Extramission Theories
- Includes Euclid and Plato
- Theory: A stream of light or fire comes from the eyes to allow us to see objects
Intromission Theories
- Democritus; Objects cast off some kind of material substance that enters the eye
- Epicurus; Objects cast off one-atom-thick layers that arrive in the eyes
- Made sense of object constancy
Aristotle’s Theory of Visual Perception
- Rejected extramission theory
- HIs and his pupil’s theory: Light was generated from the Sun and reflected from objects. It travelled through a medium (air) to the eye. Without this medium, we would see nothing.
Alhazen’s Contribution to Visual Perception
- Considered the ‘father of modern optics’
- Studied stereopsis, refraction and several illustrations including moon illusion
- Proposed that rays originate from objects, not eyes
- Proposed that vision occurs in the brain, not the eyes
- Proposed that experience affects perception, and hence perception can be mistaken
17th Century Physics: Johannes Kepler
“… Thus vision is brought about by a picture of a thing seen being formed on the concave surface of the retina” which basically means that an image is formed/starts in the retinal surface of the eye
17th Century Physics: Isaac Newton
Many contributions but the one highlighted in the topic of visual perception is his use of prisms to decompose white light into its spectral components.
18th Century Philosophy: If starting point is 2D retinal image, how do we see a 3D world?
- Locke and Berkely; Rejects the empiricist position that all knowledge is innate
- Immanuel Kant; Rejects the empiricist position that all knowledge is learned and suggests that there must be some inborn assumptions or categories
- A nature vs nuture debate
Definition of Psychophysics
Systematic study of the relationship between sensations and physical events
19th Century Psychophysics: Gustave Fechner
- Influential scientist in Leipzig
- Introduced the term, “psychophysics”
- Published the ‘Elements of Psychophysics’ in 1860
- Fechner et al. introduced methods still used today, e.g. Method of limits, Method of constant stimuli
19th Century Psychophysics: Ernst H Weber
- Influential scientist in Leipzig
- Noticed that JND in some sensory dimension or other is a constant proportion of usually about 3%
- Weber fraction -> (I₂ - I₁)/I₁ = constant
Biography of Hermann von Helmholtz
- Studied medicine
- Published ‘Handbook of Physiological Optics Vol. 1’ (1856)
- Chair of Physiology at Heidelberg (1858)
- Chair of Physics at Berlin (1871)
- His biography is an example of how ideating the basis of psychology required mastery across different disciplines
Hermann von Helmholtz’s Contributions
- Invented ophthalmoscope (allows you to look into the back of the eye to look at the health of the retina, optic nerves, etc.)
- Associationist and empiricist doctrine
- Unconscious inference (what people use to deduce what they perceive)
- Theory of depth perception (visual cues plus felt positions in space, learned by associations)
- Young-Helmholtz trichromatic theory of colour perception
Hermann von Helmholtz’s Contributions
- Invented ophthalmoscope (allows you to look into the back of the eye to look at the health of the retina, optic nerves, etc.)
- Associationist and empiricist doctrine
- Unconscious inference (what people use to deduce what they perceive)
- Theory of depth perception (visual cues plus felt positions in space, learned by associations)
- Young-Helmholtz trichromatic theory of colour perception
Associationist Theory
The theory that complex mental processes (ex. thinking, learning, and memory) can be wholly/mainly explained by the associative links formed between simpler ideas
Associationist Theory
The theory that complex mental processes (ex. thinking, learning, and memory) can be wholly/mainly explained by the associative links formed between simpler ideas
The Birth of Experimental Psychology: Wilhelm Maximilian Wundt
- Previously studied with Muller and worked at Heidelberg with Helmholtz
- The “first” psychological laboratory in University of Leipzig (1879)
- Clearly distinguished ‘experimental’ psychology from ‘social’ psychology (through his attempts to control the settings/environment)
- Proposed psychology as the science of consciousness; Aimed to show how elements of consciousness are combined to form perceptions and ideas, through introspection
Importance of Germany and Leipzig
- Many of Psychology’s early leaders and Gestalt psychologists all worked in Germany
- This early leadership in Psychology was disrupted by the world wars and division of Germany
- Leipzig is the second-oldest university in Germany and the first in the world to hold a psychological laboratory
- Leipzig University was renamed ‘Karl Marx University’ under the Soviet regime
- After reunification of East and West Germany, Leipzig University again flourishes
- Leipzig today houses two Max Planck Institutes (MPI or Evolutionary Anthropology and MPI of Cognitive Brain Sciences)
20th Century Vision: The Three Primary ‘Schools’
- Gestalt Psychology
- JJ Gibson’s ecological optics
- Richard Gregory’s constructivism
Edward B. Titchener
- PhD with Wundt
- After, he went to America and established a lab at Cornell in 1892 to pursue ‘Structuralism’
- Used introspection (to determine different components of consciousness)
- His approach was challenged by Gestalt psychologists
Important Figures in Gestalt Psychology
- Max Wertheimer
- Kurt Koffa
- Wolfgang Kohler
- All three educated and practiced in Germany during WW1 but moved to the US before WW2
What is Gestalt Psychology’s theory?
- A school of thought that suggests the human mind looks at the world as a whole, instead of focusing on every small component.
- Gestalt theory emphasizes that the whole of anything is greater than its parts.
Titchener’s Structuralism
- Introspective analysis of the basic elements of conscious experience
- Seeks to analyze the elements of mental experiences (ex. sensations, mental images, and feelings) and how these elements combine to form more complex experiences
Examples of the Gestalt Laws of Perceptual Organisation
- Proximity: Things that are close together are grouped together
- Similarity: Things that look similar are grouped together
- Common Fate: Things that move together are grouped together
- Good continuation
Behaviourism and its Influence (Visual Perception)
- Emerged in America at roughly the same time as the Gestalt period in Germany
- Stimulus implies an impoverished input (unlike JJ Gibson)
- Minimised cognitive activities that intervene between ‘stimulus’ and ‘response’ (unlike Richard Gregory)
