What is new in perceptual learning?

What is new in perceptual learning? In the early days of research, specificity was the hallmark of perceptual learning; that is, improvements following training were limited to the trained stimulus features. For example, training with a stimulus improves performance for this stimulus but not for the same stimulus when rotated by 90° (Ball & Sekuler, 1987; Spang, Grimsen, Herzog, & Fahle, 2010). Because of this specificity, learning was thought to be mediated by neural changes at the early stages of vision. In the last decade, many procedures were discovered in which transfer occurs from trained to untrained conditions under certain conditions. The location of learning is now often thought to occur in higher stage of vision and decision-making. This special issue shows how the field has progressed along these lines.