Philosophy, Psychology and Neuroscience

The mystery of the missing letter: a new experimental paradigm reveals a novel visual effect in identity crowding

Is attention to some item necessary for consciousness of that item? Recently, work on this question has turned to the phenomenon of crowding: when an item is placed in peripheral vision, it is harder to identify when it is flanked by two other different items (this is ‘standard crowding’). The focus has been to a special case of crowding: identity crowding. In this case, the target item and the flanking items are the same in appearance. Some have claimed that identity crowding presents an example where subjects are conscious of some item, but are unable to attend to it. In this paper, I explain some methodological problems that have beset these debates. I then describe some recent experiments that circumvent this issue. This work reveals a new visual effect, which I call redundancy masking. I draw out three important consequences of this effect. First, it demonstrates a difference between standard crowding and identity crowding that is important for visual psychology. Second, it has important upshots for debates in philosophy and psychology over the relationship of attention to consciousness. Third, it raises important questions about the phenomenology of peripheral vision.