Lecture 11 - Colour Vision

Sensation vs. Perception

Sensation:

  • Definition: Sensation is the initial process of converting external physical stimuli (like light, sound, and touch) into electrochemical signals that are understood by the nervous system, allowing individuals to experience their environment.

  • Evolution: Over time, organisms have developed complex sensory mechanisms, which enable them to effectively process these signals, thus enhancing their chances of survival. Different species exhibit varying sensitivities to sensory stimuli based on their ecological needs.

Perception:

  • Definition: Perception refers to the cognitive process that interprets and organizes these electrochemical signals into meaningful patterns. It involves higher-level processing influenced by an individual's experiences, expectations, and cultural background.

Lightness Constancy

  • Concept: Lightness constancy is the phenomenon where the perceived lightness of surfaces remains relatively constant under changes in illumination. This ability allows individuals to recognize objects irrespective of the lighting conditions, contributing to accurate object recognition in diverse environments.

Weeks 6-10 Lecture Schedule

  • Week 6:

    • Lecture 11: Colour Vision

    • Lecture 12: Spatial Vision

  • Week 7:

    • Lecture 13: Temporal Vision (Motion) and Depth

    • Lecture 14: Understanding the Visual World

  • Week 8:

    • Lecture 15: Face Perception

    • Lecture 16: Hearing and Speech

  • Week 9:

    • Chemical Senses: Smell and Taste

    • Somatosensation and Proprioception

  • Week 10:

    • How the Senses Work Together

    • Individual and Cultural Differences in Perception

Lecture 6: Colour Vision

  • This lecture covers fundamental aspects of colour vision and its relationship to spatial perception, demonstrating how both fields intertwine in effective visual processing.

Dimensions of Colour

  • Hue: The quality of a colour that allows it to be classified as red, green, blue, etc.

  • Saturation: Refers to the purity or intensity of the hue; high saturation means vivid colours, while low saturation results in muted or pastel colours.

  • Brightness: The perceived intensity of light that reaches the eye, an essential factor in how we differentiate between colours under various lighting conditions.

Trichromatic Colour Vision

  • Historical Insights:

    • Palmer (1777), Young (1802), and von Helmholtz (1852) proposed foundational theories about colour perception, suggesting that human vision relies on three types of cone cells sensitive to distinct ranges of wavelengths, corresponding mainly to red, green, and blue light.

Visual Diversity

  • The visual world encompasses a vast spectrum of colours, which play significant roles in communication and emotional expression. Variation in colour perception across individuals and cultures underscores the complexity and diversity of human visual experience.

Colour Aftereffects

  • Aftereffects, such as the lingering perception of colour after staring at a vibrant hue, illustrate the dynamic nature of our visual processing, showcasing how adaptation influences perception.

Opponent-Process Theory

  • Proposed by Ewald Hering (1892), this theory suggests that the interpretation of colour involves three pairs of opposing colours (red/green, blue/yellow, black/white), facilitating a more nuanced understanding of how visual signals are processed beyond simple receptor responses.

Colour Channels

  • Colour Vision Channels: These include both achromatic (colours devoid of hue) and chromatic (coloured) channels. The interplay between these channels is crucial for the richness of human visual experience.

  • Colour Pairs: Key pairings such as Red/Green and Blue/Yellow are fundamental in understanding contrasting colour perception and visual harmony.

Colour Mixing

  • Isaac Newton (1672): His exploration of light demonstrated that white light is a combination of all colours in the spectrum, and through additive mixing, can recreate white light, an essential principle in both physics and visual arts.

Additive Colour Mixing

  • This process pertains to light sources where the addition of light in different colours results in increased energy and brightness; a foundational concept for digital displays and lighting.

Mixing Paint/Pigments

  • Primary Colours: Yellow, Red, Blue. These are the base colours that can be combined to create a wide range of secondary and tertiary colours.

  • Secondary Colours: Created by mixing primary colours (e.g., Yellow + Blue = Green), showcasing the transformative nature of colour blending.

