Stimuli in receptive field of neuron

1. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

2. Stimuli in receptive field of neuron Computer Vision Lecture 2: Vision, Attention, and Eye Movements

3. Cat V1 (striate cortex) Orientation preference map Ocular dominance map Computer Vision Lecture 2: Vision, Attention, and Eye Movements

4. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

5. Structure of NNs (and some ANNs) • In biological systems, neurons of similar functionality are usually organized in separate areas (or layers). • Often, there is a hierarchy of interconnected layers with the lowest layer receiving sensory input and neurons in higher layers computing more complex functions. • For example, neurons in macaque visual cortex have been identified that are activated only when there is a face (monkey, human, or drawing) in the macaque’s visual field. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

6. “Data Flow Diagram” of Visual Areas in Macaque Brain Blue:motion perception pathway Green:object recognition pathway Computer Vision Lecture 2: Vision, Attention, and Eye Movements

7. Receptive Fields in Hierarchical Neural Networks neuron A receptive field of A Computer Vision Lecture 2: Vision, Attention, and Eye Movements

8. Receptive Fields in Hierarchical Neural Networks receptive field of A in input layer neuron A in top layer Computer Vision Lecture 2: Vision, Attention, and Eye Movements

9. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

10. Face aftereffect – Thanks to ArashAfraz for the slides! Computer Vision Lecture 2: Vision, Attention, and Eye Movements

11. Visual Illusions Visual Illusions demonstrate how we perceive an “interpreted version” of the incoming light pattern rather that the exact pattern itself. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

12. Visual Illusions He we see that the squares A and B from the previous image actually have the same luminance (but in their visual context are interpreted differently). Computer Vision Lecture 2: Vision, Attention, and Eye Movements

13. Visual Attention • Visual attention is the selective allocation of visual processing resources. • For example, we can focus our attention on a particular object of interest in the visual field. • Visual processing of that object is enhanced while being rather shallow for other objects. • Also, we can respond more quickly and accurately to changes in an attended region. • This prioritization is necessary due to our limited processing resources. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

14. Visual Attention • The attentional cueing task introduced by Michael Posner gives insight into the dynamics of visual attention. • Subjects are instructed to fixate on the central cross. • One of two boxes (left or right) flashes to capture the subject’s attention (an automatic, involuntary response). • After some a short delay (stimulus onset asynchrony - SOA) an asterisk appears in one of the boxes. • The subject has to report as quickly as possible in which box the asterisk appeared. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

15. The Posner Attention Task x Computer Vision Lecture 2: Vision, Attention, and Eye Movements

16. The Posner Attention Task x Computer Vision Lecture 2: Vision, Attention, and Eye Movements

17. The Posner Attention Task x Computer Vision Lecture 2: Vision, Attention, and Eye Movements

18. The Posner Attention Task • * x Computer Vision Lecture 2: Vision, Attention, and Eye Movements

19. The Posner Attention Task x Computer Vision Lecture 2: Vision, Attention, and Eye Movements

20. The Posner Attention Task • For short SOAs (< 200 ms), subjects respond faster if flash and asterisk appear on the same side. • Cueing of attention to relevant location allows faster response. • For longer SOAs, subjects respond more slowly if flash and asterisk appear on the same side. • Inhibition-of-Return mechanism makes attention less likely to remain on the side of the flash until the asterisk appears. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

21. Eye Muscles Eye Movements Computer Vision Lecture 2: Vision, Attention, and Eye Movements

22. Types of Eye Movement Fixations: • The eye is almost motionless, for example, while reading a single, short word. • The information from the scene is almost entirely acquired during fixation. • Duration varies from 100-1000 ms, typically between 200-600 ms. • Typical fixation frequency is about 3 Hz. • Fixations are interspersed with saccades. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

23. Types of Eye Movement Saccades: • Quick “jumps” that connect fixations • Duration is typically between 30 and 120 ms • Very fast (up to 700 degrees/second) • Saccades are ballistic, i.e., the target of a saccade cannot be changed during the movement. • Vision is suppressed during saccades to allow stable perception of surroundings. • Saccades are used to move the fovea to the next object/region of interest. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

24. Types of Eye Movement Smooth Pursuit Eye Movements: • Smooth movement of the eyes for visually tracking a moving object • Cannot be performed in static scenes (fixation/saccade behavior instead) Computer Vision Lecture 2: Vision, Attention, and Eye Movements

25. Why Eye-Movement Research? About eye movements and visual attention: • Usually, saccades follow shifts of attention to provide high acuity at the attended position. • It is possible to look at an object without paying attention to it (staring). • It is possible to shift attention without eye movement (covert shifts of attention). • It is impossible to perform a saccade while not shifting attention. • During specific, natural tasks it is reasonable to assume that saccades follow shifts of attention. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

26. Why Eye-Movement Research? The investigation of visual attention, in turn, is at the core of cognitive science. • Studying visual attention yields insight into general attentional mechanisms. • It can provide information on a person’s stream of conscious and unconscious processing while solving a task. • Attention is closely linked to the concept of consciousness. • Attentional mechanisms could improve artificial vision systems. Computer Vision Lecture 2: Vision, Attention, and Eye Movements

27. Eye-Movement Studies Eye movements while watching a girl’s face (early study by Yarbus, 1967) Computer Vision Lecture 2: Vision, Attention, and Eye Movements

28. Eye-Movement Studies Eye movements as indicators of cognitive processes (Yarbus): • trace 1: examine at will • trace 2: estimate wealth • trace 3: estimate ages • trace 4: guess previous activity • trace 5: remember clothing • trace 6: remember position • trace 7: time since last visit Computer Vision Lecture 2: Vision, Attention, and Eye Movements

29. Eye-Movement Studies Visual scan paths on instruments/dashboards – studies for the improvement of human-computer interfaces Computer Vision Lecture 2: Vision, Attention, and Eye Movements

30. Eye-Movement Studies Gaze trajectory measurement for the optimization of web page layout Computer Vision Lecture 2: Vision, Attention, and Eye Movements

31. Eye-Movement Studies Improving advertisements with eye-movement studies Computer Vision Lecture 2: Vision, Attention, and Eye Movements

32. Selectivity in Complex Scenes Computer Vision Lecture 2: Vision, Attention, and Eye Movements

33. Face Recognition Gaze-contingent window deteriorates face recognition, allows to identify relevant visual information. Computer Vision Lecture 2: Vision, Attention, and Eye Movements