Change Blindness. The greater the lie, the greater the chance that it will be believed.

Transcription

1 Change Blindness The greater the lie, the greater the chance that it will be believed. Department of Computer Science Rochester Institute of Technology 1

2 Definitions Seeing: the use of light to pick up information Sensing: unconsciously picking up information Scrutinizing: picking up information by focused attention Rapid Serial Visual Presentation: sequentially displaying text token by token (word/letter) Saccade: small rapid jerky eye movements Interstimulus interval: time between two or more stimuli 2

3 Forms of Induced Blindness Repetition Blindness: humans are less likely to detect a repetition in a RSVP stream Attentional Blink: failure to detect a 2nd target in RSVP if it occurs within ms after first target Inattentional Blindness: not being able to see things that are actually there Change Blindness: the inability to detect large changes in a scene that occur during a saccade or interruption 3

4 What causes the blindness? A complete representation of the world is never formed in memory Focused attention is necessary to see change Change is typically accompanied by a visual cue which draws our focused attention to it No visual cues with an interruption (ex: a saccade, film cut, image flash) 4

5 Motion vs. Change Motion instantaneous alteration of a quantity (location, color, etc) described in terms of derivatives (speed/acceler) Change change in the state of a quantity over a finite amount of time (temporal) not detected by low-level motion detectors possibly be accompanied by continuous motion 5

6 Experimental Setups One-shot: Image A, I.S.I., Image A ; change noticeable when I.S.I. < 80ms Flicker: Image A, Blank Screen, Image A ; changes take up to 50s to find! 6

7 Coherence Theory Focused Attention is necessary to see change Attention only lasts as long as your gaze Low-level processing forms proto-objects FA can grasp only a few proto-objects and request detail (=> objects) FA can be released and the objects collapse back into proto-objects Most of the image does not have a coherent representation (no FA => no change!) 7

8 Coherence Field 8

9 Inattentional Blindness Without attention, there is no visual experience of change (Coherence Theory) Unattended stimuli are seen, but not remembered Inattentional Blindness => Inattentional Amnesia Gorilla in the basketball video? Was it seen? 9

10 Seeing, Sensing, Scrutinizing Seeing The use of light to carry out various tasks How information is managed Sensing Scrutinizing 10

11 Virtual Representation Only represent the properties of specific objects that we need for a given task Reduces complexity requirements few objects need a coherent representation a coherent representation can be requested Lazy Loading Design Pattern defer initialization of an object until the point at which it is needed Like a computer system s RAM (load + swap!) 11

12 Triadic Architecture 12

13 Triadic Architecture Early Vision* high-capacity system, generates proto-objects Attentional Vision* low-capacity system, generates coherent objects Nonattentional Vision low-capacity system, guides focused attention (gist and spatial layout of a scene) * Explained in Coherence Theory 13

14 Task Based Vision Detection of change depends on the task Nature of the task affects when the item is attended properties of item attended (color, orientation) The only aspects placed into coherent form are those which serve the functional needs of the observer 14

15 Knowledge Based Vision Changes to objects that have been learned at a specific level are easier to detect than those learned at a general level Observers are quicker to spot changes if they can relate to the change (same social class) Experts are quicker to spot changes (they code scenes better than normal people) 15

16 Seeing, Sensing, Scrutinizing Seeing Sensing Processing of visual information without conscious awareness All aspects of vision that do not involve visual experience Includes visual awareness and implicit vision Scrutinizing 16

17 Visuomotor System Vision composed of 2 independent systems: online stream: immediate motor action offline stream: conscious perception/recognition Visuomotor system reacts before a conscious perception of change occurs When grasping a moving object, you correct the trajectory of your hand unconsciously (the targets may not be attended) 17

18 Implicit Perception Show a stimulus, mask it immediately, observer becomes primed, but unaware of stimulus (perception w/o attention!) Even if observers didn t see the change, they can guess (and do so better than chance) Explicit perception of change requires FA Implicit perception of change does not Perceived by a nonattentional stream of the triadic architecture 18

19 Mindsight 19

20 Mindsight Sensing the a change is occurring without a visual experience Know that a change is occurring Not know what exactly the change is Observers can have an abstract mental experience without sensory information Phenomenon is due to a nonattentional mechanism (like an alert) 20

21 Seeing, Sensing, Scrutinizing Seeing Sensing Scrutinizing Application of focused visual attention Applies to specific items or objects 21

22 Perception of Change 22

23 Perception of Change Speed reaction time increases linearly with the number of items (indicates constant search speed) Capacity # of items that can be grabbed until saturation Selectivity how fast are items of a certain class compared Task detection, identification, or localization 23

24 Change Results Presence: 100ms/item; 4-6 items at a time Find the item that is changing Absence: ms/item; 1.4 items Find the item that is not changing Conjunction: ms/item; 1 item Find the item varying 2 dimensions instead of 1 Presence is quickly detected, absence or conjunction is much slower 24

25 Attentional Mechanisms Info from attended items is aggregated capacity is higher for presence than absence search speed is ms formation of a coherence field is ms search is fast because CF isn t setup each time Number of attended items is <2 or <1 follows from capacity limits of 1.4 and 1 Little intrafield binding occurs 25

26 Visual Operations 26

27 Videos + Demos Movie_List.html 27

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