Psychology of Perception

Spring 2015
Warning: This is a dynamic syllabus. It gets updated as we go. Consult it several times a week on line.

Last Updated April 29, 2015

William M. Mace

Office: Life Sciences 212A

Office Hours: Monday 4:00 pm – 5:15 pm
Thursday 3 pm – 4 pm — and by appointment
Phone: X2343


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Trinity College Intellectual Honesty Policy

Students with Disabilities-
Trinity College complies with the Americans with Disabilities Act and Section 504 of the Rehabilitation Act. If you have a documented disability and require academic accommodations, please present your accommodations letter during my office hours over the first two weeks of the semester. If you do not have a letter, but have a disability requiring academic accommodations, or have questions about applying for academic accommodations, please contact Lori Clapis, Disability Coordinator, at 860-297-4025 or


The syllabus will be linked to Moodle. We may use Moodle more during the term, but most things will be linked to this webpage


Required Reading
All reading will be available online.

Webvision textbook. This has far more detail about the eye and vision than we will use. It is an excellent resource and some readings will be selected from it.

In order to pass the course, you must pass the class participation requirement and complete all assignments —exams, homework, and, for lab students, the Lab assignments and formal write-ups of assigned lab experiments. There will be three exams during the term and a final exam. The dates for these and the percentage of your grade determined by them will be:

With Lab Without Lab
Class Participation 10% 10%
Exam I February 18 10% 10%
Exam II March 9 15% 15%
Exam III April 22 20% 25%
Final Exam Monday, May 4, 9 a.m. 25% 40%
Labratory 20%
Seniors will take the Final Exam

Class participation: Your grade for class participation will take into account your attendance and your behavior. It is assumed that you will show normal courtesy to other classmates and arrive on time, then stay in your seat for the entire class. It’s only 50 minutes. Once in a while the class will be asked questions about what’s been covered in the current class, the previous class, or a salient reading. There also will be opportunities for students to clarify any questions that are unclear. Students who do not volunteer to answer questions in class may be called on. Occasionally, there will be short homework assignments and correspondence by email. Satisfactory participation in these also will count in the category of class participation. The point will be to help me stay in touch with what you are picking up, to increase the chances you will know the material well before exam cramming time.

Exams will consist of questions with short answers. Questions will depend on both classes and reading. You will not do well if you concentrate only on the reading or only on the classes. Moreover, the question usually will ask you to figure out the answer based on what you learned and not merely to repeat something you heard or read. I want you to understand how things work. Your goal should be to make the material make sense to you. If it does not, you need to ask questions — ask in class, after class, over electronic mail, or any other time you can reach me.

For lab students there will be formal writeups to do based on data collected in labs. Data and short assignments based on labs will be due whenever data are collected from lab experiments. As you can deduce from above, your lab grade will contribute 20% of your total grade.

The syllabus for this course is online. The address is:

Schedule of Classes

Date Reading for Class Topic description

What the topic, “Perception,” is about

Class 1

January 21

Causality: What causes what? And here? A little to big effect.

Light from the stars — things to think about. “Our galaxy has a diameter somewhere around 100,000 light years.” One light year is around 6 trillion miles. [a trillion is 1,000,000,000,000]. See also: How far is that?

Framework for thinking about perception

The Electromagnetic spectrum (Broken link)  All of these kinds of radiation are different and have widely different uses, but they also are the SAME. In what way? They are the SAME as electromagnetic radiation. They are DIFFERENT in wavelength and frequency. Click HERE to learn about the wavelength and frequency property of all waves. Note that SOUND waves are NOT electromagnetic waves and are not on the list of types of electromagnetic radiation. Sound is based on the actual mechanical vibration of molecules in the air that eventually move your tympanic membrane (ear drum) back and forth. That means that sound cannot travel in a vacuum, where there are no molecules. Light travels through outer space, sound does not.

Richard Feynman reflecting on vision and the electromagnetic spectrum HERE

See assignment at beginning of the next syllabus entry!

Perception is how we find out about the world through seeing, hearing, touching, tasting, and smelling. Without perceiving, we have nothing to remember and nothing to talk about. Without perceiving, we could not be in touch with our world — and could not exist. To know what is in the world, and where you are in it, at every moment, depends on perceiving. Are you hungry? That is perceiving. Where is something to eat? How do you get it? How do you know that you are eating? All of those things involve perceiving. The topic is a great challenge to science because so much of what we know we have to figure out does not necessarily answer our fundamental questions about how perceiving can work.Perception, as a topic, is totally interdisciplinary. I have colleagues engaged in trying to understand perception in the following areas (in no particular order) –philosophy, biology, neuroscience, physics, chemistry, engineering, robotics, arts, painting, sculpture, architecture, film. Mathematics, physical therapy, kinesiology, computer vision, computer animation, video games. Within psychology, social, developmental, memory, human factors, design. We won’t cover all of those, but if you have special interests in any of those, please let me know.

Bookkeeping in the course
Even though our major source of light is from the sun (a star among how many stars?), we do not “see stars” most of the time. We see the earth and what populates it. Do we have principles for seeing the substantial earth, as opposed to light alone?

 Class 2January 23 Do the reading and watch the videos before class TODAY: Watch the 2 videos below then 1. answer the question: Do you see the world as it really is? 2. write out 3 [three total] relevant quotes from the videos. Tell me where each quote came from as precisely as you can. Send your work to me on Moodle by 10 pm Sunday night (Jan. 25).

