Observers can retrieve the facing direction of a walker from point-light displays that are devoid of structure-from-motion information and retain solely local motion signals. This ability is orientation-dependent and relies on the motions representing the feet of the agent. The experiments described here were designed to investigate visual sensitivity to local cues contained in biological motion. Initial experiments revealed that local biological motion carries information about animacy in addition to the agent’s facing direction in an orientation-dependent manner (Chapter 2). The mechanism underlying the perception of local biological motion can be dissociated from that underlying the retrieval of global structure-from-motion information according to characteristics such as sensitivity to learning and noise (Chapter 3). Further experiments revealed that the orientation-dependency for perceiving local biological motion is carried by vertical acceleration in the foot’s motion (Chapter 4). The importance of acceleration for biological motion perception raises the need to achieve a better understanding of acceleration sensitivity across various parameters such as stimulus size. To this end, Chapter 5 showed that acceleration thresholds for perceiving a linearly accelerating stimulus scale according to mean velocity as predicted by size invariance and are inversely proportional to stimulus duration. An important role for acceleration for the perception of biological motion was further corroborated by findings in an evolutionarily guided psychophysical search for the adequate local motion, defined as one that carries maximal directional information and a large inversion effect (Chapter 6). Finally, although orientation-dependency is a pervasively demonstrated characteristic of biological motion perception, the reference systems in which the stimuli are encoded are unclear. The experiments in Chapter 7 revealed that both global structure and local motion aspects of biological motion, like faces, are primarily coded in an egocentric frame of reference. Unlike faces however, there is an additional contribution of non-visual information about gravity for the perception of biological motion. These findings are finally discussed in the context of emerging behavioural, neuroimaging, and electrophysiological work that further characterize a local motion mechanism that is proposed to serve as a fundamental first stage towards interpreting animate motion patterns. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2010-07-21 08:34:58.564

Understanding how the human visual system recognizes objects is one of the key challenges in neuroscience. Inspired by a large body of physiological evidence (Felleman and Van Essen, 1991; Hubel and Wiesel, 1962; Livingstone and Hubel, 1988; Tso et al., 2001; Zeki, 1993), a general class of recognition models has emerged which is based on a hierarchical organization of visual processing, with succeeding stages being sensitive to image features of increasing complexity (Hummel and Biederman, 1992; Riesenhuber and Poggio, 1999; Selfridge, 1959). However, these models appear to be incompatible with some well-known psychophysical results. Prominent among these are experiments investigating recognition impairments caused by vertical inversion of images, especially those of faces. It has been reported that faces that differ "featurally" are much easier to distinguish when inverted than those that differ "configurally" (Freire et al., 2000; Le Grand et al., 2001; Mondloch et al., 2002) ??finding that is difficult to reconcile with the aforementioned models. Here we show that after controlling for subjects' expectations, there is no difference between "featurally" and "configurally" transformed faces in terms of inversion effect. This result reinforces the plausibility of simple hierarchical models of object representation and recognition in cortex.

Anthropomorphism is a common phenomenon when people attribute human characteristics to non-human objects. It plays an important role in acceptance of robots in natural human environments. Various studies in the field of Human-Robot Interaction (HRI) show that there are various factors that can affect the extent to which a robot is anthropomorphized. However, our knowledge of this phenomenon is segmented, as there is a lack of a coherent model of anthropomorphism that could consistently explain these findings. A robot should be able to adjust its level of anthropomorphism to a level that can optimize its task performance. In order to do that, robotic system designers must know which characteristics affect the perception of robots' anthropomorphism. Currently, existing models of anthropomorphism emphasize the importance of the context and perceiver in this phenomenon, but provide little guidelines regarding the factors of a perceived object that are affecting it. The proposed reverse process to anthropomorphization is known as dehumanization. In the recent years research in social psychology has found which characteristics are deprived from people who are perceived as subhumans or are objectified. Furthermore, the process of dehumanization is two dimensional rather than unidimensional. This thesis discusses a model of anthropomorphism that uses characteristics from both dimensions of dehumanization and those relating to robots' physical appearance to affect the anthropomorphism of a robot. Furthermore, involvement of implicit and explicit processes in anthropomorphization are discussed. In this thesis I present five empirical studies that were conducted to explore anthropomorphism in HRI. Chapter 3 discusses development and validation of a cognitive measurement of humanlikeness using the magnitude of the inversion effect. Although robot stimuli were processed more similarly to human stimuli rather than objects and induced the inversion effect, the results suggest that this measure has limited potential for measuring humanlikeness due to the low variance that it can explain. The second experiment, presented in Chapter 4 explored the involvement of Type I and Type II processing in anthropomorphism. The main findings of this study suggest that anthropomorphism is not a result of a dual-process and self-reports have a potential to be suitable measurement tools of anthropomorphism. Chapter 5 presents the first empirical work on the dimensionality of anthropomorphism. Only perceived emotionality of a robot, but not its perceived intelligence, affects its anthropomorphization. This finding is further supported by a follow up experiment, presented in Chapter 6, that shows that Human Uniqueness dimension is less relevant for a robot's anthropomorphiazability than Human Nature (HN) dimension. Intentionality of a robot did not result in its higher anthropomorphizability. Furthermore, this experiment showed that humanlike appearance of a robot is not linearly related with its anthropomorphism during HRI. The lack of linear relationship between humanlike appearance and attribution of HN traits to a robot during HRI is further supported by the study described in Chapter 7. This last experiment shows also that another factor of HN, sociability, affects the extent to which a robot is anthropomorphized and therefore the relevance of HN dimension in the process of anthropomorphization. This thesis elaborates on the process of anthropomorphism as an important factor affecting HRI. Without fully understanding the process itself and what factors make robots to be anthropomorphized it is hard to measure the impact of anthropomorphism on HRI. It is hoped that understanding anthropomorphism in HRI will make it possible to design interactions in a way that optimizes the benefits of that phenomenon for an interaction.

