Perceptual Heuristics & Gestalt Principles of Perception Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/07/2015: Lecture 02-2 This Powerpoint presentation may contain macros that were used to create the slides. The macros aren’t needed to view the slides. If necessary, you can disable the macros without any change to the presentation.

The Cognitive Side of Perception Unconscious inference is pervasive in perception Bottom Up & Top Down Processing Inverse Projection Problem Perceptual heuristics Gestalt Principles of Perception: Some examples Preliminary topic to object perception Bottom Up & Top Down Processing Psych 355, Miyamoto, Spr '15

Bottom Up and Top Down Processing Bottom up processing – processing of current stimulation influences what is perceived Top down processing – person’s background knowledge, learning and expectations influence what is perceived. Bottom up processing is data driven. Top down processing is theory-driven, knowledge-driven, and context-driven. Example of top down processing: Your knowledge of rectilinear solids informs your perception. Examples of Top Down and Bottom Up Processing Psych 355, Miyamoto, Spr '15

Examples of Bottom Up Processes Elementary feature detection, e.g., edge detectors, bar detectors, motion detectors. The following color perception is bottom up:  Your perception of the red squares is dictated by the stimulus; the perception is not influenced by prior expectations or beliefs. Similarly, the perceived motion of the blue disk is bottom up. It is controlled by the stimulus, not by your beliefs or expectations. Example of Top Down Processing Psych 355, Miyamoto, Spr '15

Examples of Top Down Processes When people see a plane crash, at least some witnesses always claim to have seen flames coming from the engines. (Top-down when claim is false; either top-down or bottom up when it is true.) Scene understanding involves both top-down and bottom-up processing. Classroom Experiment Psych 355, Miyamoto, Spr '15

Class Experiment: Demonstration of Top Down Processing Instructor: Divide the classroom into a “left group” and “right group”. I will show you an image. Briefly write down a label for what you see. E.g., if you see a chair, write down “chair.” Left half of the room will close their eyes for the first image. Right half of the room will close their eyes for the second image. Everyone will open their eyes and complete the experiment. Image 1a Psych 355, Miyamoto, Spr '15

Students on Left – Eyes Open Students on Right – Eyes Closed Label this image “Image 1a”. Write down a name for what you see. Image 1b Psych 355, Miyamoto, Spr '15

Students on Left – Eyes Closed Students on Right – Eyes Open Label this image “Image 1b”. Write down a name for what you see. Image 2 Psych 355, Miyamoto, Spr '15

Label this image “Image 2”. Write down a name for what you see. Everybody’s Eyes Open Label this image “Image 2”. Write down a name for what you see. Collect Results of Class Demo Experiment Psych 355, Miyamoto, Spr '15

Results of Classroom Experiment We will only collect data for what you saw in Image 2. People on the LEFT SIDE: Raise your right arm if you wrote down “mouse” or “rat” for Image 2? Raise your left arm if you wrote down “old man” or “man” or “face” for Image 2? People on the RIGHT SIDE: Show Images 1a, 1b, 2 Psych 355, Miyamoto, Spr '15

. LEFT SIDE saw Image 1a RIGHT SIDE saw Image 1b Top Down Processing: What you see in Image 2 depends in part on what you expect from Image 1. EVERYONE saw Image 2 . Summary re Bottom Up & Top Down Processing Psych 355, Miyamoto, Spr '15

Summary re Bottom Up & Top Down Processing What we see is usually the consequence of both top-down and bottom-up processing. Remember Helmholtz’s unconscious inference. Top down processes (inferences) fill in information that is not present in the actual stimulus. Inverse Projection Problem Psych 355, Miyamoto, Spr '15

Inverse Projection Problem Object could be created by the larger more distant rectangle or the tilted trapezoid. Inverse Project Problem: For any 2-dimensional image that is projected onto the retina, there are infinitely many different 3-dimensional shapes that could have produced that image. How does the mind decide which shape actually produced the 2-dimensional projected image? 13 Ambiguous Figures: The Ambiguous Box Psych 355, Miyamoto, Spr '15

