Senses and Perception: Seminar Summaries 2025/2026
Development of Visual Perception
The development of visual perception is fundamentally rooted in the maturation of the visual system itself. During prenatal development, the basic patterns of the visual system are formed. However, at birth and through the first month of life, an infant's vision remains immature and blurred. Newborns primarily respond to moving objects and stimuli characterized by high contrast. Furthermore, their attention is notably drawn to objects with vertical symmetry, a preference largely attributed to the resemblance of such patterns to the human face.
In the period between the second and fourth months, children begin to maintain a steady focus on faces and objects. This stage is marked by the development of habituation, where the child learns to distinguish between familiar and novel stimuli, indicating early processes of learning and memory. By approximately the fifth month of age, a child's color perception begins to closely resemble that of an adult. Between the fourth and sixth months, ocular coordination improves significantly, which facilitates the development of stereopsis (depth perception). During this same interval, children become more proficient at differentiating an object from its background.
Visual acuity typically reaches adult levels between the sixth and ninth months. The development of crawling is a critical milestone during this time, as it further refines eye-body coordination and establishes vision as the primary means of navigating space. Additionally, infants develop the visual ability to recognize objects that are partially hidden, signaling the maturation of visual memory. Between the ninth and tenth months, visual perception begins to direct fine motor skills, and by the first birthday, vision is almost entirely integrated with motor functions. This work was presented by Maja Abramović, Katarina Peteš, and Ana Repac.
Questions & Discussion
On which stimuli do infants react most in the first month of life? When does a child begin to distinguish between familiar and new stimuli and develop depth perception? How does the development of vision contribute to the development of crawling, fine motor skills, and the recognition of hidden objects?
Facial Perception
Facial perception is a vital component of human cognition, and most individuals are highly successful at recognizing faces. Infants spontaneously direct their attention toward human faces from a very early age. Throughout a person's life, the ability to recognize a vast number of different individuals continues to evolve (Haxby et al., 2000). The recognition of familiar faces relies on a comparison between the face currently being viewed and representations stored in memory (Bruce & Young, 1986).
This cognitive process involves a specialized system in the brain that first detects a face as a distinct category of stimulus. It then analyzes specific characteristics to allow for identification and categorization. This occurs holistically, meaning the face is perceived as a unified whole rather than a sum of parts, which enables rapid and efficient recognition (Tsao & Livingstone, 2008). The neurological basis for this includes a network of specialized areas: the occipital area for early analysis, the fusiform face area (FFA) for identity analysis, and the superior temporal sulcus (STS) for the analysis of expressions and gaze (Kanwisher et al., 1997).
Faces provide essential information regarding identity and emotions. Facial expressions play a crucial role in non-verbal communication, allowing for the quick recognition of other people's feelings and intentions. Deficits in facial processing can lead to significant difficulties, such as prosopagnosia, a disorder of face recognition that can be either acquired or congenital (Grüter et al., 2008). This work was presented by Ema Fratrić, Elizabeta Ivančević, and Monika Krznar.
Questions & Discussion
What is prosopagnosia? What are the key brain areas involved in face perception? What role do facial expressions of emotion play in social communication?
Visual Disorders
Visual disorders are common symptoms of diseases affecting the eye, the orbital cavity, the visual pathway, and the central nervous system (Maciag et al., 2024). These disorders can also involve patterns of perceptual changes that may not be caused by pathological conditions within the eye itself (Zhou et al., 2022). Common visual disorders include myopia, hyperopia, astigmatism, glaucoma, amblyopia, and intermittent exotropia.
Short-sightedness, or myopia, is a condition where the focal point of light falls in front of the retina, resulting in a blurred retinal image and poor distance vision. Conversely, far-sightedness, or hyperopia, occurs when the focal point falls behind the retina, causing poor near vision (Domijan & Valerjev, 2026). Astigmatism is a condition in which parallel light rays passing through the cornea do not converge at a single point on the retina (Gurnani & Kaur, 2023). Glaucoma is a disorder characterized by elevated intraocular pressure, which can lead to permanent vision loss due to damage to the retina and the optic nerve (Domijan & Valerjev, 2026).
Amblyopia is a developmental visual disorder caused by abnormal visual experiences during early life (Zhou et al., 2022). Intermittent exotropia is characterized by occasional exodeviation, which is the outward turning of one or both eyes toward the temples; this is mostly manifested when the person is fixing their gaze on distant objects (Kaur, 2025). This work was presented by Marta Babok, Laura Gauš, and Lana Curić.
Questions & Discussion
What are visual disorders and what do they include? Name some visual disorders. What is the difference between short-sightedness and far-sightedness?
