L1 - Intro to vision: defining the problem Flashcards
1
Q
Is vision simple?
A
- Similar to a camera
- Straightforward
- BUT when college students were asked to recreate this with AI, there was no model that matched to the biological vision.
2
Q
What is deep learning?
A
- Modern machine vision
- Very powerful but easy to fool
- Work in very different ways to how the human works
3
Q
How is vision deceptively simple?
A
- e.g Computer won against the best chess player of the time
- Computers are nowhere nearly as good as humans in detecting vision
- Vision = complex
- Visual brain = large proportion is dedicated to processing visual info
4
Q
How do camera record?
A
- Light enters from object onto lens which is reflected onto the sensors
- Only when the red light is persistent, even if not relevant
- Records light intensity
5
Q
The visual system is not a camera?
A
- Purpose of camera is to record local light intensities
- Purpose of perception is to generate meaningful and adaptive representations, especially if there are explicit aspects of the environment
- Meaningful and adaptive representations encode specific aspects of the world to help guide behaviour.
6
Q
What is the Craik O’Brien Corn street Effect?
A
- Same colour in different places
- But makes you feel like two diff colours depending on what surrounds it
7
Q
What are optics and inverse optics?
A
- Through the eyes, an object is projected onto the retina = form an image (optics)
- Visual system tries to infer which object is out there from the image on the retina
- Often using this process for vision is ambiguous so we use prior knowledge or assumptions to help
8
Q
What is the information processing paradigm?
A
- Input (stimulus) –> brain/mind - info processing –> Output (perception)
9
Q
How is vision science transdisciplinary?
A
- Derived concepts from psych, neuro
- Level of analysis = from neurons to percepts
10
Q
What is Psychophysics?
A
- Tries to determine the relationship between stimulus and perception quantitively
- Psychophysicists measure thresholds and limits of the perceptual system
- Studies perception at the level of the whole organism
11
Q
What are the types of measures for threshold?
A
- Absolute: smallest amount of stimulation that can be reliability detected
- Difference: smallest difference between two stimuli that can be reliably detected
12
Q
How to measure absolute threshold (contrast)?
A
- 2-alternative-forced-choice task
- Show ppts 2 different stimuli, one containing stimulus (stripey patterns) and one is grey and plain
- Reduce the contrast of the stripey pattern where ppt is JUST able to see the difference between blocks
- RESULTS: there is no hard threshold for a certain amount of stimulus to be seen BUT there is a soft threshold, some ppt will never be able to see it so will guess, and others will see it always, some trials they will see and others they will not
- ABSOLUTE: what level will they identify at e.g when are they 75% sure, stimulus intensity for a ppt to recognise it
13
Q
How to measure difference threshold?
A
- Use the 2-alternative-forced-choice task
- Both have a stripey pattern, one is the reference/standard and you have a comparison
- Ref = fixed stim intensity
- Ask which one has a higher contrast
- Change the contrast until ppt is just able to see the difference between the two
- Also known as the just noticeable difference
14
Q
What is the Weber Fraction?
A
- Checking if the just noticeable difference a constant stimulus intensity?
- Checked via an experiment holding weight, if you find a JND, then change the reference, will the JND stay the same?
- The ratio between JND and reference intensity is constant
15
Q
What is electrophysiology?
A
- Neurones communicate via action potentials
- Microelectrode located near & neuron is able to pick up this activity
- Provides info about processing in individual neurones or a small number of neurons
