Early processing in the recognition of faces 49 4 Empirical Studies In the following part of this work, several experiments will be presented which investigate the early processing in face recognition. The structure is as follows: first, open questions in the field of face processing will be discussed (chapter 4.1). In chapter 4.2, a short introduction to general methodical aspects of this work is given. After these more general parts, specific ex- periments are described that investigate the open questions. This will be done in two separate parts. One investigates microgenetic face processing models with unfamiliar faces (chapter 4.3); the other examines hypotheses dealing with local face analyses of famous faces (chapter 4.4). For the experiments using unfamiliar faces, artificial facial material was constructed. In order to create standardized facial material, the distinctiveness of specific facial parts was evaluated and combined systematically (Pre-Study 1a and Pre-Study 2). A change detection paradigm with varied presentation times (PTs) was used to investigate the role of configural vs. featural processing within the first 100 ms in order to construct a microgenetic model of face process- ing (Exp. 1 and Exp. 2). In a second series of experiments (Exp. 3a, Exp. 3b, Exp. 4, and Exp. 5), the specific role of local features in the early face processing was investigated. Furthermore, the contextual and configural embedding of the local features were analyzed. To test these hypotheses, a Thatcher face paradigm combined with variation in presentation times (PTs) was used. Most importantly, in all experiments a systematic variation of features and configuration in combination with the usage of limited presentation made it possible to test specific processing hypotheses. 4.1 Open questions In the previous chapters, theoretical and empirical accounts of face recognition were intro- duced. There are many open questions left in this field of research, especially in respect to the processing of faces. The aim of this section is to briefly address some of these unresolved problems. Moreover, it will be explained how the following studies and experiments attempt to investigate these problems. How much is processed in early processing? In section 2.3, the early processing of objects and faces was discussed. It was demonstrated that within only 100 ms of presentation, simple structures were already recognizable. Bieder- man (1981) has even demonstrated that a presentation time of about 80 ms (20-80 ms accord- ing to Delorme, Richard et al., 1999) is generally sufficient to recognize general structures Early processing in the recognition of faces 50 and semantics of a more complex natural scene. In this work, this time period of the first 100 milliseconds of a presentation will be investigated further, particularly in respect to what kind of information is available. Role of distinctiveness in face processing Distinctiveness seems to be an important factor for the nature of ongoing processing (see sec- tion 3.1.1). In Experiment 1 and Experiment 2, the impact of the distinctiveness of several features on the face recognition process will be studied. Microgenesis In recent years, the microgenetic approach to pattern recognition has become quite popular (Sergent, 1986b; Watt, 1988), as described in section 3.2. The main idea behind this approach is that different levels or aspects of the image become perceptually available at different mo- ments of real time while this accumulative process of percept development is occurring (Bachmann, 1991). Thus it is assumed that our visual representation of a scene is not achieved in one step. It is attained incrementally. One of the most important issues of the present work will be to analyze the microgenesis of early face recognition. Therefore, in Experiment 1 con- crete processing models will be tested. The logic behind these models is a microgenesis of the processing of single face features or face regions. Relationship between configural and local information As described in section 3.1, there are some hints that configural/relational and featural/local aspects of a face are dissociable and are not based on the same cognitive processes. The ques- tion is whether configurally or locally changed faces also differ in terms of the nature of their processing. Experiment 1 and Experiment 2 will investigate this question with systematically constructed faces, which are manipulated in either configural or local aspects. Moreover, in supplementary experiments, the special role of local feature analysis (see section 3.1.1) and its relationship to configural information will be analyzed further. One prominent question is whether both information qualities are already binded if faces are only presented very briefly (see section 3.2.3). Global precedence Section 3.2.3 described many processing examples in which global structures preceded local structures. In Experiment 4 and Experiment 5, the involvement and quality of global process- ing will be tested. Moreover, the relationship between global processing within different pres- entation time constraints will be studied. Holistic processing The assumption of holistic face processing is intuitive and has often been validated. Neverthe- less, the important question remains whether holistic processing occurs even after only a short glance (see section 3.1.3). The experimental series using familiar faces will search for benefi- cial holistic processing in comparison to specialized local feature analyses. 4.2 Methodological Introduction The central issue of this section will be to discuss methodological aspects of the experiments described and discussed in the empirical part of this work. Its aim is to explain why and under which specific conditions particular stimuli will be used. Furthermore, it has to be discussed which general methodical problems are expected to emerge in such experiments, and how they can be solved. Early processing in the recognition of faces 51 4.2.1 Stimuli The muscles in our face enable us to make up to 7000 distinct expressions (Ekman et al., 1972). But just as is the case for our spoken vocabulary, in normal day-to-day life we only use a small proportion of this repertoire—a few hundred expressions (Bates & Cleese, 2001). Ex- pression analysis and the impact of expression on face recognition is an interesting but also vast field of research (Frijda, 1986). In the present work, solely the early processing in the recognition of faces will be investi- gated. To do so, neutral and static faces will be used that were photographed frontally. These faces will be highly standardized. Many results have shown that transformed faces with changed expression are identified less accurately than untransformed faces (Parkin & Good- win, 1983). These factors, despite their advantage of improving the ecological validity, de- crease the inner validity and the possibility to obtain recognition rates above the base rate when a task is very difficult. Static faces were employed as well (as argued in Knight & Johnston, 1996) to focus on the small areas of interest, the eyes, the nose, and the mouth, whereas movement studies are important to study the more elaborate face recognition per- formance after early processing is completed (e.g., Lander, Christie, & Bruce, 1999; Lander & Bruce, 2001). The focus can be obtained more easily when there is great homogeneity in the stimuli. Moreover, to make the pictures of the faces as realistic as possible (regardless of the con- straints discussed above), only photographic materials were used in the present studies. Bachmann (1991) pointed out that Identikit faces as well as other frequently used schematic faces might be processed in a different way than natural faces. The use of schematic faces poses some serious problems in regard to the generalizability of the conclusions drawn from these studies. First, it is well known that texture (Hill & Bruce, 1996) and color (Lee & Per- rett, 1997) play an important role in face recognition, and it is desirable to use realistic stim- uli. Under some conditions, impoverished representation leads to an unrealistic, differential weighting of facial features (Leder, 1996). In addition, all faces in the present work were Caucasian, to avoid racial stereotyping (Zebrowitz et al., 1993) and to refer to the same race expertise (Valentine, 1991; Valentine et al., 1995; Valentine & Bruce, 1986b; O'Toole, Deffenbacher, Valentin, & Abdi, 1994; Levin, 1996; Hill et al., 1995; Dehon & Brédart, 2001; Bothwell, Brigham, & Malpass, 1989). See section 2.2.1 for more details. Unfamiliar vs. familiar faces Bruce and Young (1986) support the view that different functional components are responsi- ble for the recognition of familiar faces than for the temporary storage and matching of repre- sentations of unfamiliar faces. Indeed, familiar and unfamiliar faces could be dissociated neurologically (Paller, Gonsalves, Grabowecky, Bozic, & Yamada, 2000; Young, Hay, McWeeny, Flude, & Ellis, 1985). In a very early finding, Warrington and James (1967) showed that although lesions of the right cerebral hemisphere were able to affect the recogni- tion of familiar and unfamiliar faces, such impairments of familiar or unfamiliar face recogni- tion did not correlate with each other. Familiar faces are generally found to be recognized with a right-hemisphere advantage in contrast to unfamiliar faces (cf. Carey & Diamond, 1994; Moscovitch, Scullion, & Christie, 1976). Other results validate the dissociation