Robot faces elicit responses intermediate to human faces and objects at face-sensitive ERP components

Face recognition is supported by selective neural mechanisms that are sensitive to various aspects of facial appearance. These include event-related potential (ERP) components like the P100 and the N170 which exhibit different patterns of selectivity for various aspects of facial appearance. Examining the boundary between faces and non-faces using these responses is one way to develop a more robust understanding of the representation of faces in extrastriate cortex and determine what critical properties an image must possess to be considered face-like. Robot faces are a particularly interesting stimulus class to examine because they can differ markedly from human faces in terms of shape, surface properties, and the configuration of facial features, but are also interpreted as social agents in a range of settings. In the current study, we thus chose to investigate how ERP responses to robot faces may differ from the response to human faces and non-face objects. In two experiments, we examined how the P100 and N170 responded to human faces, robot faces, and non-face objects (clocks). In Experiment 1, we found that robot faces elicit intermediate responses from face-sensitive components relative to non-face objects (clocks) and both real human faces and artificial human faces (computer-generated faces and dolls). These results suggest that while human-like inanimate faces (CG faces and dolls) are processed much like real faces, robot faces are dissimilar enough to human faces to be processed differently. In Experiment 2 we found that the face inversion effect was only partly evident in robot faces. We conclude that robot faces are an intermediate stimulus class that offers insight into the perceptual and cognitive factors that affect how social agents are identified and categorized.

Scintillating Starbursts: Concentric Star Polygons Induce Illusory Ray Patterns

Here, we introduce and explore Scintillating Starbursts, a stimulus type made up of concentric star polygons that induce illusory scintillating rays or beams. We test experimentally which factors, such as contrast and number of vertices, modulate how observers experience this stimulus class. We explain how the illusion arises from the interplay of known visual processes, specifically central versus peripheral vision, and interpret the phenomenology evoked by these patterns. We discuss how Starbursts differ from similar and related visual illusions such as illusory contours, grid illusions such as the pincushion grid illusion as well as moiré patterns.

Not quite human, not quite machine: Electrophysiological responses to robot faces

Face recognition is supported by selective neural mechanisms that are sensitive to various aspects of facial appearance. These include ERP components like the P100, N170, and P200 which exhibit different patterns of selectivity for various aspects of facial appearance. Examining the boundary between faces and non-faces using these responses is one way to develop a more robust understanding of the representation of faces in visual cortex and determine what critical properties an image must possess to be considered face-like. Here, we probe this boundary by examining how face-sensitive ERP components respond to robot faces. Robot faces are an interesting stimulus class because they can differ markedly from human faces in terms of shape, surface properties, and the configuration of facial features, but are also interpreted as social agents in a range of settings. In two experiments, we examined how the P100 and N170 responded to human faces, robot faces, and non-face objects (clocks). We found that robot faces elicit intermediate responses from face-sensitive components relative to non-face objects and both real and artificial human faces (Exp. 1), and also that the face inversion effect was only partly evident in robot faces (Exp. 2). We conclude that robot faces are an intermediate stimulus class that offers insight into the perceptual and cognitive factors that affect how social agents are identified and categorized.

The N170 as a marker of Reading Proficiency

The major aim of the thesis is to investigate a new biological marker for reading proficiency. One typical marker for dyslexia is the mismatch negativity (MMN) of the auditory event-related brain potential. In the present studies I shall explore a marker that is more reading-specific: the N170 component (also called N1). This component is more reading specific because it responds to and is modulated by visual stimuli depending on the expertise of the reader with a specific stimulus class such as words or faces. In contrast, the MMN is primarily sensitive to deviant auditory stimuli in an otherwise consistent series of auditory events. The first two studies examined whether there is a correlation between habituation of the N170 and reading speed in adult normal readers and 2nd graders. The ongoing habituation of the N170 signal represents the automatization of the reading process. In a third study rhymes were used to explore the relation between N170 laterality, phonological abilities (rhyming) and reading ability/speed.

Meta-Control in Pigeons (Columba livia) and the Role of the Commissura Anterior

Meta-control describes an interhemispheric response conflict that results from the perception of stimuli that elicit a different reaction in each hemisphere. The dominant hemisphere for the perceived stimulus class often wins this competition. There is evidence from pigeons that meta-control results from interhemispheric response conflicts that prolong reaction time when the animal is confronted with conflicting information. However, recent evidence in pigeons also makes it likely that the dominant hemisphere can slow down the subdominant hemisphere, such that meta-control could instead result from the interhemispheric speed differences. Since both explanations make different predictions for the effect of commissurotomy, we tested pigeons in a meta-control task both before and after transection of the commissura anterior. This fiber pathway is the largest pallial commissura of the avian brain. The results revealed a transient phase in which meta-control possibly resulted from interhemispheric response conflicts. In subsequent sessions and after commissurotomy, however, the results suggest interhemispheric speed differences as a basis for meta-control. Furthermore, they reveal that meta-control is modified by interhemispheric transmission via the commissura anterior, although it does not seem to depend on it.

Can Dogs Learn Concepts the Same Way We Do? Concept Formation in a German Shepherd

Growing evidence shows that dogs can complete complex behavioral tasks, such as learning labels for hundreds of objects, readily learning the name of a novel object, and responding differentially to objects by category (e.g., “toy,” “ball,” “Frisbee”). We expand here on the evidence for complex behavioral abilities in dogs by demonstrating that they are capable of concept formation by strict criteria. A German shepherd responded differentially to two sets of objects (“toys” and “non-toys”) in Experiment 1. Additionally, the dog’s differential responding in Experiment 1 occurred from the first trial, indicating that he entered the experiment with this stimulus class already differentiated from his day-to-day exposure to contingencies. In Experiment 2 we used a common response (tug-of-war) with three objects that were not retrieved in Experiment 1 to attempt to add these objects to the stimulus class. After repeated sessions of tug-of-war, the dog began retrieving all three objects in the retrieval test, although the rates of retrieval varied between objects. Finally, in Experiment 3, we conducted a transfer of function test in which the dog emitted a new response to untrained exemplars suggesting that his differential responding in Experiment 1 was indicative of a concept by the strictest criteria. Additionally, he reliably emitted the new response in the transfer test to one of the three new objects from Experiment 2, suggesting this object had been reliably added to the conceptual class.

The physiology of perception in human temporal lobe is specialized for contextual novelty

The human ventral temporal cortex has regions that are known to selectively process certain categories of visual inputs; they are specialized for the content (“faces,” “places,” “tools”) and not the form (“line,” “patch”) of the image being seen. In our study, human patients with implanted electrocorticography (ECoG) electrode arrays were shown sequences of simple face and house pictures. We quantified neuronal population activity, finding robust face-selective sites on the fusiform gyrus and house-selective sites on the lingual/parahippocampal gyri. The magnitude and timing of single trials were compared between novel (“house-face”) and repeated (“face-face”) stimulus-type responses. More than half of the category-selective sites showed significantly greater total activity for novel stimulus class. Approximately half of the face-selective sites (and none of the house-selective sites) showed significantly faster latency to peak (∼50 ms) for novel stimulus class. This establishes subregions within category-selective areas that are differentially tuned to novelty in sequential context, where novel stimuli are processed faster in some regions, and with increased activity in others.