurs when the members of different categories come to look more dissimilar (“between-category separation”) and/or members of the same category come to look more similar (“within-category compression”) after a new category has been learned. To measure learned CP and its physiological correlates we compared dissimilarity judgments and Event Related Potentials (ERPs) before and after learning to sort multi-featured visual textures into two categories by trial and error with corrective feedback. With the same number of training trials and feedback, about half the subjects succeeded in learning the categories (“Learners”: criterion 80% accuracy) and the rest did not (“Non-Learners”). At both lower and higher levels of difficulty, successful Learners showed significant between-category separation—and, to a lesser extent, within-category compression—in pairwise dissimilarity judgments after learning, compared to before; their late parietal ERP positivity (LPC, usually interpreted as decisional) also increased and their occipital N1 amplitude (usually interpreted as perceptual) decreased. LPC amplitude increased with response accuracy and N1 amplitude decreased with between-category separation for the Learners. Non-Learners showed no significant changes in dissimilarity judgments, LPC or N1, within or between categories. This is behavioral and physiological evidence that category learning can alter perception. We sketch a neural net model predictive of this effect.习得性类别知觉（Learned Categorical Perception, CP）指在习得新类别后，不同类别的刺激成员会愈发感知差异（即“类别间分离”），且抑或同一类别的刺激成员会愈发感知相似（即“类别内压缩”）的现象。为量化习得性类别知觉及其生理关联，本研究对比了被试在通过试错结合矫正反馈、将多特征视觉纹理分为两类前后的成对差异性判断结果与事件相关电位（Event Related Potentials, ERPs）。在训练次数与反馈频次一致的条件下，约半数被试成功掌握了类别分类任务（"习得组"：准确率达标阈值为80%），剩余被试则未完成学习任务（"未习得组"）。在不同难度层级下，与学习前相比，习得组在学习后的成对差异性判断中均表现出显著的类别间分离效应，且在一定程度上呈现出类别内压缩现象；其晚期顶叶ERP正成分（late parietal ERP positivity, LPC，通常被解读为与决策加工相关）的波幅显著升高，而枕叶N1波幅（通常被解读为与知觉加工相关）则显著降低。对于习得组而言，LPC波幅随反应准确率提升而增大，N1波幅则随类别间分离程度升高而减小。未习得组则未在类别内、类别间的差异性判断，以及LPC、N1指标上出现显著变化。上述结果为类别学习可改变知觉提供了行为与生理学层面的实证证据。本研究还构建了可预测该效应的神经网络模型。