Bilişsel Bilim

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A computational model and psychological investigation of event segmentation and learning
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2021., 2021.) Başgöl, Hamit.; Uğur, Emre.; Ayhan, İnci.
Event is a fuzzy term that refers to bounded spatio-temporal units, which guide behavior to allow adaptation to complex environments. The study of event segmentation investigates mechanisms behind detecting these spatial-temporal units. Event segmentation theory states that people predict ongoing activities and monitor their prediction errors for segmentation. In this study, the mechanism underlying the event segmentation ability was enlightened with computational models and psychological experiments. Firstly, inspired by event segmentation theory and predictive processing, a computational model of event segmentation and learning was introduced. The performance of the model was compared with humans in point-light displays-based psychological experiments to verify that it can segment ongoing activity into meaningful units, learn them via passive observation, and represent them in its internal representational space. Results indicated that the computational model reached a comparable performance to humans in event segmentation and event representation experiments. Secondly, focusing on the role of prediction errors in event segmentation, several psychological experiments were conducted with the aim of revealing the effect of sensory information (bottom-up processes) and expectation (top-down influence) on perceived event boundaries. Results of psychological experiments were discussed in light of possible implications and future directions.
Effects of scaling shoulder width in virtual reality on reachability and pass-through-ability affordances
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2021., 2021.) Andaç, Safa.; Ayhan, İnci.; Uğur, Emre.
Perceiving affordances, the action-possibilities of a system in an environment, is a survival key for the system (Gibson, 1966). Changing invariants for the system shapes its affordance perception (Warren & Whang, 1987). Pass-through-ability of an aperture, as a perceived affordance, is determined by the fit between the apparent aspects of the environment (e.g., perceived gap) and the perceived body scale. Changing body perception in real life depends on using tools such as a wheelchair or a long stick (Higuchi, Cinelli, Greig, & Patla, 2006; Higuchi, Cinelli, & Patla, 2009). Here, in order to understand the effects of body scaling on the affordance of pass through-ability and reachability, we conducted a virtual reality and a simulation study. Participants were assigned to different virtual shoulder widths scaled to their real size (narrow, normal and wide). In the experiment, they were asked to walk naturally to pass through an aperture without colliding and reach a target on a table. The success rate of passing through an aperture and the speed were similar in all conditions, which implied that participants adapted their virtual bodies. We also showed that participants were closer to the target when assigned narrow compared to a normal-size shoulder, suggesting that participants thought their body became smaller, so they moved closer to the target. In order to control the adaptation for conditions, we also conducted a perceptual judgement experiment. Also reflected in the perceptual judgements, participants with narrow virtual shoulders thought that they had smaller shoulder width, an effect not observed in the wide shoulder condition, which together demonstrate an asymmetry in the effects of body scaling.
Experience and insight under time pressure :|a study with race game
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2022., 2022.) Yalınkılınç, Duygu.; Ayhan, İnci.; Giritligil Kara, Ayça E.
In this paper, we experimentally study the effects of time constraints on learning efficient planning when subjects need to make sequential decisions. The subject is explored by utilizing a game theoretical tool called Race Game. In the context of race game efficient planning is achieved through backward induction which is considered to be a criteria that constitutes the ultimate rationality. Earlier studies demonstrated deviations from prescriptions of backward induction methodology, however more recent work demonstrated that subjects’ convergence to backward induction reasoning. Based on those studies, we examine whether and how time constraints affect learning backward induction methodology. We explore these questions by investigating subjects’ errors and response times in three different experimental time constraint conditions. The results indicate that time constraints, indeed, lead subjects to commit to more errors. Surprisingly, however, the solution process of subjects demonstrate a backwards order, resembling a convergence to using backward induction algorithm. The implications of this study may be beneficial for understanding how individuals learn effective planning and how deadlines should be set, for instance in the context of education and management.
Interaction between cyberbodies and cyberspace :| the effect of avatar abilities on affordance perception in virtual reality
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2019., 2019.) Akkoç, Naciye Tuğçe.; Ayhan, İnci.; Uğur, Emre.
