Biomedical subjects

Alan C N Wong

Publications and source records attributed to Alan C N Wong.

4 recordsLinked to original sources

PubMed2006

Font tuning associated with expertise in letter perception.

Font tuning (FT) occurs when observers recognize a sequence of letters presented in the same font faster than in different fonts (Sanocki 1987, 1988 Journal of Experimental Psychology. Human Perception and Performance 13 267-278; 14 472-480). Here, we test the hypothesis that FT is associated with expertise with a specific writing system. We developed a systematic search task allowing the measurement of FT over a large number of letters and generalized the finding of FT from English readers viewing Roman letters to Chinese readers viewing Chinese characters. Non-Chinese readers did not show evidence of FT for Chinese characters in this search task. We also used a simpler 3-letter identification task to directly compare novice and expert readers, and to explore FT for different aspects of font such as fill, slant, and aspect ratio. We found that experts tune to aspect ratio but not to the other font changes. These findings reveal that letters are not processed visually in the same manner as shapes, and suggest an explanation for the cortical specialization obtained in the visual system for letters.

Humans↗

PubMed2005

When are viewpoint costs greater for silhouettes than for shaded images?

Previous studies of object recognition have shown efficient recognition of silhouettes, suggesting that much of the information used to recognize objects resides in the outline. These studies, however, have used objects that contain many components, which provide redundant information. In this study, we examined recognition of silhouettes of less-complex objects, so that redundant information was reduced. We found that viewpoint generalization costs (the decrement of performance when recognizing nonstudied views) were greater for silhouettes than for shaded images, even when the same qualitative components were visible in the outline of both studied and nonstudied views. Thus, silhouettes do not always allow for view generalization as efficiently as do shaded images.

Form Perception↗

PubMed2005

An early electrophysiological response associated with expertise in letter perception.

Expertise with print is likely to optimize visual processes for recognizing characters of a familiar writing system. Although brain activations have been identified for words and letter strings in contrast with other stimuli, relatively little work has focused on the neural basis of single-letter perception. English readers and Chinese-English bilinguals participated in an ERP study and performed a 1-back identity judgment on Roman letters, Chinese characters, pseudofonts, and their string versions. The Chinese-English bilinguals showed an enhanced N170 for both Roman letters and Chinese characters relative to pseudofonts. For the non-Chinese readers, the N170 amplitude was larger for Roman letters relative to Chinese characters and pseudofonts. Our results suggest that changes in relatively early visual processes underlie expert letter perception.

Adult↗

PubMed2005

Letter processing in the visual system: different activation patterns for single letters and strings.

One would expect that a lifetime of experience recognizing letters would have an important influence on the visual system. Surprisingly, there is limited evidence of a specific neural response to letters over visual control stimuli. We measured brain activation during a sequential matching task using isolated characters (Roman letters, digits, and Chinese characters) and strings of characters. We localized the visual word form area (VWFA) by contrasting the response to pseudowords against that for letter strings, but this region did not show any other sign of visual specialization for letters. In addition, a left fusiform area posterior to the VWFA was selective for letter strings, whereas a more anterior left fusiform region showed selectivity for single letters. The results of different analyses using both large regions of interest and inspections of individual patterns of response reveal a dissociation between selectivity for letter strings and selectivity for single letters. The results suggest that reading experience fine-tunes visual representations at different levels of processing. An important conclusion is that the processing of nonpronounceable letter strings cannot be assumed to be equivalent to single-letter perception.

Adult↗