Top-down influences on crowding: The word superiority effect and attentional cuing
Dannemiller, James L.
Doctor of Philosophy
The goal of the current studies was to examine the influence of top-down mechanisms on the crowding effect. Crowding refers to the reduced ability to identify an object, typically a letter, when other objects in the periphery surround it spatially. We used crowding as a tool to examine the semantic contribution to word superiority effect and investigate the role that attentional cuing plays in both the crowding effect and the word superiority effect. In Experiments 2 and 3, we used a secondary task of either a lexical decision task or an additional letter identification task to assess priming from related crowded items, and found that semantics do not play a role in the word superiority effect. By controlling for letter sequence familiarity we found that words and pronounceable non-words produced comparable priming effects, suggesting that the word superiority effect results from pattern familiarity. In Experiments 4 and 5, we examined whether attentional cuing of crowded stimuli produces target enhancement, distracter suppression effects, or both. We found that neither endogenous nor exogenous cues produced distracter suppressions effects, but there was evidence for signal enhancement effects especially with word stimuli. The evidence suggests that exogenously and endogenously orienting attention interact with the word superiority effect such that they enhance the effect of context for words, but do so in different ways.