Perception and Action

119 Pre-attentive Vision

Learning Objectives

Know what we can perceive without attention and what we will miss when first directing our eyes.

Be able to describe what bottom-up salience and scene gist mean.

Know how subsequent saccades are directed by a combination of salience and top-down knowledge.

A scene gist is a brief scenery, sometimes without attention, that the brain processes to obtain the essence of what the scenery is about. It can let you determine with a short glance of the scenery whether what you are seeing is indoors/outdoors, an animal/person, a mountain/sea, and basic geometries. Without attention, we can perceive the scene gist of our surroundings, but not any details that may be perceived upon closer attention.

Bottom-up salience is defined as the degree of difference between a stimulus and its neighbors. Many objects are observed along with its neighboring objects. The brain observes the target object’s orientation and separates the object from the neighboring objects with differing orientations.

 

12.2.1. Bottom-Up Salience. While looking at this image, your brain separates the blocks as individual elements based on their relative orientations. (Credit Jarod Davis. Provided by: University of Minnesota. Based off William Daigneault Original image. License: CC-BY 4.0)

The subsequent saccades are directed by a combination of salience and top-down knowledge. The salience influences saccades more from individual features of objects and contrasting luminescence, intensity, etc. The top-down knowledge influences saccades depending on what your goals are for looking at the scene (a person, building, etc).

 

Exercises

  1. Which two phrases fill in the blanks most properly? While looking at a scene with bottom-up salience, the brain focuses more on ___________, whereas with top-down knowledge, the brain focuses more on ________.
    A. gathering all the information; the colors and shapes in the scene
    B. individual features; the surrounding context
    C. what you are expecting to see; what you are not expecting to see
    D. the bottom of what you are seeing; the top of what you are seeing

Answer: B

 

CC LICENSED CONTENT, SHARED PREVIOUSLY
Cheryl Olman PSY 3031 Detailed Outline
Provided by: University of Minnesota
Download for free at http://vision.psych.umn.edu/users/caolman/courses/PSY3031/
License of original source: CC Attribution 4.0

 

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Introduction to Sensation and Perception by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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