The nature of upright and inverted face representations: an adaptation-transfer study of configuration

The inversion effect in word recognition: the effect of language familiarity and handwriting

Humans have expertise with visual words and faces. One marker of this expertise is the inversion effect. This is attributed to experience with those objects being biased towards a canonical orientation, rather than some inherent property of object structure or perceptual anisotropy. To confirm the role of experience, we measured inversion effects in word matching for familiar and unfamiliar languages. Second, we examined whether there may be more demands on reading expertise with handwritten stimuli rather than computer font, given the greater variability and irregularities in the former, with the prediction of larger inversion effects for handwriting. We recruited two cohorts of subjects, one fluent in Farsi and the other in Punjabi, neither of whom were able to read the other's language. Subjects performed a match-to-sample task with words in either computer fonts or handwritings. Subjects were more accurate and faster with their familiar language, even when it was inverted. Inversion effects were present for the familiar but not the unfamiliar language. The inversion effect in accuracy for handwriting was larger than that for computer fonts in the familiar language. We conclude that the word inversion effect is generated solely by orientation-biased experience, and that demands on this expertise are greater with handwriting than computer font.

Whole-object effects in visual word processing: Parallels with and differences from face recognition

Visual words and faces differ in their structural properties, but both are objects of high expertise. Holistic processing is said to characterize expert face recognition, but the extent to which whole-word processes contribute to word recognition is unclear, particularly as word recognition is thought to proceed by a component-based process. We review the evidence for experimental effects in word recognition that parallel those used to support holistic face processing, namely inversion effects, the part-whole task, and composite effects, as well as the status of whole-word processing in pure alexia and developmental dyslexia, contrasts between familiar and unfamiliar languages, and the differences between handwriting and typeset font. The observations support some parallels in whole-object influences between face and visual word recognition, but do not necessarily imply similar expert mechanisms. It remains to be determined whether and how the relative balance between part-based and whole-object processing differs for visual words and faces.

Upright or inverted, entire or exploded: right-hemispheric superiority in face recognition withstands multiple spatial manipulations

Background. The ability to identify faces has been interpreted as a cerebral specialization based on the evolutionary importance of these social stimuli, and a number of studies have shown that this function is mainly lateralized in the right hemisphere. The aim of this study was to assess the right-hemispheric specialization in face recognition in unfamiliar circumstances.

Methods. Using a divided visual field paradigm, we investigated hemispheric asymmetries in the matching of two subsequent faces, using two types of transformation hindering identity recognition, namely upside-down rotation and spatial “explosion” (female and male faces were fractured into parts so that their mutual spatial relations were left intact), as well as their combination.

Results. We confirmed the right-hemispheric superiority in face processing. Moreover, we found a decrease of the identity recognition for more extreme “levels of explosion” and for faces presented upside-down (either as sample or target stimuli) than for faces presented upright, as well as an advantage in the matching of female compared to male faces.

Discussion. We conclude that the right-hemispheric superiority for face processing is not an epiphenomenon of our expertise, because we are not often exposed to inverted and “exploded” faces, but rather a robust hemispheric lateralization. We speculate that these results could be attributable to the prevalence of right-handedness in humans and/or to early biases in social interactions.

The visual representations of words and style in text: an adaptation study

While the nature of face representations in the human perceptual system has been extensively studied using adaptation, there has been little investigation using this technique of the neural basis of another parallel class of high-level objects, words. We used the perceptual-bias technique to determine if aftereffects could be generated for either the word content or stylistic properties of textual stimuli, and if these aftereffects showed invariance for the non-adapted dimension. In a first experiment, we examined adaptation for word versus handwriting style. In a second experiment we contrasted adaptation for words with adaptation for computer font. The third experiment performed a similar study of aftereffects for words and case. In all three experiments we consistently found adaptation for words, which were not diminished by changing the style between the adapting and probe stimuli: hence word aftereffects are invariant for handwriting, font and case. Aftereffects were negligible for style. Additional analyses showed that discriminative ability was better for word than for style content. These results confirm that the neural representations of words can be probed with the adaptation technique and suggest that adaptation accesses word representations at an abstract level, where the identity of a word is invariant for stylistic properties.

Behavioral and electrophysiological correlates of intact and scrambled body perception

OBJECTIVE

Intact faces and bodies elicit two prominent electrophysiological components (P100 and N170). The N170 is thought to be related to the structural encoding and configural processing of faces and bodies. The aim of the present study was to investigate whether intact faces and bodies as well as scrambled faces and bodies elicit the same component. This would imply that similar as faces, bodies are encoded as a whole.

METHODS

We used a matching to sample task and two manipulations validated as an assessment of configural processing in previous studies: the inversion effect and intact versus scrambled stimulus presentation.

RESULTS

For both categories, performance was better for intact compared to scrambled stimuli. Additionally, stimulus distortion seems to abolish the body but not the face inversion effect. On the electrophysiological level, we found enhanced N170 amplitudes for intact faces and bodies compared to scrambled stimuli. The opposite pattern engaged in the time-window of the P100. Furthermore, for the N170 we observed an inversion effect for intact but not scrambled bodies.

CONCLUSIONS

First-order relational information are important for the perception of bodies and might be processed in the N170 time-window. Disrupting this information interacts with the inversion effect.

SIGNIFICANCE

The current data suggest that faces and bodies might be processed by distinct mechanisms as the experimental manipulation affected faces in a different way than bodies.