Aphantasia, i.e., the inability to voluntarily form visual mental images, affects approximately 2 to 5 percent of the population and plays an important role in a more general debate revolving around the role of imagery for our cognition. This thesis investigates aphantasia by means of an interdisciplinary approach, combining insights from contemporary neuroscientific research with historical philosophical arguments, with a specific focus on the later philosophy of Ludwig Wittgenstein. A new theoretical concept, meta-imagination, is developed and it is argued that (...) the concept can explain why aphantasics perform successfully on a wide range of visual imagery tasks, thus providing important implications for the more general debate about the connection between imagery and cognition. (shrink)

In a variety of synaesthesia, photisms result from affect-laden stimuli as emotional words, or faces of familiar people. For R, who participated in this study, the sight of a familiar person triggers a mental image of "a human silhouette filled with colour". Subjective descriptions of synaesthetic experiences induced by the visual perception of people's figures and faces show similarities with the reports of those who claim to possess the ability to see the aura. It has been proposed that the purported (...) auric perception may be easily explained by the presence of a specific subtype of cross-modal perception. We analyse the subjective reports of four synaesthetes who experience colours in response to human faces and figures. These reports are compared with descriptions of alleged auric phenomena found in the literature and with claims made by experts in esoteric spheres. The discrepancies found suggest that both phenomena are phenomenologically and behaviourally dissimilar. (shrink)

Mental imagery (varieties of which are sometimes colloquially refered to as “visualizing,” “seeing in the mind's eye,” “hearing in the head,” “imagining the feel of,” etc.) is quasi-perceptual experience; it resembles perceptual experience, but occurs in the absence of the appropriate external stimuli. It is also generally understood to bear intentionality (i.e., mental images are always images of something or other), and thereby to function as a form of mental representation. Traditionally, visual mental imagery, the most discussed variety, was thought (...) to be caused by the presence of picturelike representations (mental images) in the mind, soul, or brain, but this is no longer universally accepted. (shrink)

Synaesthesia is a heterogeneous phenomenon, even when considering one particular sub-type. The purpose of this study was to design a reliable and valid questionnaire for grapheme-colour synaesthesia that captures this heterogeneity. By the means of a large sample of 628 synaesthetes and a factor analysis, we created the Coloured Letters and Numbers questionnaire with 16 items loading on 4 different factors . These factors were externally validated with tests which are widely used in the field of synaesthesia research. The questionnaire (...) showed good test–retest reliability and construct validity . Our findings are discussed in the light of current theories and new ideas in synaesthesia research. More generally, the questionnaire is a useful tool which can be widely used in synaesthesia research to reveal the influence of individual differences on various performance measures and will be useful in generating new hypotheses. (shrink)

Determining the nature of binding in grapheme-color synaesthesia has consequences for understanding the neural basis of synaesthesia and visual awareness in general. We evaluated type- and token-based letter-color binding using a synaesthetic version of the object-reviewing paradigm. Although mean response times failed to reveal any significant differences between synaesthetes and control participants, RT analyses with ex-Gaussian distributions revealed that the response facilitation in the synaesthesia group reflected type representations exclusively, while response facilitation in the control group, who learned letter-color associations, (...) was dominated by token representations. Thus, letter-color associations in associator synaesthetes are type-based, and do not involve binding to object tokens, consistent with their subjective reports. Contrary to recent studies that failed to find differences between synaesthetes and non-synaesthetes with behavioral measures, response time distribution analyses indicate that color sensations in synaesthetes are not simply the extreme form of normal letter-color associations, and cannot be attributed to demand characteristics. (shrink)

Synesthetic experiences of color have been traditionally conceptualized as a perceptual phenomenon. However, recent evidence suggests a role of higher order cognition in the formation of synesthetic experiences. Here, we discuss how synesthetic experiences of color differ from and influence veridical color processing, and how non-perceptual processes such as imagery and color memory might play a role in eliciting synesthetic color experience.