Geometric Illusions
Geometric illusions are perceptual phenomena that arise from a discrepancy between the objective physical characteristics of a stimulus and the observer's subjective visual perception. Scientific interest in illusions grew in the second half of the 19th century, largely due to Johann Joseph Oppel, who introduced the term "geometric-optical illusions" to the literature. Several general terms are used to describe these illusions: the visual field (everything visible at a given moment), the target (the specific feature being examined), the context (the rest of the visual field), and the inductor (the part of the context that varies to induce changes in the perception of the target).
Geometric illusions are categorized into illusions of size, shape, position, and tilt. Famous examples include the Müller-Lyer, Ebbinghaus, Münsterberg, Ponzo, Zöllner, and Delboeuf illusions. Theoretical explanations for these phenomena are divided into metric aspects (including contrast, assimilation, reduction, expansion, and the attraction of parallels) and orientation principles (such as regression toward right angles and orthogonal expansion). More recently, Gestalt effects have also been highlighted.
In the context of psychophysical research, "Type 2" tasks are often employed to measure the magnitude of a perceptual illusion—quantifying how much the subjective experience deviates from the physical properties of the stimulus. Research has also demonstrated that geometric illusions are perceived not only by humans but also by animals with laterally placed eyes, such as birds. This work was presented by Manuela Batelja, Luana Orbanić, and Laura Sakač.
Questions & Discussion
What are geometric illusions and how do they arise? How are the principles that explain illusions divided? Describe how geometric illusions are researched in psychophysics.
Multistability: Perception of Ambiguous Figures
Perceptual multistability is a phenomenon in which a single, physically unchanging sensory stimulus results in spontaneous alternations between two or more perceptual states. It is important to distinguish between reversible figures (the ambiguous visual patterns themselves) and the process of reversibility (the subjective experience of oscillating between interpretations). Famous examples include the Necker cube, Schröder's stairs, and the "My Wife and My Mother-in-Law" image, where the same visual template can depict either a young woman or an old lady.
Another significant example is binocular rivalry, a specific form of multistability where the brain, faced with different images in the left and right eyes, alternately selects one image for consciousness while temporarily suppressing the other. Traditional explanations attributed these shifts to exhaustion or "satiation" within the visual system, but modern research emphasizes the role of attention, voluntary control, and prior experience. These findings suggest that perceptual changes are not passive responses but active processes modified by central brain structures involved in planning and behavior.
During these events, the brain undergoes a process called "internal foraging," where it selects what and how to perceive by searching for relevant or informative stimulus parameters. The dynamics of these alternations are influenced by subjective variables like mood and voluntary control, and the process can be significantly accelerated through practice. Neurobiologically, higher cognitive mechanisms in the frontal and parietal cortex play a key role in selection and interpretation, while the primary visual cortexes (V1 and V2) remain relatively stable. This work was presented by Klara Filipović, Kristina Vukovojac, and Emily Zustović.
Questions & Discussion
What are reversible figures? What does the process of "internal foraging" entail? Which brain areas play a key role in the multistability of perception?
Speech Perception
Speech perception is the complex process by which a listener receives, processes, and interprets acoustic language signals to understand spoken words and sentences. This involves interaction between auditory, cognitive, and linguistic mechanisms. Although speech is a continuous acoustic signal, humans perceive it as discrete units such as phonemes, syllables, and words. A key phenomenon is categorical perception, where continuous acoustic differences are sorted into distinct phonological categories.
The meaning of a sentence, previous experience, and expectations can significantly influence speech interpretation. The brain actively uses available information to fill in gaps or ambiguities in the signal, such as in noisy environments. This phenomenon is known as perceptual restoration, proving that speech perception is not a passive process. Research indicates that areas in the left hemisphere, particularly the temporal lobe, are crucial for this function.
The development of speech perception begins in infancy. Initially, infants can distinguish a wide range of sounds from various languages, but over time, they specialize in their native language, highlighting the importance of linguistic exposure. This work was presented by Nela Bojanić, Gabrijela Kozelički, and Karmen Maršanić.
Questions & Discussion
What is the name of the phenomenon where the brain fills in missing parts of speech? Which lobe of the brain is involved in speech perception? What is categorical perception?
Hearing Disorders
The process of hearing is a complex chain of energy transmission. Any disruption in this chain results in hearing loss, which is the partial or total inability to perceive sound, diagnosed via a clinical audiometric threshold. There are three main types based on the location of the damage. Conductive hearing loss occurs due to obstacles in the outer or middle ear (e.g., otosclerosis) that block sound paths. Sensorineural hearing loss is caused by damage to sensory cells or the auditory nerve, often due to medications, noise, or aging (presbyacusis), and includes Meniere's disease.
A specific form is sudden hearing loss, defined as a rapid drop of at least within three days, with causes ranging from infectious and vascular to immunological or tumor-related. Mixed hearing loss is a combination of conductive and sensorineural types. Beyond organic causes, functional hearing loss occurs despite the absence of organic abnormalities, and central disorders (such as auditory agnosia) make it difficult for the brain to interpret sounds despite normal ear function. The most severe form is deafness, defined as thresholds over , where only extremely loud sounds can be heard. Deafness is classified as prelingual or postlingual based on language acquisition.
