CLPS0020: Introduction to Cognitive Science Face recognition CLPS0020: Introduction to Cognitive Science Professor Dave Sobel Fall 2016 Today’s topic: General introduction Expertise on face recognition Holistic processing FFA Not all faces are equal for recognition: Other race effects

Let’s start with this question How many faces do we perceive in a lifetime? We interact with 80,000 people Millions? How similar are faces? Faces share similar 3D structure. Still, we are good at recognizing faces. We also “see” faces in non-faces. (e.g. Cydonia and more) Exception: prosopagnosic patients.

Features of Faces: Homogeneous Faces versus Telephones for biological constraints. Homogeneous in contrast to other object categories. Also face is one of the largest class. Also faces can be classified in many different ways: sex, expressions, trustfulness, attractiveness, symmetry, etc.

Even infants are sensitive to that homogeneity in recognition Remain Habituated (Yes, a dog) Dishabituate (Not a cat)

Holistic processing Means we are processing the whole, and not just the parts. “Holistic” is opposite of feature(part)-based representation. Faces are perceived in terms of configuration. The structural relation between individual features on the face matters. Either because they are special or they require a certain level of expertise. Beyond individual features! Forest rather than tree. We cannot perceive facial features in isolation from the other facial features. When a face is upside down, the configural processing cannot take place, and so differences are more difficult to detect.

Evidence of holistic processing Whole/part advantage (Tanaka & Sengco, 1997) Facial features were recognized better when presented in their original configuration than in a new configuration or in isolation Example of study face with close-together eye spacing. In this example, memory for nose feature is tested when shown in isolation, in a new configuration (i.e., far-apart eye spacing), and in the old configuration (i.e., close-together eye spacing). This whole-face advantage did not appear with house.

Evidence of holistic processing Inversion effect When faces are viewed upside-down, our ability to process is disrupted. e.g. Thatcher effect (Thompson, 1980) Inversion effect: Just ONE page!!! Sensational! Old/new task. Upside-down faces showed poorer performance. When a face is upside down, the configural processing cannot take place, and so minor differences are more difficult to detect. This effect is not present in people who have some forms of prosopagnosia Normal subjects performed better (94% correct) for upright than for inverted (82% correct) faces. This implies specialized processing for faces. Patient LH suffers from prosopagnosia. LH did relatively poorly compared to control subjects on both upright and inverted faces. But interestingly, he performed better (72% correct) for inverted than for upright (58% correct). A disproportionate impairment on upright relative to inverted faces implies an impairment of a face-specific processor, which is engaged by the upright but not the inverted faces, and used despite being disadvantageous. About psy: I really hope I can play the song…

Interpretation? Special Evolutionary Mechanism, or are we Face Expertise? How do you show that a cognitive mechanism has an evolutionary origin? Use logic from nativism Intact processing at birth Shared with other species Unique neural substrate Face recognition is a highly specialized skill that emerges during infancy, continues to develop throughout childhood, and becomes adult-like in late adolescence. Quite long learning phase. Gradually developed. Newborns: They prefer a face-like pattern over a checkerboard-like pattern. Newborns can recognize the face of their mother from visual cues alone: infants as 'young as 3 days old fixate their mother's face longer than the face of a stranger. FYI: How grounded face recognition is? Early visual deprivation has no apparent effect on the later development of recognition of facial identity based on individual features (featural ing). Deprived patients can easily distinguish faces that differ only in the shape of individual features (Le Grand, Mondloch, Maurer, & Brent, 2001), even when there are no striking changes in the color or size of the eyes (Mondloch et aI., 2008), and they can match faces based on emotional expression, vowel being mouthed, and direction of eye gaze (Geldart, Mondloch, Maurer, de Schonen, & Brent, 2002)-tasks that can be per­ formed by processing local features.

Processing of Faces at birth At birth, infant registers others’ facial expressions Imitation At birth, infant also track face configurations over similar features (Johnson et al., 1991) Shared by chicks (Morton & Johnson, 1991)

Fusiform face area (FFA) Kanwisher et al. Fusiform Gryus is the anatomical location of face perception This area is selectively activated by faces. Answer to Q2: Does this expertise require brain region only dedicated to face processing? Kanwisher et al. (1997): FFA responded significantly more strongly during passive viewing of face than object stimuli.

FFA as face-selective brain region Kanwisher et al. (1997) This region does not simply respond to any animal or human images or body parts but only to faces! It generalizes to respond to images of faces taken from a different viewpoint that differed considerably in their low-level visual features from the original set of face images. Area FF responds to a wide variety of face stimuli, including front-view gray-scale photographs of faces, two-tone versions of the same faces, and three-quarter-view gray-scale faces with hair concealed. Conclusion: It demonstrates the existence of a region in the fusiform gyrus that is not only responsive to face stimuli but is selectively activated by faces compared with various control stimuli. We show how strong evidence for cortical specialization can be obtained by testing the responsiveness of the same region of cortex on many different stimulus comparisons. The fact that special-purpose cortical machinery exists for face perception suggests that a single general and overarching theory of visual recognition may be less successful than a theory that proposes qualitatively different kinds of computations for the recognition of faces compared with other kinds of objects.

Evidence against these ideas Facial imitation and face tracking both have short developmental trajectories Consider Face Tracking Newborns track, by 1-3 months, infants don’t track, but tracking then returns at 5 months (Morton & Johnson, 1991). Considered evidence for two systems. The first is a perceptual system that recognizes configuration of facial features (CONSPEC). The second is one that actually recognizes faces for social categorization (CONLEARN) Distinction between perception and recognition

Different interpretation of FFA Gauthier, Tarr et al. Is FFA truly dedicated to face-processing? FFA as an area for recognizing objects that requires expertise. Greebles experiment. Greebles are artificial objects with the same number of parts in the same configuration as faces. They are NOT faces. The Greebles form a category of computer-generated novel objects that were originally designed as a control set for faces, so that people could be trained to become "Greeble experts". At first, performance was like that for objects, e.g., no inversion effect. In a part-based fashion comparable to the way they recognize other non-face objects. After lots of practice, performance was like that for faces, i.e., better at recognizing upright greebles. In a holistic and configural fashion, similar to the way we tend to treat upright faces

Expertise, rather than faces Gauthier et al. (1997) The left two columns are from before practice: when subjects viewed pictures of greebles there was no activity in the "face" area (small white outline).  The right two colums were made after lots of practice: the brain activity shifted to the "face" area so that the brain activity was very similar for Greebles and for faces. Debates still going on..

More Expertise and Conclusions Bird Experts see FFA activation for birds not cars. Car experts see FFA activation for cars, not birds (Gauthier et al., 2000). Conclusions Faces are processed holistically unlike other objects We are born interested in faces (perceptual process or recognition process?) Fusiform face area (FFA) is a brain area in adults dedicated to faces (and/or objects requiring expertise) Still under debate