Lecture 3- Object and face perception Flashcards
What is object perception?
We don’t see features we automatically put them together into meaningful parts and we see them as the whole object
What is object perception needed for?
Survival
What is detection and recognition?
We group objects together in different senses and then we use the memory to decide what it is
What is feature detection?
Part of the brain is selective for different features for example contrast boundaries
What are examples for features?
Colour, orientation and spatial frequency
What does low spatial frequency do in object recognition?
Convey rapidly to higher order brain areas by fast magnocellular pathways
What does high spatial frequency do in object recognition?
Convey slowly by parvocellular pathways
What is low level analysis?
Encoding features such as brightness, colour contrast, spatial detail, orientation and texture
What is high level analysis?
Understanding of the meaning
What does the presentation of visual stimuli lead to in feature processing?
Detailed processing of basic features to identify cortical cells involved in processing
Who studied cortical cells?
Hubel and Wiese
What did Hubel and Wiese do?
Studied the cells in the part of the occipital cortex in early stages of visual processing
What did Hubel and Wiesel find?
There are two types of neurones in the primary visual cortex: simple cell and complex cell
What does simple and complex cells do?
Provide ambiguous information and respond in the same way to different stimuli
We combine info from many neurones to remove ambiguities
What is grouping?
When the brain has automatic rules for deciding how to organise features to form an object
What are the three groupings found by Zanker?
Law of proximity, law of similarity and common fate
What is law of proximity?
Grouping of object close together
What is law of similarity?
Grouping of those similar
What is common fate?
Humans perceive visual elements that move in the same speed or direction
What is the most powerful cues from grouping?
Proximity when decide which contours belong to which objects
Who looked at grouping by uniform connectedness?
Palmer and Roch
What did Palmer and Roch find?
Grouping by uniform connectedness dominated proximity and similarity
What is contour for visual object?
Extracting objects for different spatial scales, neurones will respond at low and high spatial frequencies
What is Biederman recognition by components?
Turning 2D information into 3D information
What is the first stage in Biederman recognition by components?
Early edge extraction stage responsive to differences in surface characteristics
What is the next step in Biederman recognition by components?
Deciding how a visual object should be segmented to establish its components
What are of particular value in Biederman recognition by components?
The concave parts of an object’s contour
What are the 5 properties of edges in Biederman recognition by components?
Curvature, parallel, cotermination, symmetry and collinearity
What is Milner and Goodale’s two system model?
Object recognition and perception depend on the ventral visual stream
Is hierarchically organised
What happens to the stimuli causing the greatest neuronal activation in Milner and Goodale’s two system model?
Becomes progressively more complex as processing moves along the ventral stream
What are the certain conjunction of contours?
T-vertex, Y-vertex and arrow-vertex
What is view independent representation?
The ability to visual an object and see it from a different perspective such as rotation of the object
How do we recognise an object?
We have to have an idea of its 3D shape
What is the role of expectation?
Each person brings different experience and expectations and stimuli show that what we expect has influence on what we perceive
Why do we consider face perception separately?
Important as part of our communication with each other in an evolutionary process and is very constrained