CORNELL UNIVERSITY CS 764 Seminar in Computer Vision Attention in visual tasks

CORNELL UNIVERSITY 2 Two different tasks n Perception of motion Experiments indicate systems similar to the ones used in computer vision n Object representations and visual memory Results indicate systems different from anything we implement

CORNELL UNIVERSITY 3 Attention and motion n Todd Horowitz and Anne Treisman Spatial Vision Vol. 8, No. 2, 1994 n Apparent x Real motion n Short range x Long range system

CORNELL UNIVERSITY 4 Short range x Long range system n Short range Small displacement Small time interval between stimuli Constant contrast n Long range Everything else

CORNELL UNIVERSITY 5 Theoretical framework n Short range motion Array of simple motion detectors operating in parallel. (like optical flow computation) n Long range motion Depends on linking stimuli separated in space and time. Requires attention (like shape matching)

CORNELL UNIVERSITY 6 Experiment 1 n Detection of long and short range motion with unicontrast and bicontrast stimuli n Measure response time as a function of number of distractors. Parallel search => constant time Serial search => linear time

CORNELL UNIVERSITY 7 Experiment 2 - Motion Aftereffect n The effects of adaptation are reversed between short and long range motion. n Short range system becomes less sensitive to adapted motion n Long range system benefits from ‘practice’ stimuli

CORNELL UNIVERSITY 8 Summary n Two different systems for motion perception We have decent models for both systems n Short range motion seems much like optical flow computation n Long range motion seems much like shape matching

CORNELL UNIVERSITY 9 Object Tokens, Attention, and Visual Memory n Anne Treisman and Brett DeSchepper Attention and Performance XVI, 1996 n Probe bottom-up registration of unattended objects n Specially novel objects, for which new representations may be constructed

CORNELL UNIVERSITY 10 Introduction n On recognition tasks, we can’t remember novel unattended shapes n But indirect measures (i.e. priming) reveal memory beyond conscious level n How much processing and learning happens without attention?

CORNELL UNIVERSITY 11 Experiment 1 n Tests indicate unattended shapes cause negative priming Few subjects show facilitation n Very long duration of effect (> weeks) n No explicit memory of unattended shapes

CORNELL UNIVERSITY 12 Experiment 2 n Are there differences between representations built for attended and unattended shapes? n Maybe attended shapes are processed to a higher level and representations reflect this

CORNELL UNIVERSITY 13 Summary n No explicit memory of unattended novel shapes n Priming indicates implicit memory n Implicit memory “learns” with one example and repetition is irrelevant. n Effects last for long periods (novel shapes) n When attended, novel shapes are processed to a higher level.