Theses

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İrem Tuncel, The Effect of Material Sound on Material Perception through Turkish Sound Symbolic Words, 2025

• Research has shown that a subset of sound-symbolic words (SSWs), onomatopoeic words (e.g., splash) that imitate sounds, are strongly associated with perceived material properties. Moreover, semantic dimensions derived from visual and haptic materials align with those extracted from SSWs, indicating cross-modal consistency. In this thesis, natural material sounds and videos of everyday materials were to investigate material perception through SSWs. To select SSWs, in preliminary Study 1, participants wrote down their answers mimicking natural sounds. Following a letter frequency analysis for common phonetic patterns, SSWs including these phonemes are used in the main experiment. In Study 2, participants identified materials solely by listening to sounds representing materials, and high agreement responses were chosen. In the main experiment, materials were presented multiple times: across conditions of natural sound congruency and SSW congruency, and rated on SSWs. It is hypothesized that congruency between natural sound and SSWs would more strongly influence perception than visual congruency, predicting that audiovisual (AV) congruent stimuli would receive higher ratings for matching SSWs than AV incongruent stimuli. As expected, SSWs in the same dimensions with material videos got higher ratings on the congruent AV stimuli compared to incongruent AV stimuli. Furthermore, overall ratings between congruent and incongruent AV stimuli did not differ when SSWs were incongruent with material videos. However, for incongruent AV stimuli in certain material dimensions ratings increased for incongruent SSWs. These findings highlight the role of material sounds in perceived material characteristics and challenge the widespread notion of visual dominance in multisensory integration.

• Tuncel, İ & Dövencioğlu, D. N. (submitted) Audiovisual Material Perception: Language-Specific Effects on Multisensory Integration.

Yunus Emre Türkmen, Perceived Animacy from Global and Local Image Distortions, 2025

• Animacy perception is the ability to discriminate between visual stimuli as animate or inanimate. The effects of global shape structure and mid-level scales, such as symmetry, and curvilinearity on perceived animacy are highly studied; however, the relationship between local image distortion and animacy perception is lacking in literature. In Experiment 1, I morphed animate-inanimate pairs and asked participants to classify morphed visual stimuli as animate or inanimate within 150 milliseconds to observe the impact of overall global shape cues on perceived animacy. Although previous literature has shown that local distortions can create an experience of transparent layers (Dövencioğlu et al., 2018), the effects of these distortions on animacy perception are unknown. In Experiment 2, I investigated how local image distortions affect animacy perception through eidolons. Participants adjusted reach-grain parameters to distort the local disarray of 20 images and create equivalent appearance classes (eidolons). Parameter adjustments for the three modes ("underwater," "behind glass," or "animate") were significantly different from one another. As curvature increased, participants adjusted lower values for both parameters. In Experiment 3, a 2AFC experiment, participants judged the perceived animacy of symmetrical insect-like stimuli in their fiducial forms and nine equivalence classes. Again, the global curvature and perceived animacy increased together, and local curvature manipulations yielded idiosyncratic results. While these findings confirm that local distortions in the image can create transparent percepts, they also indicate associations between global and local shape cues and perceived animacy, suggesting that both contribute to the discrimination of animate from inanimate.

Öykü Göze Özdemir, The Role of Perceived Material in Associative Recognition of Familiar and Unfamiliar Objects, 2025, co-supervised by Assoc. Prof. Aslı Kılıç Özhan. 