The possible actions that we can perform with an object are determined by the capabilities of the human body. Then, if we could change the body, would it create new action possibilities for us? In this study, we examined the effect of altered abilities on the perception of potential actions for a given object — affordance perception. Objects with handles are known to potentiate the afforded action. Participants tend to respond faster when the handle is on the same side as the responding hand in a bimanual speed response task (Tucker & Ellis, 1986). In the first experiment, we replicated this effect in a Virtual Reality (VR) setting by manipulating the handle orientation and distance of the object with an intermediate level. In the second experiment, we showed that this effect was influenced by the avatar (a 3D representation of the body and its movements in VR) which was manipulated by two different hand types (able hand, i.e., able to grasp vs. restricted hand, i.e., not able to grasp). The division of the data collection into action planning and action execution created a valuable insight. Specifically, during action planning, the affordance effect was significantly stronger for the restricted hand. One explanation for this is that fewer action possibilities provided the restricted hand an advantage in processing time. During action execution, on the other hand, the affordance effect was reversed. This reversed effect is rarely found in the literature. In this case, it may be due to the ongoing action planning during action execution. The results were examined from a multidisciplinary perspective, together with a discussion on the implications for VR applications.
Interactions of body representations in rubber hand illusion and tool-use paradigms
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in Social Sciences, 2022., 2022.) Erkent, Mahmut Alp.; Ayhan, İnci.; Uğur, Emre.
In neuropsychological literature, numerous case studies suggest two separate body representations in the brain; one for perception, called the body image, and one for action, called the body schema. Rubber hand illusion and tool-use paradigms have been used frequently to investigate these body representations, respectively. Although these experimental paradigms are thought to affect different body representations, interactions between them are inevitable, considering the common sensory modalities targeted by the techniques used for measuring their effects. Still, there has been minimal overlap between these related fields of study. In this thesis, we combined these paradigms in a novel experimental setup and comparatively examined the resulting changes in body representations. Specifically, after a tool-use task where subjects actively used a grabber tool with their right hand to move cubes close to or away from their body, we observed an increase in the metric representation of the right forearm length depending on the length of the tool used. Subsequently, the “tool-holding” rubber hand illusion also increased the forearm length representation if the subject saw a longer tool held by the rubber hand. Follow-up experiments showed that this effect in rubber hand illusion depends on prior active use of the tool, embodiment of the observed hand and tool, and a length disparity between the held and observed tools during RHI. Overall, these results reveal for the first time that the representation of forearm length, a component of body schema, can be modified through changes in body image.
Neural and cognitive underpinnings of trustworthiness in the prefrontal cortex via optical brain imaging
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2019., 2019.) Bilik, Ali Taylan.; Ayhan, İnci.; Çakar, Tuna.
Human face has been considered to be an indicator of various attributes including attractiveness, calmness, and trustworthiness. Even a single look for a short duration might have an influence on one’s attitude. This empirical study aimed to understand the neural correlates of trustworthiness judgments on face photos via an optic brain imaging (fNIRS) method. The experimental design has been developed to categorize the presented photos after watching them for 4000 milliseconds. The responses were collected within a 3-point Likert scale. The obtained findings indicate that there is a significant level of neural activation difference between positive and negative responses among a specific optode (Optode-3). Moreover, there are also significant levels of neural activation differences for the neutral responses versus others among 3 optodes (Optodes 12, 14, and 16). The results were also controlled regarding the saliency levels of the photos as well as the emotional states of the individuals in the photos via facial activation coding analysis. Overall results imply that trustworthiness level might be understood at a certain level.
Sensorimotor interaction and time perception: An empirical study and a philosophical discussion
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2018., 2018.) Özbağcı, Duygu.; Ayhan, İnci.; Thorpe, Lucas.