Subtractive Colour Mixing

  • Involves pigments where mixing colours results in decreased light energy, illustrating the physics of colour in materials. This principle is critical in art, design, and printing industries.

Real-World Colour Application

  • Understanding colour theory has practical applications in various fields, such as art, design, psychology, and marketing, influencing how colours are used strategically for desired responses.

Colour Contrast

  • Simultaneous Colour Contrast: Developed by Chevreuil (1839), illustrates how the appearance of a colour can change dramatically based on its surrounding colours, which has significant implications for design and visual perception.

Stained-Glass Illusion

  • This phenomenon further demonstrates how colour perception is intricately linked to surrounding hues, revealing the complex interplay between light and colour in visual arts.

Different Times, Different Lighting

  • Observations show that the same scene can appear differently under varying lighting conditions, emphasizing the concept of colour constancy while retaining the underlying truth of the colours.

Colour Constancy

  • This cognitive ability enables individuals to perceive stable colour in changing illumination conditions, indicating a complex interplay of sensory inputs and memory.

Colour Perception Experiment

  • Wallach (1948) conducted pivotal experiments illustrating how reference colours can significantly affect perceived brightness, contributing to our understanding of colour perception mechanisms.

Theories for Colour Constancy

  • Variations in perceived colour stability can be attributed to factors like cone excitation ratios, ongoing visual adaptation, and memory of past experiences relating to colour, emphasizing the cognitive aspect of colour perception.

Benefits of Colour Vision

  • Studies by Osorio and Vorobyev (1996) indicate that diverse types of colour vision confer unique advantages in object identification, influencing survival and interaction with the environment.

Importance of Colour Today

  • Research by Bramao et al. (2011) underscores the pivotal role of colour in object recognition and its use as a diagnostic tool in visual memory assessments, illustrating its relevance beyond aesthetics.

Colour and Emotion

  • Associations: Specific colours are often linked to evoking particular emotions, such as warmer colours representing joy, while cooler tones may communicate feelings of fear or sadness. This relationship is deeply rooted in cultural symbolism and psychological responses.

  • Research by Dael et al. (2016) highlights these associations, demonstrating how colour can affect human emotions significantly.

Colour Words and Emotional Associations

  • Findings by Jonauskaite et al. (2020) indicate that the verbal expression of colour can trigger emotional responses more powerfully than viewing colour patches alone, highlighting the complexity of human perception in interpreting colour.

Emotional Reactions to Colour

  • Valdez and Mehrabian (1994) found that bright and saturated colours are associated with positive emotional responses and heightened physiological arousal, underlining the psychological impact of colour choices on mood and behavior.

Colour Impact on Consumer Behaviour

  • Babin et al. (2003) explored how ambient colour can influence shopping behaviors, revealing significant differences between how cool and warm colours are perceived in retail environments, impacting customer engagement and sales.

  • Colour and Consumer behaviourBabin et al. (2003) examined the effect of cool (blue) vs. warm (orange)interiors on shopping behaviour.For a blue store: bright lights resulted inhigher price fairness perceptions.For the orange store: soft lights resulted in higher price fairness perceptions.

  • They also reported that when the lights are bright, a cool/blue setting is more effective than warm/orange setting in eliciting purchasing behaviour.

  • blue store + bright light - perception of fairnes for higher prices and more effective at eliciting purchasing behvauour

Colour and Appetite

  • Research by Wang (2020) suggests that red lighting can enhance appetite more effectively than cooler shades, useful information within the fields of food marketing and restaurant ambiance design.

  • the more saturated the colour, the my physiologically arousing this make the picture

Colour in Marketing

  • Pelet (2010) demonstrated that increased brightness and saturation in marketing materials can significantly boost purchase intentions and enhance consumer memory retention regarding products, thereby forming efficient marketing strategies.


Next Lecture

  • The upcoming focus will be on Spatial Vision, exploring its intricacies and contributions to the understanding of human visual perception.