We describe a patient LS, profoundly deaf in both ears from birth, with underdeveloped superior temporal gyri. Without hearing aids, LS displays no ability to detect sounds below a fixed threshold of 60 dBs, which classifies him as clinically deaf. Under these no-hearing-aid conditions, when presented with a forced-choice paradigm in which he is asked to consciously respond, he is unable to make above-chance judgments about the presence or location of sounds. However, he is able to make above-chance judgments about (...) the content of sounds presented to him under forced-choice conditions. We demonstrated that LS has faint sensations from auditory stimuli, but questionable awareness of auditory content. LS thus has a form of type-2 deaf hearing with respect to auditory content. As in the case of a subject with acquired deafness and deaf hearing reported on a previous occasion, LS’s condition of deaf hearing is akin in some respects to type-2 blindsight. As for the case of type 2 blindsight the case indicates that a form of conscious hearing can arise in the absence of a fully developed auditory cortex. (shrink)

The phenomenon of synesthesia has undergone an invigoration of research interest and empirical progress over the past decade. Studies investigating the cognitive mechanisms underlying synesthesia have yielded insight into neural processes behind such cognitive operations as attention, memory, spatial phenomenology and inter-modal processes. However, the structural and functional mechanisms underlying synesthesia still remain contentious and hypothetical. The first section of the present paper reviews recent research on grapheme-color synesthesia, one of the most common forms of synesthesia, and addresses the ongoing (...) debate concerning the role of selective attention in eliciting synesthetic experience. Drawing on conclusions of the first half, the paper’s second half examines the various models proposed to explain the cognitive mechanisms behind grapheme-color synesthesia, and discusses the explanatory virtues of a new model suggesting that grapheme-color synesthesia is grounded in memory. The last section offers an examination of some of the broader philosophical implications of synesthesia. (shrink)

Recent research on synesthesia has focused on how the condition may depend on selective attention, but there is a lack of consensus on whether selective attention is required to bind colors to their grapheme inducers. In the present study, we used a novel change detection paradigm to examine whether synesthetic colors guide the subject’s attention to the location of the inducer or whether selective attention is required to act as a unique feature during visual search. If synesthetic experiences are elicited (...) by inducers without selective attention, then a target that is distinct from the distractors by virtue of its unique synesthetic color should capture attention. This should lead to efficiency in the search that is analogous to the efficiency in searches involving unique display colors. If, however, an inducer does not elicit a synesthetic color until the subject selectively attends to it, then the search should be as inefficient as for control subjects. We found that, not only does synesthesia not provide an advantage in complicated visual search tasks, it offers a slight disadvantage, supporting the re-entrant processing hypothesis about the mechanism underlying synesthesia. (shrink)