School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Behavior and Mental Health, Peking University, Beijing, China.
J Vis. 2023 Aug 1;23(8):3. doi: 10.1167/jov.23.8.3.
Inner-outer asymmetry, where the outer flanker induces stronger crowding than the inner flanker, is a hallmark property of visual crowding. It is unclear the contribution of inner-outer asymmetry to the pattern of crowding errors (biased predominantly toward the flanker identities) and the role of training on crowding errors. In a typical radial crowding display, 20 observers were asked to report the orientation of a target Gabor (7.5° eccentricity) flanked by either an inner or outer Gabor along the horizontal meridian. The results showed that outer flanker conditions induced stronger crowding, accompanied by assimilative errors to the outer flanker for similar target/flanker elements. In contrast, the inner flanker condition exhibited weaker crowding, with no significant patterns of crowding errors. A population coding model showed that the flanker weights in the outer flanker condition were significantly higher than those in the inner flanker condition. Nine observers continued to train the outer flanker condition for four sessions. Training reduced inner-outer asymmetry and reduced flanker weights to the outer flanker. The learning effects were retained over 4 to 6 months. Individual differences in the appearance of crowding errors, the strength of inner-outer asymmetry, and the training effects were evident. Nevertheless, our findings indicate that different crowding mechanisms may be responsible for the asymmetric crowding effects induced by inner and outer flankers, with the outer flankers dominating the appearance more than the inner ones. Training reduces inner-outer asymmetry by reducing target/flanker confusion, and learning is persistent over months, suggesting that perceptual learning has the potential to improve visual performance by promoting neural plasticity.
内外不对称性，即外侧侧翼比内侧侧翼引起更强的拥挤效应，是视觉拥挤的一个显著特征。目前尚不清楚内外不对称性对拥挤错误模式（主要偏向于侧翼身份）的贡献，以及训练对拥挤错误的作用。在典型的放射状拥挤显示中，20 名观察者被要求报告目标 Gabor（7.5° 视轴外）的方位，该目标 Gabor 被水平子午线的内侧或外侧 Gabor 侧翼环绕。结果表明，外侧侧翼条件诱导出更强的拥挤效应，同时对外侧侧翼产生同化错误。相比之下，内侧侧翼条件表现出较弱的拥挤效应，没有明显的拥挤错误模式。群体编码模型表明，外侧侧翼条件中的侧翼权重明显高于内侧侧翼条件。九名观察者继续进行四个阶段的外侧侧翼条件训练。训练降低了内外不对称性，并降低了对外侧侧翼的权重。学习效果在 4 到 6 个月内保持不变。拥挤错误、内外不对称性强度以及训练效果的个体差异明显。然而，我们的发现表明，不同的拥挤机制可能负责内、外侧侧翼引起的不对称拥挤效应，外侧侧翼比内侧侧翼更主导外观。训练通过减少目标/侧翼混淆来降低内外不对称性，并且学习可以持续数月，这表明知觉学习有可能通过促进神经可塑性来提高视觉表现。
