Spatial vision

Question 1

what is spatial vision?

Answer 1

• Spatial vision refers to the ability to perceive and interpret spatial relationships in our environment, including the location, size, and orientation of objects.
• It is crucial for navigating the world, recognizing objects, and performing everyday tasks such as reading and driving.

Question 2

what is spatial frequency?

Answer 2

• The level of detail present in a visual stimulus, measured in cycles per degree of visual angle.
• High spatial frequency for fine details (e.g., reading small text)
• Low spatial frequency for broad shapes (e.g., landscape).

Question 3

what is contrast sensitivity?

Answer 3

• The ability to detect differences in luminance between areas of lightness and darkness.
• In this case, how well can you discriminate the lighter sections from the darker sections.
• Contrast sensitivity is essential for us to be able to detect objects, in particular edges.

Question 4

how do we measure contrast sensitivity?

Answer 4

• One way to measure contrast sensitivity is to present patches with different levels of contrast and see how much you can reduce the contrast before the lines disappear.
• Different people will have different thresholds for the same patch.
• Your threshold is low, if you can just see the lines at a low contrast level. This means you have high sensitivity.
• Different people will have different thresholds for the same patch.
• Your threshold is high, if you can just see the lines at a high contrast level. This means you have low sensitivity.

Question 5

what is the contrast sensitivity of different animals?

Answer 5

• Campbell et al. (1973) measured the CSF for cats, and Potier et al. (2018) compared the CSF for human, cat and various birds of prey.
• While cats are more sensitive to lower spatial frequency (useful for the detection of motion), some raptors are sensitive to higher spatial frequencies.

Question 6

what is the fourrier analysis?

Answer 6

• When processing the images you see, the visual system relies on different channels.
• Each channel is specialized for different spatial frequencies at different orientations.

Question 7

what is the oblique effect?

Answer 7

• Campbell et al (1966)
• showed that we are differently sensitive to different orientations.
• We are most sensitive to horizontal and vertical orientations and much less so to diagonal orientations.

Question 8

what is the different level of vision?

Answer 8

• Foveal/central: 1-5 degrees
• Parafoveal: up to 8 degrees
• Peripheral: beyond 8 degrees
• The angle between where you are looking at and areas in your periphery is measured in degrees and is referred to as eccentricity.

Question 9

what is central vision?

Answer 9

• High Acuity: It provides the highest visual resolution, allowing us to see fine details, which is essential for tasks like reading, recognizing faces, and discerning colour.
• Colour Perception: It is rich in cone cells, making it sensitive to colour and enabling colour discrimination.
• Focused Attention: It is where we direct our gaze for tasks requiring precise focus, as this area provides the sharpest, most detailed view.

Question 10

what is parafoveal vision?

Answer 10

• Supporting Reading and Scanning:
  
  • It helps in processing information slightly off-center, which aids in activities like reading by providing a preview of nearby words. This allows us to move our eyes more efficiently across lines of text.
• Peripheral Preview for Focus Shift:
  
  • It also gives hints about what is in the near periphery, enabling quick, accurate shifts in focus, such as when we are scanning a room.

Question 11

what is peripheral vision?

Answer 11

• Detecting Motion:
  - It is highly sensitive to motion, which helps us detect movement in the environment. This is an evolutionary advantage for detecting threats or changes in our surroundings.
  Spatial Awareness:
  
  • It contributes to spatial orientation by via optic flow, allowing us to navigate our environment and maintain balance.
    Low Light Sensitivity:
  • It relies more on rod photoreceptors, which are better suited for low-light conditions, giving us greater night vision and awareness in dim environments.

Question 12

what are the factors that affect crowding?

Answer 12

• To et al. (2010)
• investigated how well participants can see difference in images when they are presented alone (A), amongst identical flakers at close distance (B), amongst repetitions of a different flanker at mid distance (C), and amongst several different flankers at far distance (D).
• Flankers made no difference in central vision but led to significant crowding in the periphery.
• The most effective flankers were those similar to the targets.
• Crowding effects were strongest when the target-flanker distances were short.

Question 13

how does crowding impact the development of dyslexia?

Answer 13

• Studies have reported that individuals with developmental dyslexia can experience less crowding in the periphery, but more in central vision, compared to controls (Geiger & Lettvin, 1987; Lorusso et al. 2004).
• Bertoni et al. (2019) found that the reading accuracy of children with dyslexia is improved with extra-large spaced text.
• Crowding-like mechanisms could also play a key role in numerical perception through ensemble coding when there are many objects.
• Castaldi et al (2020) showed that participants with developmental dyscalculia (DD) experienced more crowding compared to controls.

Question 14

what is purpose of peripheral vision?

Answer 14

• Peripheral vision is useful detecting sudden changes and movements and triggering foveation towards, or avoidance of, stimuli entering the field.
• The periphery is also essential in maintaining balance, both when we are stationary and when are moving (Brandt et al., 1973).