• Previous research suggests that object features such as color or shape enhance memory processes, but none of them specifically focus on the material of objects, which is a crucial feature. This thesis seeks to understand how object features such as shape, material, surface texture, and reflectance influence the encoding and retrieval of objects in associative memory. Associative memory refers to how associations are formed across items either strategically, semantically, or perceptually. Specifically, I used a recognition task to understand the nature of associations formed when perceiving familiar and unfamiliar objects with congruent and incongruent materials. The stimuli in Experiment 1 contained three-dimensional (3D) model images of four familiar objects (jug, water glass, goblet, mug) rendered with four materials (wood, metal, glass, stone). The stimuli in Experiment 2 contained images of unfamiliar 3D models rendered with the same material categories as in Experiment 1. The stimuli in Experiment 3 contained images of one unfamiliar object rendered with seven texture categories (wood, metal, glass, stone, copper, plastic, and jelly) and two surface reflectance categories (matte, glossy). The findings revealed that recognition sensitivity (d’) was higher for material, shape, and reflectance congruent conditions than incongruent ones. There was no significant difference between material congruency and shape congruency as a memory facilitator in Experiment 1. On the other hand, for unfamiliar objects, the material feature was significantly better remembered than the shape and reflectance features. These findings shed light on the crucial role of the object material, complementing shape and reflectance, in associative recognition.

• Özdemir, Ö.G., Kılıç, A., Dövencioğlu, D. N. (submitted) Beyond Shape and Color: Material as a Cue in Associative Memory 

Fatma Kılıç, The Role of Prior Knowledge and Visual Cues on Perceived Softness, 2023

• Haptic perception is the active exploration of materials by touch. When exploring objects, we use stereotypical hand movements called ‘Exploratory Procedures’ (EPs, Lederman & Klatzky, 1987). These EPs are related to the specific material and task properties, such as rubbing a jersey to assess its softness. Softness of a material has been treated as a single dimension and in fact identified with compliance (Lederman & Klatzky, 1987; Baumgartner, 2013; Di Luca, 2016). However, it has recently been shown that perceived softness is multidimensional, and people use specific EPs for perceptual softness dimensions (Dövencioğlu et al., 2022). The aim of this thesis is to understand how much prior knowledge, and visual cues account for the specific EPs associated with softness dimensions. Are the EPs based on the prior knowledge of observations and information that is learned? Or do people infer material properties from the current visual information that they obtain from the material? In Experiment 1, how much prior knowledge and visual cues affect the softness judgments in the absence of haptic sensory input was investigated. Here, it was observed that there can be material- and adjective-specific differences between prior knowledge and visual cues. Experiments 2 and 3 aimed to understand how the appearance of EPs affects the softness perception of a material. It was found that a congruent EP that is correlated with the same dimension as the material yielded different ratings compared to an incongruent EP. This difference was observed partially for the adjectives that are semantically associated with the same dimension.

• Kılıç, F. & Dövencioğlu, D. N. (2024) Visual Softness Perception Can Be Manipulated Through Exploratory Procedures, Perception https://doi.org/10.1177/03010066241261772

Beyza Melis Hazır, The Effects of Language on Perceived Softness, 2022

• Perceived haptic softness of materials has been studied as a single dimension; however, it has recently been shown that it has multiple dimensions. Research on bimodal perception demonstrated the effect of sound frequency on perceived shapes, where people associate higher frequency sounds with angular shapes and lower frequency sounds with round shapes, known as the Bouba/Kiki effect. In this thesis the effects of onomatopoeic words, the words that mimic the sound they describe (e.g., şırıl şırıl, çatır çutur, etc.), were investigated on perceived material softness to test whether similar associations between onomatopoeic words and perceived softness also exist. Experiments were carried out using the onomatopoeic words in the written and the spoken form, and the materials in the video form. The two experiments using written and spoken onomatopoeic words report four softness related dimensions. The online experiment using written onomatopoeic words and material videos showed no significant results for the interaction effect of onomatopoeic words and materials. However, using spoken onomatopoeic words, the interaction effect was found to be significant for most of the pairings. Experiment with written onomatopoeic words conducted in a laboratory environment showed significant results for the effects of onomatopoeic words on perceived softness. There was no significant difference observed between the written and spoken modalities of onomatopoeic words, except for the main adjective Gelatinous. Hence, the obtained results are in line with previously reported findings, and support the hypothesis that onomatopoeic words have an effect on the perceived softness of materials.

• Nalbantoğlu, H., Hazır, B.M., Dövencioğlu, D.N. (2023) Selectively manipulating softness perception of materials through sound symbolism. Frontiers in Psychology. https://doi.org/10.3389/fpsyg.2023.1323873