COG PSYCH 3

• Unable to perceive motion

  • Seeing ‘nothing in between’ location changes

  • EX) Parked cars vs moving cars

What is Akinetopsia?

• Vision is the most dominant sense in humans

  • There is more brain area devoted to vision than the other senses

  • If visual inputs conflict with other sensory inputs, visual inputs generally dominate the final perception

    • EX) Puppet shows, we don’t see the puppet master but since we see the puppets instead, we generally focus on them instead of the puppet master.

Which is the most dominant sense in humans?

• Light comes into the cornea → lens → retina

  • The cornea and lens focus the light on the retina

How does light enter the eyes?

• Sensitive to low levels of light

• Lower acuity

  • Does not produce a higher resolution, rods produce lower quality images.

• Color-blind

• None in the fovea

• EX) Shining bright light into our eyes tells our rods that the ‘sun is up’, which is why people are told not to use your phone before sleeping.

What are Rods?

• Cannot function in dim light

• Higher acuity

• Color-sensitive

• Mostly in, or near, the fovea; none in the periphery

What are Cones?

• Rods and cones do not report directly to the cortex

  • Photoreceptors → Bipolar Cells → Ganglion Cells

  • Ganglion cells to the thalamus via the optic nerve

    • Lateral Geniculate Nucleus (LGN)

  • After the thalamus, it goes to the occipital lobe

What is the pathway for rods and cones?

• Lateral Inhibition is when cells are stimulated, they inhibit the activity of neighboring cells.

  • Results in edge enhancement

What is lateral inhibition?

The relationship between activity in the nervous system and the stimulus that is somehow represented by this activity

What is Coding?

• Single-cell coding in psychology and neuroscience links individual neuron electrical activity to specific mental processes like perception, memory, and language.

• Most knowledge of the visual system comes from single-cell recordings

  • Each cell in the visual cortex has a receptive field (what we can physically see)

    • There are specific cells that respond to different stimuli in what we physically can see

  • Neuron firing rate depends on the stimuli presented

What is Single Cell Coding?

In psychology, pattern coding and pattern recognition refer to how the brain sorts information, identifies regularities in data, and groups qualitative research codes into broader themes

What is Pattern Coding?

• Stimulus is presented in the center of the receptive field leads to faster firing rates

• Therefore, stimulus outside of the center leads to slower, below-baseline firing rates

• However, a stimulus covering the entire receptive field has the same effect as no stimulus

• The less similar a stimulus is to the cell’s ‘preferred’ stimulus, the less often the cell fires.

What are Center-Surrounded Cells (“dot detectors”)?

• Orientation (edge detectors)

• Angles

• Motions and Directions (movement detectors)

• Corners

What are other receptor specializations?

• When presented with different images of a hand, there are different neural activity with each image.

• Each image was of a hand, but at different qualities, when it decreased in quality, it seemed to have a weaker response.

What is an example of when we code specific targets?

The brain's ability to split a visual scene into multiple components—specifically color, motion, shape, and depth—and analyze them all at the same time

• No longer coding with a single neuron at a time, but now a loop between different cortexes

• Creates a more complex pattern than the previous ones

What is Parallel Processing in the Visual Syste,?

• Visual system is more faster and efficient

  • EX) Object recognition doesn’t need to wait for movement recognition in order to work.

• Has a mutual influence among multiple systems

  • Resolves contradictory demands

What are the Advantages of Parallel Processing?

However, as a weakness, it tends to be less accurate due to speed being a priority.

What is a weakness of Parallel Processing??

• Pathway connecting the occipital lobe and inferotemporal cortex

• Aids in identification of visual objects

  • EX) Recognizing a face, someone you already know

  • Damage leads to visual agnosia

What is the ‘What’ System?

• Pathway connecting the occipital lobe and the posterior parietal cortex

• Aids in the perception of an object’s location

  • Damage leads to difficulties reaching for objects

What is the ‘Where’ system?

• The task of reuniting elements of a stimulus that were addressed by different systems in different brain regions

  • EX) How are the ‘What’ and ‘Where’ systems coordinated?

What is the ‘Binding Problem’?

• 1. Spatial Position

  • An overlay map of ‘which forms are where’ with a map of ‘which colors are where’, ‘which motions are where,’ etc.

• 2. Neural Synchrony

  • Attributes are registered as belonging to the same object if the neurons detecting these attributes fire at the same time (in sync)

• 3. Attention

  • With insufficient attention, conjunction errors are common

  • EX) Less objects = more attention and less room for error. More objects = less attention (overloading) and more room for error.

What elements help with solving the binding problem?

• Perception of stimuli goes ‘beyond the information given’

  • Gestalt Psychologists: the perceptual whole is often different than the sum of its parts

  • Demonstrated by reversible (or ambiguous) figures

    • EX) The Necker Cube

What is Form Perception?

• Similarity – tend to group things based on a similar factor.

• Proximity - tend to group things based on how close they are with one another

• Good Continuation – tend to assume that things continue when blocked by something 

• Closure – when a figure is incomplete (i.e. a triangle) we can assume what the full figure is

• Simplicity – interpreting a form in the most simplest way possible.

What are the Gestalt Principles?

• Information gathering

• Interpretation

What activities are involved in perception?

• We perceive constant object properties (sizes, shapes, etc.) even though sensory information about these attributes change when viewing circumstances change

  • Brightness Constancy

    • Our visual ability to perceive objects as having a stable level of brightness, shape, and color

  • Size Constancy

    • Where your brain perceives an object as maintaining its actual physical size, regardless of its distance or the size of its image on your retina

  • Shape Constancy

    • Correct perception of an object’s shape changes in its shape on the retina

    • EX) A door opening, you assume that the door hasn’t changed despite it looking different.

What is Perceptual Constancy? What are some examples of it?

An involuntary, automatic mental process to explain how the brain builds complete, three-dimensional visual perceptions from incomplete sensory data.

What is Unconscious Inference?

• The role of interpretation in perception becomes clear from misinterpretations

• EX) Are these two figures the same size? Yes, but the convergence of lines leads to the initial perception that they are NOT the same size.

What are Illusions?

• How do people in different countries perceive the world?

  • Cultures differ in what they pay attention to

  • Eastern cultures have more emphasis on context than Western cultures

    • EX) West Asia (Middle-East) cultures don’t tend to focus on eye contact, but when we move more West, then eye contact is more focused

What are the Cultural Differences to visual perception?

We need to know the distance to be successful at size judgements and to interact successfully with the surrounding world

How do we perceive depth?

• Binocular Disparity

  • The difference between each eye’s view of a stimulus

  • EX) Put thumb out, close left eye and open right eye, and then close right eye and open left eye

• Monocular Cues

  • Depth cues that depend only on what each eyes sees by itself

    • EX) Lens adjustment

    • EX) Pictorial cues, including interposition

What are the different ways to percieve depth?

• There is some redundancy across different cues

• However, different cues become more or less important under different circumstances

  • EX) Binocular disparity is only informative when objects are relatively close to the viewer

What is the role of redundancy?