Time perception is a crucial aspect of experiencing and acting upon the world. This thesis is composed of an empirical part, where the potential interactions between action and visual time perception are studied using psychophysical methodologies and a discussion part, where the results are discussed within a philosophical framework. The general procedure of the experiments includes a comparison between the visuomotor and passive visual observation conditions. The findings show that the perceived durations in the visuomotor conditions are underestimated. It is also demonstrated that the action induces a reduction in the perceived speed. It is claimed that the effects reported here might be modulated in the dorsal route. In fact, it is demonstrated that action-induced duration compression disappears using isoluminant stimuli. This provides further evidence that the locus of these effects should be somewhere, where the neurons are sensitive to luminance-modulation and temporal change. In a final control experiment, it is shown that color discrimination performance is not influenced by the execution of a concurrent motor act, which together implies that attentional factors cannot explain our main results. Broader indication of empirical studies is that the dorsal route has a principle role in the timing of visuomotor sequences. These results support the current philosophical stand that temporal consciousness is both (i) embodied; the body’s actions and states have an influence on the perceived time, and (ii) extended; the external information has direct contributions to the perceived time.
Temporal experience :|perception and action dynamics
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2019., 2019.) Kurtcan, Ayşe Melisa.; Thorpe, Lucas.; Ayhan, İnci.
This thesis is composed of an empirical study and a philosophical discussion on the influence of temporally altered feedback adaptation in response to willful actions upon the dynamic perceptual character of experience. In the former, the effects of delayed visual feedback adaptation on temporal integration of different perceptual features (such as color or motion direction) are studied using psychophysical methods based on previously shown perceptual order reversal of casual action and perceptual outcome after a delay adaptation (Stetman et al., 2006). Whereas in the latter, the philosophical background and the implications of our results on temporal experience are evaluated in light of current philosophical theories. We show that visuo-motor temporal recalibration elicited with respect to motion direction change in response to a voluntary causal action results in reduced apparent asynchrony between dynamic visual features of moving dots such as change in colour and motion direction previously observed by Moutoussis and Zeki (1997). Further experiments using a passive feature-correspondence task following an active recalibration phase revealed that this effect is attributable to voluntary action execution. Our claim is that the ongoing perceptual information is temporally regulated based on functional interpretation in respect of its causal history in action - perception loop which is triggered by the executive command. Predictive coding is suggested as the only model which fulfills these two characteristics: (i) dynamic recalibration of the temporal relations between voluntary action - sensory outcome (ii) cognitive interpretation of the functional content based on previously acquired causal relations.
The effects of smooth pursuit eye movements and abutting pattern motion on luminance contrast sensitivity
(Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2021., 2021.) Alaşhan, Didem.; Ayhan, İnci.; Uğur, Emre.
Spatiotemporal context alters the visibility. The detectability of a low-contrast luminance-modulated sinusoidal target abutting a high-contrast drifting grating is impaired when the two stimuli are out-of-phase, suppression being strongest at the leading than at the trailing edge of motion. This effect was attributed to the predictive signals (Roach, 2011) or a spatial summation process and inhibitory motion deblurring occurring at the trailing edge (Arnold, 2014). In the previous studies, however, eyes were steady and the grating envelopes were stationary. It was shown that smooth pursuit eye movements influence the luminance sensitivity in a directionally selective manner. To gain a better understanding of the phase dependent modulation of contrast sensitivity, I conducted a set of experiments, where the contextual modulation was investigated in the presence of smooth pursuit to examine the effects of pursuit velocity, directional congruence between the pursuit trajectory and the drifting gratings, and the contrast-dependency. Results indicated that the phase-dependent modulation occurs both at the leading and at the trailing edge under the fixation, although in different magnitudes contradicting the predictive model. During pursuit, the size of modulation at the leading edge depends both on the pursuit velocity and the directional congruency. Additionally, the magnitude of the modulation is contrast-dependent only at the leading edge. These findings are consistent with neither the predictive nor the spatial summation account but rather suggest different underlying mechanisms at the leading and trailing edges, which may be modulated by feedback connections from higher-order sensorimotor areas.

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