Lecture 1 – An Introduction to Vision: Defining the Problem

Question 1

What is the purpose of vision?

Answer 1

To detect visual stimuli so we can appropriately interpret and respond

Question 2

What is the problem when comparing vision to a camera?

Answer 2

Cameras/computers do not have the high level of performance that biological vision has - can’t detect things in a complex natural scene

Question 3

What do cameras pick up?

Answer 3

Cameras pick up the colour/light from a localised space in the environment (pixel)

Question 4

What is the purpose of perception?

Answer 4

produce meaningful and adaptive representations of the image and the environment

Question 5

Describe the Craik - O’ Brien - Cornsweet Effect and what cameras vs humans detect

Answer 5

This is where there are two blocks of the same colour but one has a lighter gradient. This means humans detect the box with the gradient as being lighter (we pick up on it to produce something more meaningful) but cameras do not have this perception so just see it for what the boxes are (the same colour).

Question 6

What is the inverse optics problem, and how is it solved (ish)?

Answer 6

This describes the problem of retrieving all info about a 3D environment from a 2D image (taking in info about depth, size etc). It is solved through humans using assumptions/prior knowledge to build images further (use of this shown when detecting two tones images after seeing the og one)

Question 7

Describe the information processing paradigm

Answer 7

Input (stimulus) –> Brain/Mind, information processing –> Output (Perception)

Question 8

Methods: Describe Psychophysics

Answer 8

determine the quantitative relationship between stimulus and perception by measuring thresholds

Question 9

In psychophysics, what is a way thresholds can be measured?

Answer 9

Alternative – Forced – Choice Paradigm

Question 10

(psychophysics) What are absolute thresholds?

Answer 10

the smallest amount of stimulation that can be reliably detected

Question 11

(psychophysics) Hard thresholds (absolute)

Answer 11

is a definitive perceptual difference in contrast levels

Question 12

(psychophysics) Soft thresholds (absolute)

Answer 12

perception/lack thereof is more gradual

Question 13

(psychophysics) Difference threshold

Answer 13

asked if which one had a higher contrast (just noticeable difference JDN)

Question 14

(psychophysics) Is the JND remain constant across stimuli intensities?

Answer 14

No - JND is based on the ratio/proportion between JND and reference intensity is constant (constant called Weber Fraction).

Question 15

Method: Electrophysiology

Answer 15

A microelectrode is located near/inside neurones to pick up on the action potentials (how neurones communicate - electrical activity). Provides info of individual/small numbers of neruones

Question 16

Methods: Neuroimaging techniques

Answer 16

Picking up consequences of electrical signals in the brain without needing to directly access it (EEG/MEG)

Question 17

Methods: Computational Methods

Answer 17

Build mathematical models of information processing at different levels which provides very precise explanations of biological vision (mechanistic and functional).

Question 18

Methods: Neuropsychology and Neuropsychiatry

Answer 18

studying individuals with brain lesions or neurological/psychiatric conditions.