Example: Ambiguous Images Do you experience competing interpretations of the image? (I.e., do you experience "Gestalt shifts in perception") Box viewed from above, versus Box viewed from below 14 Young/Old Woman Psych 355, Miyamoto, Spr '15

Example: Ambiguous Images Do you experience competing interpretations of the image? (a.k.a. "Gestalt shifts in perception") Young woman versus Old woman mouth mouth 15 Same Image Without the “Mouth” Labels Psych 355, Miyamoto, Spr '15

Example: Ambiguous Images Do you experience competing interpretations of the image? (a.k.a. "Gestalt shifts in perception") Young woman, versus Old woman 16 Inverse Problem – How Does the Visual System Decide What is 3-D Object? Psych 355, Miyamoto, Spr '15

How Does the Visual System Answer the Question: What Is the Real Object That Produces the Stimulation at the Retina? Basic answers: The visual system makes a variety of unconscious inferences (Helmoltz's idea). The visual system uses cues for object relations that usually work (but the system can be fooled by a clever stimulus). What Is a Heuristic? Psych 355, Miyamoto, Spr '15

What is a Heuristic? A heuristic is a reasoning strategy that is used to solve a problem, make a decision or form a judgment about something. Perceptual heuristic: A strategy in perceptual information processing that (typically) helps to determine the objective situation that produced the immediate sensations. Heuristics are typically useful shortcuts. Heuristics are often adaptive, but they can lead to systematic errors. Craters versus Mounds Psych 355, Miyamoto, Spr '15

Example: Craters or Mounds? Typically Craters Typically Mounds “Light comes from above” assumption guides perception. Repeat this Slide with Ellipses that Pick Out Corresponding Craters and Bumps Psych 355, Miyamoto, Spr '15

Example: Craters or Mounds? Typically Craters Typically Mounds “Light comes from above” assumption guides perception. Why Idea of Unconscious Inference Is Important for Cog Psych Psych 355, Miyamoto, Spr '15

2-D Artwork That Looks Like 3-D (Sketch) Downloaded from: http://www.dailydot.com/entertainment/lego-chalk-army/ Work is attributed to: http://www.planetstreetpainting.com/ * See ‘E:\p355\IMAGES\2d.like.3d.ini.planetstreetpainting.jpg’ for the image. Psych 355, Miyamoto, Spr '15

2-D Artwork That Looks Like 3-D (Finished Product) Downloaded from: http://www.planetstreetpainting.com/ * See ‘E:\p355\IMAGES\2d.like.3d.planetstreetpainting-4.jpg’ for the image. Psych 355, Miyamoto, Spr '15

The Ames Room Look at http://www.yorku.ca/eye/Ames%20room.htm Another example: http://presurfer.blogspot.com/2007_05_01_archive.html Video of the Ames Room Psych 355, Miyamoto, Spr '15

A Video Example of the Ames Room Errol & Ricky: http://www.youtube.com/watch?v=5ic7QGjGEX8 Where We Are Headed in the Perception Topic Psych 355, Miyamoto, Spr '15

Where We Are Headed in the Perception Topic The point made by the previous slides: Our perceptual system solves the inverse projection problem by applying various perceptual heuristics. Perceptual heuristics are strategies that provide “best guesses” about the stimulus object. Next: Gestalt Principles of Perception Gestalt Principles of Perception Psych 355, Miyamoto, Spr '15

Inverse Projection Problem Object could be created by the larger more distant rectangle or the tilted trapezoid. Inverse Project Problem: For any 2-dimensional image that is projected onto the retina, there are infinitely many different 3-dimensional shapes that could have produced that image. How does the mind decide which shape actually produced the 2-dimensional projected image? 26 Ambiguous Figures: The Ambiguous Box Psych 355, Miyamoto, Spr '15

