1st Lesson - Perception Theory

PERCEPTION THEORY AND PSYCHOLOGY OF FORM

Course Overview

  • Instructor: Prof. MARTA CALBI, IED (Year 2025/2026)

  • This course introduces basic concepts of visual perception and the physiology of vision, providing essential tools to understand the meaning of "to see."

  • Focus on:

    • Perception of the human figure (faces, bodies, clothing)

    • Interaction within the fashion system

  • Central module on color perception and its psychological applications:

    • Influence of chromatic choices on visual communication, styling, atmosphere, and identities.

  • Case study of the mask:

    • Highlights how clothing and accessories shape identity construction.

  • Complementary iconographic research rooted in visual culture, including references to ethonography and first-person perspectives.

  • Integration of case studies from fashion, art, and media to illustrate perception and representation across cultural contexts.

Exam Structure

  • The final exam consists of two mandatory parts:

    1. Oral Interview: Evaluates preparation, understanding of course materials, and participation in discussions.

    2. Project Presentation: To be delivered before Lesson 8 of the course.

Conceptual Framework

Understanding Visual Perception

  • What does "to see" mean in fashion and visual communication?

    • Exploration of visual language through fashion showcasing trends (e.g., Balenciaga's Fall/Winter 2022 collections).

Sensation and Perception

Definitions

  • Sensation:

    • The ability to detect stimuli (e.g., sound, light, taste) activating sensory channels, transforming detection into personal experience.

  • Perception:

    • The subsequent interpretation and meaning-giving process of detected sensations.

Study Methodologies

  • Psychophysics:

    • Defines the quantitative relationships between physical events and psychological experiences.

    • Key Figures:

      • Gustav Theodor Fechner (1801-1887): Developed formal descriptions connecting energy and sensation.

      • Ernst Weber (1795-1878): Conducted experiments on object weight, leading to foundational concepts in psychophysics.

Key Concepts in Psychophysics

  • Just Noticeable Difference (JND):

    • The minimum difference in sensation required to detect a change in physical weight.

  • Differential Threshold:

    • The minimal change in stimulus needed for a JND.

  • Weber's Law:

    • Expressed mathematically as
      \Delta\Phi = K \times \Phi

    • States that the ratio of the increment threshold to the background intensity is a constant.

  • Fechner’s Law:

    • Relationship between stimulus intensity (\Phi) and sensation (S) is logarithmic, represented as S = c \log \Phi

    • As intensity increases, larger changes in stimulus are needed to produce detectable differences in sensation.

  • Absolute Threshold:

    • Minimum intensity of a stimulus detectable by the observer.

Methods of Measuring Sensation

  1. Method of Constant Stimuli:

    • Involves various stimuli of different intensities to identify the threshold at which detection is 50% likely.

  2. Method of Limits:

    • Presenting stimuli in increasing or decreasing order to determine perception thresholds.

  3. Method of Adjustments:

    • Subjects adjust the stimulus intensity until detection occurs.

  4. Method of Magnitude Estimation / Stevens' Power Law:

    • Participants numerically rate the perceived intensity of stimuli.

    • Described by S = c\Phi^b, indicating that perception does not scale linearly with physical intensity.

Signal Detection Theory

  • Developed by Green & Swets (1966):

    • Quantifies how observers respond to signals amidst noise.

    • Measurements include:

    • Sensitivity (d′): Ability to distinguish between signal and noise.

    • Response Criterion (β): Threshold for deciding if a signal is present.

Neuroscience and Neuroimaging Techniques

Structural Techniques

  • Allows observation of brain anatomy:

    • MRI (Magnetic Resonance Imaging)

    • CT (Computed Tomography)

Functional Techniques

  • Analyzing brain activity in real-time:

    • fMRI (Functional Magnetic Resonance Imaging)

    • PET (Positron Emission Tomography)

    • EEG (Electroencephalography)

    • MEG (Magnetoencephalography)

Computational Models of Perception

  • Explains how the brain processes visual information akin to computing:

    • Key Components:

    • Input: Visual stimuli (color, shape, pattern)

    • Processing: Based on rules, prior knowledge, and context.

    • Output: Visual interpretation and perception of style/identity.

  • Applications in Fashion:

    • Analysis of trends and color perception in fashion images.

Bayesian Models of Perception

  • Explain perception as a probabilistic inference process:

    • Combines prior knowledge and current visual signals to update hypotheses about perception.

    • Steps:

    1. Hypothesis Creation

    2. Stimulus Processing

    3. Belief Updating using Bayes' Theorem

    4. Surprise Reduction

  • Applications in Fashion:

    • Predicting styles and identities based on visual cues.

Neural Networks

  • Framework to understand sensory system development:

    • Composed of computational units (neurons) organized in layers (INPUT → HIDDEN → OUTPUT).

    • Uses feedback adjustments to improve performance over time.

The Nervous System

Overview

  • Comprised of:

    • Peripheral Nervous System

    • Central Nervous System (Brain and Spinal Cord)

  • Brain Anatomy:

    • Divided into hemispheres, each containing lobes: frontal, parietal, temporal, occipital.

Functional Areas of the Cerebral Cortex

  • Visual Area: Image recognition and perception.

  • Olfactory Area: Smelling.

  • Sensory Area: Sensation from muscles and skin.

  • Motor Function Area: Initiation and control of voluntary muscles.

Physiology of Vision

The Physics of Light Waves

  • Light is comprised of particles called photons, describable as electromagnetic waves.

  • Components of the Eye:

    • Cornea, Iris, Lens, Retina, Fovea, Pupil, Blind spot, Optic nerve.

Photoreceptors in the Retina

  • Cones:

    • Responsible for vision under bright conditions and color perception, concentrated in the fovea.

    • Three types based on photosensitive pigments: Blue, Green, Red.

  • Rods:

    • Enable vision in low light conditions and peripheral vision.

Light Transduction Process

  • Photoreceptors undergo chemical changes upon capturing light, resulting in neural signaling that creates visual sensations.

    • Visual Pigments: Comprised of proteins and chromophores that absorb light.

Visual Pathway

  • Flow of visual information to the central nervous system involves the integration of visual processing streams:

    • Dorsal Stream: Responsible for spatial processing (location, movement).

    • Ventral Stream: Involved in object processing (color, texture, shape).

Fashion as a Perceptual Medium

  • Fashion constructs perceptions and messages, as demonstrated through iconic designs by various designers such as Irving Penn and Alexander McQueen.

Conclusion

  • The course encapsulates the intricate relationship between perception, fashion, and identity, through the lens of visual culture and neuroscience.