Understanding how the human visual system recognizes objects is one of the key challenges in neuroscience. Inspired by a large body of physiological evidence (Felleman and Van Essen, 1991; Hubel and Wiesel, 1962; Livingstone and Hubel, 1988; Tso et al., 2001; Zeki, 1993), a general class of recognition models has emerged which is based on a hierarchical organization of visual processing, with succeeding stages being sensitive to image features of increasing complexity (Hummel and Biederman, 1992; Riesenhuber and Poggio, 1999; Selfridge, 1959). However, these models appear to be incompatible with some well-known psychophysical results. Prominent among these are experiments investigating recognition impairments caused by vertical inversion of images, especially those of faces. It has been reported that faces that differ “featurally” are much easier to distinguish when inverted than those that differ “configurally” (Freire et al., 2000; Le Grand et al., 2001; Mondloch et al., 2002) – a finding that is difficult to reconcile with the aforementioned models. Here we show that after controlling for subjects’ expectations, there is no difference between “featurally” and “configurally” transformed faces in terms of inversion effect. This result reinforces the plausibility of simple hierarchical models of object representation and recognition in cortex.

This thesis explores the causes of the face inversion effect, which is a substantial decrement in performance in recognising facial stimuli when they are presented upside down (Yin,1969). I will provide results from both behavioural and electrophysiological (EEG) experiments to aid in the analysis of this effect. Over the course of six chapters I summarise my work during the four years of my PhD, and propose an explanation of the face inversion effect that is based on the general mechanisms for learning that we also share with other animals. In Chapter 1 I describe and discuss some of the main theories of face inversion. Chapter 2 used behavioural and EEG techniques to test one of the most popular explanations of the face inversion effect proposed by Diamond and Carey (1986). They proposed that it is the disruption of the expertise needed to exploit configural information that leads to the inversion effect. The experiments reported in Chapter 2 were published as in the Proceedings of the 34th annual conference of the Cognitive Science Society. In Chapter 3 I explore other potential causes of the inversion effect confirming that not only configural information is involved, but also single feature orientation information plays an important part in the inversion effect. All the experiments included in Chapter 3 are part of a paper accepted for publication in the Quarterly Journal of Experimental Psychology. Chapter 4 of this thesis went on to attempt to answer the question of whether configural information is really necessary to obtain an inversion effect. All the experiments presented in Chapter 4 are part of a manuscript in preparation for submission to the Quarterly Journal of Experimental Psychology. Chapter 5 includes some of the most innovative experiments from my PhD work. In particular it offers some behavioural and electrophysiological evidence that shows that it is possible to apply an associative approach to face inversion. Chapter 5 is a key component of this thesis because on the one hand it explains the face inversion effect using general mechanisms of perceptual learning (MKM model). On the other hand it also shows that there seems to be something extra needed to explain face recognition entirely. All the experiments included in Chapter 5 were reported in a paper submitted to the Journal of Experimental Psychology; Animal Behaviour Processes. Finally in Chapter 6 I summarise the implications that this work will have for explanations of the face inversion effect and some of the general processes involved in face perception.