An early indicator of damage is often tinnitus, the conscious perception of sound without an external stimulus. Hearing loss affects all ages and can lead to difficulties in education, language, and cognitive status, often resulting in depression and social withdrawal. Solutions include surgical procedures, cochlear implants, rehabilitation, and hearing aids. This work was presented by Tea Krešić, Leonarda Kutarčić, and Elena Šišmanović.
Questions & Discussion
What is the fundamental difference between conductive and sensorineural hearing loss according to the site of damage? What is tinnitus and what can it predict? How is deafness defined and how can it be divided?
Music Perception
Music perception is a complex, multidimensional sensory experience. Listening to music involves the perception of frequency, duration, timbre, and volume, as well as melody, rhythm, tempo, and meter. Various neural structures have unique roles in creating and integrating these sensations. Beyond the basic structures of the auditory system, specific neural circuits interpret different musical features. Higher neural structures integrate these stimuli to form a complex perceptual experience.
Auditory grouping principles—such as sound localization, similarity in timbre and pitch, temporal proximity, the law of good continuation, and prior experience—help the brain organize sounds into coherent sequences. Dynamic theories explain the biological basis of how music influences complex cognitive functions like emotional experience and learning. Key structures include the limbic system, responsible for emotional reactions to music, and the prefrontal cortex, which analyzes complex musical patterns. Two opposing phenomena in this field are amusia, a neurological inability to process musical elements, and absolute pitch, the ability to recognize the pitch of a tone without a reference point. This work was presented by Sara Cvijanović and Irma Vidović.
Questions & Discussion
List some of the characteristics of music we perceive while listening. Explain the role of the limbic system in music perception. What is absolute pitch, and what is amusia?
Sensory Integration
Sensory integration is the process by which the brain combines information from different sensory systems to form a unified perception of the environment. The brain evaluates the reliability of each sensory modality and prioritizes those providing the most accurate information (Ernst & Banks, 2002). Research shows that senses are not processed in isolation but are integrated through multisensory processes that combine previous experience with current data.
Neural synchronization allows for the connection of information across different brain areas. The thalamus acts as an active integration center involved in shaping perception and consciousness, rather than just a relay station (Florio, 2025). There are three rules of sensory integration: the spatial rule (integration is stronger when stimuli come from the same location), the temporal rule (simultaneous stimuli have a greater effect), and the rule of inverse effectiveness (integration is more pronounced for low-intensity stimuli that barely reach the threshold individually) (Domijan & Valerjev, 2026).
For example, in a quiet room, hearing is sufficient for speech understanding, but in noise, visual cues like lip-reading become significantly more helpful (MacLeod & Summerfield, 1987). This work was presented by Katarina Prša, Rea Sabol, and Dorotea Stjepčević.
Questions & Discussion
What is sensory integration? What is the role of the thalamus in sensory integration? What are the three rules of sensory integration?
Selected Chapters from Pain Perception
Pain perception is a complex psychological and neurobiological process influenced not only by physiological stimuli but also by cognitive, emotional, and social factors. Contemporary research emphasizes a biopsychosocial approach, where the subjective experience of pain is shaped by bodily signals, mental processes, and social context. Social support, empathy, and positive relationships can alleviate pain, while social isolation or discrimination can increase sensitivity.
Pain can also occur as a reaction to someone else's suffering (empathetic pain). A unique phenomenon is the phantom limb, where an individual feels pain in a body part that is no longer there after an amputation. This is caused by neuroplastic changes in the brain, particularly the somatosensory cortex, where the representation of the missing limb may be "taken over" by neighboring regions. Another significant phenomenon is the placebo effect, where the expectation of a treatment's effectiveness leads to pain reduction. This concept, where cognitive states directly influence perception, is called cognitive penetration. This work was presented by Anđela Marasović, Lucija Pavlović, and Vanesa Vukas.
Questions & Discussion
How can the presence of other people or social support affect the intensity of pain a person experiences? What role of the brain in creating the sensation of pain is indicated by the phantom limb phenomenon? How does the placebo effect confirm that pain perception is not exclusively a physiological process?
Synesthesia
Synesthesia is a phenomenon where stimuli (inductors) trigger additional involuntary and automatic experiences (concurrents) that do not manifest physically. Synesthetes experience this daily, usually starting from early childhood. There are two types based on the nature of the inductor: sensory (synesthetic perception) and conceptual (synesthetic conception). In sensory synesthesia, concurrents are triggered by sensory stimuli, while in conceptual synesthesia, they are triggered by thinking about certain concepts.
