Visual objects are often defined by multiple features. Therefore, learning novel objects entails learning feature conjunctions. Visual cortex is organized into distinct anatomical compartments, each of which is devoted to processing a single feature. A prime example are neurons purely selective to color and orientation, respectively. However, neurons that jointly encode multiple features (mixed selectivity) also exist across the brain and play critical roles in a multitude of tasks. Here, we sought to uncover the optimal policy that our brain adapts to achieve conjunction learning using these available resources. 59 human subjects practiced orientation-color conjunction learning in four psychophysical experiments designed to nudge the visual system towards using one or the other resource. We find that conjunction learning is possible by linear mixing of pure color and orientation information, but that more and faster learning takes place when both pure and mixed selectivity representations are involved. We also find that learning with mixed selectivity confers advantages in performing an untrained “exclusive or” (XOR) task several months after learning the original conjunction task. This study sheds light on possible mechanisms underlying conjunction learning and highlights the importance of learning by mixed selectivity.

视觉对象通常由多个特征定义。因此，学习新事物需要学习特征连词。视觉皮层被组织成不同的解剖区，每个区都专门处理单个特征。一个典型的例子是神经元分别对颜色和方向具有纯粹的选择性。然而，联合编码多种特征（混合选择性）的神经元也存在于大脑中，并在多种任务中发挥关键作用。在这里，我们试图揭示我们的大脑利用这些可用资源实现联合学习的最佳策略。 59 名人类受试者在四项心理物理学实验中练习了方向-颜色结合学习，这些实验旨在推动视觉系统使用一种或另一种资源。我们发现，通过纯颜色和方向信息的线性混合可以实现联合学习，但是当涉及纯选择性表示和混合选择性表示时，会发生更多更快的学习。我们还发现，在学习原始连接任务几个月后，混合选择性学习在执行未经训练的“异或”（XOR）任务方面具有优势。这项研究揭示了联合学习的可能机制，并强调了混合选择性学习的重要性。