The face inversion effect (FIE; Yin, 1969) raises the question of whether upright face identification is mediated by a special mechanism that is disrupted by inversion. The present study investigates the effect of face inversion on the perceptual encoding of spatial frequency (SF) information using a novel variant of the Bubbles technique (Gosselin & Schyns, 2001). In Experiment 1, the SF Bubbles technique was validated using a simple plaid detection task. In Experiment 2, SF tuning of upright and inverted face identification was measured. While the data showed a clear FIE (28% higher accuracy and 455 ms shorter reaction times for upright faces), SF tunings were remarkably similar in both conditions (r = .96; a single SF band of ~2 octaves peaking at ~9 cycles per face width). Experiments 3 and 4 demonstrated that SF Bubbles is sensitive to bottom-up and top-down induced changes in SF tuning, respectively. Overall, the results show that the same SFs are utilized in upright and inverted face identification, albeit not with equal efficiency.

The face inversion effect (FIE; Yin, 1969) raises the question of whether upright face identification is mediated by a special mechanism that is disrupted by inversion. The present study investigates the effect of face inversion on the perceptual encoding of spatial frequency (SF) information using a novel variant of the Bubbles technique (Gosselin & Schyns, 2001). In Experiment 1, the SF Bubbles technique was validated using a simple plaid detection task. In Experiment 2, SF tuning of upright and inverted face identification was measured. While the data showed a clear FIE (28% higher accuracy and 455 ms shorter reaction times for upright faces), SF tunings were remarkably similar in both conditions (r = .96; a single SF band of ~2 octaves peaking at ~9 cycles per face width). Experiments 3 and 4 demonstrated that SF Bubbles is sensitive to bottom-up and top-down induced changes in SF tuning, respectively. Overall, the results show that the same SFs are utilized in upright and inverted face identification, albeit not with equal efficiency.

付記する学位プログラム名: 霊長類学・ワイルドライフサイエンス・リーディング大学院 / 京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22721号 / 理博第4630号 / 新制||理||1665(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 足立 幾磨, 准教授 後藤 幸織, 教授 高田 昌彦 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The human visual system must quickly and accurately deploy task-and-object-specific processing to successfully navigate the environment, which suggests several interesting research questions: What is the nature of these strategies? Are they flexible? To what extent is this behaviour optimal given the natural statistics of the environment? In this thesis, I explored these questions using human faces, a complex and dynamic source of socially relevant information that we encounter throughout our lives. Specifically, I conducted several experiments examining the role of horizontally-oriented spatial frequency components in face identification. In Chapter 2, I use computational modelling to demonstrate that the structure conveyed by these components is maximally diagnostic for face identity, and show that selective processing of this structure predicts both face identification performance and the face inversion effect. In Chapter 3, I quantify the bandwidth utilized by human observers and relate this sampling strategy to the information structure of face stimuli. In Chapter 4, I show that the selective sampling described in Chapters 2 and 3 is driven by information from the eyes. Finally, in Chapter 5, I show that the impaired horizontal selectivity associated with face inversion is enhanced by practice identifying inverted faces. Together, these experiments characterize a stimulus with differentially diagnostic information sources that, through experience, becomes selectively processed in a manner associated with task performance. These results contribute to our understanding of expert object processing and may have implications for observers experiencing face perception deficits. / Thesis / Doctor of Philosophy (PhD)

<p>Holistic processing has been deemed a crucial part of human face processing. There are three tasks that are indexes of holistic processing and each is used by many researchers for the purposes of demonstrating that either their participants have intact holistic processing or that holistic processing is impaired or missing. The tasks that demonstrate holistic processing are the face inversion, composite face, and the whole-part tasks. In this dissertation, I evaluate the hypothesis that holistic processing is important for face identification. A secondary hypothesis that is evaluated is whether the three indexes of holistic processing are related and whether they are tapping the same underlying process. Chapter 2 tests the first hypothesis in a large group of young adults and shows that the composite face effect (an index of holistic processing) is not related to accuracy on two identification tasks. Chapter 3 tested both hypotheses and showed that none of the holistic indexes are related to one another and they are unrelated to face identification accuracy. In Chapter 4, a large group of older adults are tested on the composite face task and a face identification task, similar to Experiment 2 from Chapter 2. Unlike the results for young adults, older adults show a significant positive correlation between the composite face effect and identification accuracy even though older adults perform worse on the identification task.</p> / Doctor of Philosophy (PhD)