Forms of synesthesia include connections between words and tastes, tastes and shapes, music and colors, or numbers and spatial arrangements (e.g., grapheme-color). Synesthesia can be developmental or acquired. Developmental synesthesia likely stems from genetic differences and atypical neurological development. Acquired synesthesia, which may only involve synesthetic perception, can be caused by brain injury, sensory deafferentation (interruption of sensory input), or drug use.
Neural research shows strong connectivity between brain areas responsible for processing inductors and concurrents (e.g., intraparietal sulcus activation in shape-color synesthesia). Studies also indicate increased density of gray matter and white brain fibers in regions like the fusiform gyrus. This work was presented by Katja Knežević, Andrea Sinovec, and Rea Smogor.
Questions & Discussion
What are the two types of synesthesia according to the nature of the inductor and how do they differ? Increased density of which brain matter is often associated with synesthesia? What factors can cause acquired synesthesia?
Perception of Time
Time perception is the ability to estimate the duration and sequence of events, which is essential for planning, behavior coordination, and decision-making. Since there is no specific sensory system for time, the subjective experience of time relies on a network of neural and cognitive systems. Models explaining this include the "internal clock" models, which suggest a specialized timing mechanism, and "intrinsic" models, which view time as a byproduct of general brain activity.
The neurological basis includes the basal ganglia, cerebellum, cortical areas, and the dopamine system, which regulates the subjective sense of duration. Cognitive factors like attention and working memory, as well as emotional states, significantly impact perception. High arousal can lead to the overestimation of duration, while intense focus can cause time to be underestimated. Distortions occur during boredom, fear, or pleasant activities. This work was presented by Marta Kardum, Lucia Radanović, and Marija Vidović.
Questions & Discussion
Explain the difference between the internal clock model and intrinsic models of time perception. Which brain structures are associated with time perception in the context of its neural basis? Why can the subjective experience of time deviate significantly from objective duration, and in which situations are these distortions particularly pronounced?
Echolocation
Echolocation is an active process used by species such as bats, whales, and small mammals like rats and shrews for spatial orientation when vision is ineffective. It works by producing high-frequency sounds and detecting their echoes. By comparing the interval between the sound and its echo, animals create a mental map of their space. Bats produce ultrasonic waves in the larynx and detect echoes with mobile ears to locate prey while flying. Dolphins produce waves in nasal cavities and direct them via fatty tissue on the head.
While echolocation does not naturally exist in humans, research shows that blind individuals can develop a similar ability through training, using tongue "clicks" or finger snaps to navigate. Even sighted people can achieve this effect with practice, though blind individuals are generally more advanced. This work was presented by Tizian Leon Andijranić, Mateo Luketić, and Jan Zajec.
Questions & Discussion
What is echolocation? How can blind people achieve an effect similar to echolocation? What is the evolutionary importance of echolocation?
Pheromones
Pheromones are chemical molecules that facilitate communication between members of the same species (Domijan & Valerjev, in press). They spread through air or water and act like external hormones. They are used for attracting partners, marking territory, or signaling danger. Pheromones are divided into releasers (triggering immediate behavioral reactions) and primers (causing long-term physiological changes).
Releaser pheromones include alarm, dispersion, and aggregation pheromones. Alarm pheromones warn a group of danger, dispersion pheromones mark territory, and aggregation pheromones attract individuals to food or habitats. Sex pheromones are a type of aggregation pheromone; for example, female silk moths secrete bombykol, which males detect from great distances. In mammals, pheromones are received via the vomeronazal organ. In humans, this system is reduced, making the existence of functional human pheromones questionable. Research on menstrual synchronization (MHC) or sexual attraction through pheromones has largely remained unconfirmed (Wyatt, 2020; Havliček et al., 2020). Practically, pheromones are used in agriculture to trap pests, like the grapevine moth, reducing insecticide use (Barić et al., 2021). This work was presented by Dora Petričević and Nina Krog.
Questions & Discussion
Define pheromones. How are pheromones divided? What is the role of pheromones?
Biological Compass
The biological compass, or magnetoreception, is the ability of animals to detect and use the Earth's magnetic field for orientation and navigation. Animals use two characteristics: polarity (the polar compass) and the inclination of magnetic field lines (the inclination compass). This was first researched in the mid-20th century and is especially vital for migratory species, such as birds, that travel long distances where environmental cues vary.
Besides birds, this ability is found in salmon, moles, turtles, amphibians, and invertebrates like insects and mollusks. Animals use magnetic data to follow migration paths and return to birthplaces. The mechanisms are not fully understood, but hypotheses involve cryptochromes and quantum processes of radical pairs (studied in birds), as well as ion channels in cell membranes. This work was presented by Doriana Biondić and Laura Hirsch.
Questions & Discussion
What is the biological compass? What are the two characteristics of the Earth's magnetic field that animals use for orientation? Why is the biological compass important for migratory species?