PSY 1207 Cognition, Emotion & Development - Lecture II: Perception

This lecture introduces concepts, investigation methods, specific findings, and theories in the study of cognitive skills in human adults.
It explores methods used and the theoretical accounts pursued in cognitive studies.

Cognitive Psychology: Understanding human cognition through behavioral evidence.
- Behavioral data is crucial in cognitive neuroscience and neuropsychology.
- Cognitive psychology has a significant influence due to its reliance on observable behaviors.
Cognitive Neuropsychology: Studying brain-damaged patients to understand normal human cognition.
- Originally linked to cognitive psychology but now also connected to cognitive neuroscience.
- Inferences about cognitive functions are drawn from observing deficits caused by brain damage.
Cognitive Neuroscience: Using evidence from behavior and the brain to understand human cognition.
- Combines behavioral studies with brain imaging techniques (fMRI, EEG) to reveal neural correlates of cognition.
Computational Cognitive Science: Developing computational models to further our understanding of human cognition.
- Models increasingly consider behavior and brain data.

We know the world through our senses.
The core question: How does the energy of the outside world become a representation in the inside world?
We assume what we see, hear, smell, and taste is all there is, but how accurate are our senses in reflecting the outside world?

Humans perceive only a limited range of the electromagnetic spectrum (visible light).
The spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
Wavelengths range from long (kilometers) to short (picometers).

Humans perceive frequencies between 20 Hz and 20,000 Hz.
Other mammals perceive different ranges (e.g., elephants perceive infrasound, bats perceive ultrasound).
Sound intensity is measured in decibels (dB).
Exposure to sounds above 90 dB can cause irreversible damage.

Energy from the outside world is transformed into neural signals (firing of neurons).
Raw signals are picked up.
The brain recognizes what the signal means (e.g., seeing a ball instead of a round blob).
How a person perceives the world depends on how the world is represented in their brain.
Phantom limb phenomenon illustrates that perception is rooted in the brain.

Light enters through the pupil and is focused by the cornea and lens onto the retina.
Photoreceptors (rods and cones) in the retina convert light into electrical signals.
Signals are sent via the optic nerve to the lateral geniculate nucleus (LGN) in the thalamus.
From the LGN, information travels to the primary visual cortex (V1) in the occipital lobe.
Further processing occurs in other visual areas (V2, V3, V4, MT/V5, etc.) in the occipital and temporal lobes.

Bottom-up processing: Driven by sensory input (sight, hearing, touch, smell, taste).
Top-down processing: Influenced by knowledge, expectations, culture, experience, and memories.
The best possible interpretation of a stimulus results from the interaction of both.

Speech segmentation: Speakers of a language can distinguish individual words in a continuous sound stream due to their knowledge of the language.
Pain perception: Placebo effects demonstrate how expectations can reduce pain by refocusing attention.
Visual perception: Context and memory influence how we interpret visual stimuli.
- For example, the same symbol can be interpreted as a letter or a number depending on the surrounding context.

A particular pattern of activation on the retina can be caused by a range of objects.
Likelihood principle: We perceive the object that is most likely to have caused that pattern.
This judgment results from unconscious assumptions (inferences) about the environment, happening automatically.
We see objects in a 3-dimensional world.
If there is a chance to interpret an object as 3-dimensional, we do so.
Illusions show that we don’t see 2-dimensional rectangles as they are (equal size). Instead, we see the 3-dimensional shape of the objects in space.

Law of Similarity: Similar elements are grouped together.
Law of Pragnanz: We perceive the simplest, most stable shape.
Law of Proximity: Elements that are close together are grouped together.
Law of Continuity: We perceive continuous, smooth patterns rather than discontinuous ones.
Law of Closure: We tend to see complete figures even when part of the information is missing.
Law of Common Fate: Elements moving in the same direction at the same speed are grouped together.

Using these laws, the brain groups elements in the environment into entities or objects.
The next step is to figure out what that object is and what characteristics define it as a member of a category.

Distant items appear more blue due to the scattering of blue light in the atmosphere.
On clear days, mountains seem closer.
Scattering of light creates a blur; blurry things seem further away, while items with sharper contrast seem closer.