The Gestalt Approach Emerged in early 20th century in response to structuralism. (Structuralism claimed that perception was bottom up – it was built up from simple, atomistic sensations.) Basic question of the Gestalt approach to perception: What principles govern the grouping of the components of a perceptual stimulus into an object or organized group of objects? Gestalt principles are sometimes called heuristics—these provide “best guesses” about the stimulus object. A heuristic is a “rule of thumb” that provides a best-guess solution to a problem. Gestalt laws do not always result in accurate perceptions of the environment. Contrast with algorithm, which is a procedure that is guaranteed to solve a problem. 27 Principle of Similarity Psych 355, Miyamoto, Spr '15

Gestalt Principle of Similarity Similar things are grouped together. Similarity in lightness, shape, color, size, and orientation cause grouping. a a a a a a a a b c d e f g b b b b b b b a b c d e f g c c c c c c c a b c d e f g d d d d d d d a b c d e f g e e e e e e e a b c d e f g f f f f f f f a b c d e f g g g g g g g g a b c d e f g (looks like rows) (looks like columns) Principle of Good Continuation Psych 355, Miyamoto, Spr '15

Gestalt Principle of Good Continuation Connected points result in smoothly curving lines. Points are seen as they belong together. Lines follows smooth path. Figure-Ground Principle Psych 355, Miyamoto, Spr '15

Figure-Ground Principle and the Principle of Smallness Face is Face is background foreground Figure/ground Principle – ambiguous figure The famous faces/vase figure. Principle of Smallness implies that we should see vases on the left and faces on the right Escher Print #1 Psych 355, Miyamoto, Spr '15

Figure-Ground Example Downloaded from http://www.worldofescher.com/gall ery/A41L.html Maurits Cornelis Escher Dutch graphics artist 1898 - 1972 Figure-ground problem: Separation of object from background Escher Print #2 Psych 355, Miyamoto, Spr '15

Another Figure-Ground Example Downloaded from http://www.worldofescher.com/gallery/A11L.html Principle of Common Fate Psych 355, Miyamoto, Spr '15

Tuesday, April 07, 2015: The Lecture Ended Here Psych 355, Miyamoto, Spr '15

Gestalt Principle: Common Fate Principle of common fate: Things that are moving in the same direction (at the same speed) appear to be grouped together. Go to website – look at it: http://tepserver.ucsd.edu/~jlevin/gp/time-example-common-fate/ This is a nice demonstration of the common fate principle. The groups of lines or shapes are only visible as a group when they are moving together. WARNING: The preceding demonstration requires a browser that has JAVA activated. I don’t understand the technicalities, but there are dangers (computer viruses) associated with the use of JAVA. If preceding example is not available, try http://www.georgemather.com/MotionDemos/KDEQT.html: Kinetic depth effect 34 P 355, Miyamoto, Winter '09 34 Examples of Gestalt Principle in Visual Design Psych 355, Miyamoto, Spr '15

Examples of Gestalt Principles in the World of Visual Design Principle of similarity implies that we see the three left figures as a group. Thus the right figure is an exception (anomaly) so it stands out. Principle of continuation: We "see" the motion of the leaf. Principle of Figure/Ground Principle of Simplicity Psych 355, Miyamoto, Spr '15 Summary: Evidence for Gestalt Principle of Perception - END

Goldstein Figure 3.21 What Gestalt principles are used here to create the illusion of a semi-transparent woman? Principle of Good Continuation Principle of Similarity Figure 3.21 Waves by Wilma Hurskainen Psych 355, Miyamoto, Spr '15

Goldstein Figure 3.21 What Gestalt principles are used here to create the illusion of a semi-transparent woman? Principle of Good Continuation Principle of Similarity Figure 3.21 Waves by Wilma Hurskainen Psych 355, Miyamoto, Spr '15

Summary – Evidence for Gestalt Principles of Perception Phenomenological support Experimental evidence – image segmentation (Not discussed in this lecture) Gestalt laws are perceptual heuristics Gestalt laws help to explain how the visual system solves the inverse projection problem (inferring a specific reality from ambiguous inputs). Important in the theory of object perception END Psych 355, Miyamoto, Spr '15