Abstract
The spatial distances among the features of a face are commonly referred to as second-order relations, and the coding of these properties is often regarded as a cornerstone in face recognition. Previous studies have provided mixed results regarding whether the N170, a face-sensitive component of the event-related potential, is sensitive to second-order relations. Here we investigated this issue in a gender discrimination paradigm following long-term (5 s) adaptation to normal or vertically stretched male and female faces, considering that the latter manipulation substantially alters the position of the inner facial features. Gender-ambiguous faces were more likely judged to be female following adaptation to a male face and vice versa. This aftereffect was smaller but statistically significant after being adapted to vertically stretched when compared to unstretched adapters. Event-related potential recordings revealed that adaptation effects measured on the amplitude of the N170 show strong modulations by the second-order relations of the adapter: reduced N170 amplitude was observed, however, this reduction was smaller in magnitude after being adapted to stretched when compared to unstretched faces. These findings suggest early face-processing, as reflected in the N170 component, proceeds by extracting the spatial relations of inner facial features.
Highlights
Human faces invariably contain the same basic features positioned in the same fashion
Event-related potential recordings revealed that adaptation effects measured on the amplitude of the N170 show strong modulations by the second-order relations of the adapter: reduced N170 amplitude was observed, this reduction was smaller in magnitude after being adapted to stretched when compared to unstretched faces
The Fourier phase randomized version (Nasanen, 1999) of a normal face was created and served as an adapter in the control (CTRL) condition. This image lacked any shape information while it preserved the amplitude spectrum of the original image. The inclusion of this stimulus condition was necessary for the event-related potential (ERP) analysis in order to assess the putative, category-level N170 adaptation effect; that is, the amplitude reduction in response to face repetition when compared to a condition in which the face is preceded by a non-face stimulus (Kovacs et al, 2006, 2007; Kloth et al, 2010)
Summary
Human faces invariably contain the same basic features positioned in the same fashion. This basic feature configuration is called first-order relational information (CONF1st; Diamond and Carey, 1986) and distinguishes the category of faces from other non-face object categories (Maurer et al, 2002). The variations of metric distances between these facial features is referred to as second-order relational information (CONF2nd; Diamond and Carey, 1986). Results show that humans are highly sensitive to such CONF2nd (Haig, 1984) and it has been suggested that they are important for face recognition and the discrimination of individual faces from each other (Tanaka and Farah, 1991; Tanaka and Sengco, 1997; Leder and Bruce, 2000; Rotshtein et al, 2007; Richler et al, 2009). Geometrical distortions that affect second-order relations have little or no effect on face recognition performance either (Hole et al, 2002), suggesting that the extraction of simple distances between facial features is not crucial for face recognition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