How to find the Video — go to “Films on Demand” in the Trinity Online Resources section of the Library website and, under “Psychology > Biological Psychology > Sensation and Perception,” find the video, “Is Seeing Believing? New Frontiers in the Science of the Senses.”

Beau Lotto TED talk

Video: Is Seeing Believing? [Mainly sections 1, 2, and 7 — out of 23]

Framework for thinking about perception


Bulthoff group

Richard Gregory’s statement of the fundmental problem.

Gregory — representative paper
Gregory Remembered

Notes elaborating first two classes

 Ambiguity. When a shape, for example, is ambiguous, that means that it has more than one interpretation. The sensitive part of the back of the eyeball is called the retina. You’ll hear a lot about it. The first important fact about the retina is that it is flat. The 3D layout of the world is projected onto this flat surface. This results in supposedly infinite ambiguity. That’s one theory anyway. The persistent puzzle is that our everyday world is not as ambiguous as some scientists think. Why? [This is a big question and won’t get an easy answer]
Class 3

January 26

Notes elaborating first two classes

Continue readings from last time

High School Video for example

High School Video reply — Seattle suburbs

Purves figure that you can manipulate

Richard Gregory’s statement of the fundmental problem.
Gregory remembered

Course Framework — linked again. Same as Jan. 21 and 23 item.

The Gibsons developed what is called The Ecological Approach. Their reply to Gregory is a short précis backed by many years’ work.Gibson’s reply to Gregory

Figure with Gibsons’ paper

When you experience an illusion, how do you know it is an illusion?

 The Causal Theory of Perception — or “Where did the light go?” For that matter: “Where did the environment go?”


Class 4

January 28

Tufte signs — This is to make the point about the 2 different meanings of the word “size.” Just as the Purves (Lotto) figure makes the same point about two meanings of “color.” Ask questions if you don’t follow this in class.

Newton’s Opticks. (4th edition, 1730). Page numbers are in square brackets on the right. For one of the most famous quotes, see p. 125, the paragraph labeled “Definition.”

Here is the main quote highlighted in the famous paragraph from the above.

1. Electromagnetic spectrum

2. BU website on ADDITIVE color “mixing.”

 Light, color, the eye and SENSATION; Johannes Müller’s Specific Nerve Energies. “The rays are not colored.” What??!
Class 5

January 30

Newton’s Opticks. (4th edition, 1730). Page numbers are in square brackets on the right. For one of the most famous quotes, see p. 125, the paragraph labeled “Definition.”

Here is the main quote highlighted in the famous paragraph from the above.

1. Electromagnetic spectrum

2. BU website on ADDITIVE color “mixing.”

3. Newton Demonstration
4. Light and Color Introduction (QUESTION)
5.Two kinds of color “mixing” illustrated again Pay attention first only to the left side where “additive” mixing is demonstrated.

Open a PowerPoint file to see another place where you can experiment with additive mixing.

 Wavelength is physics; color is psychology (experience)In color, what is GIVEN? What is GOT?
Class 6

February 2


Explore what you can do with mixing colors on PowerPoint.

Class 7

February 4

Number 4 from Jan. 30 — Light and Color Introduction

Color section of the Web book. Read the Introduction very carefully. It is a priceless statement.

I have not yet assigned to you this entire article (only the 3 Introductory paragraphs). BUT, if you will scroll through this entire color article, you will see that there are no references to surfaces that reflect light in the entire article. What does the author imply is GIVEN? What is GOT? Notice also what is in Figures 1A and Figure 15.

Two kinds of color “mixing” illustrated again — From Michael Bach website Pay attention first only to the left side where “additive” mixing is demonstrated. This is a repeat of display 5 above. This is the MOST useful interactive demonstration because it allows you to manipulate and study the results of both additive and subtractive “mixing” in the same display. PLAY WITH it a lot and study what happens. Studying what happens with many different conditions on this display is one of the best uses of your study time.

You should also know the material in the pages linked to #4 above as well.

Powerpoint color based mixing assignment

Due Friday, Feb. 6.

Note that you will submit ONE SLIDE of a PowerPoint file and that the name of your file should begin with your last name. Submit your PowerPoint on Moodle.

Class 8

February 6

Learning about SUBTRACTION of wavelengths through filters.

Study the right hand side of the interactive color display by Michael Bach Michael Bach website

Color Samples to show effect of filters in class

What happens if we additively mix 3 very narrow band wavelengths? Say 440 nm, 575 nm and 620 nm.

What is a metamer?

rgb Homework due today


Class 9

February 9

One example website with rgb colors and names

Our color name results

Averages for our rgb values in matching papers

Class 10
February 11

Color swatches for orange set

Lighting from GE. Try looking at the spectra. Look at sodium vapor last. READ: Main Heading, “Learn about Light.” Then links to each of the subsections under the “Learn about Light” heading. For our Perception class, pay special attention to the subsections about seeing light, including “Matching” and “Adaptation.”

Interesting wording to examine. Spider vision article.

Edmunds filter data — Excel spreadsheet

Some more graphs of the filters

Detailed review: The spectrum as numbers vs.
The spectrum as color experience.
How the difference implies METAMERS.
Class 11
February 13
Review of last classes.

What you should know now

Class 12
February 16
Class 13
February 18
Exam I


Class 14
February 20
Single wavelength, single visual pigment matching

Full presentation of cone pigment logic (THIS LINK LEADS TO AN ONLINE POWERPOINT???). If you cannot read this file, you can get the original PowerPoint here.

See also Figure 14 in the section linked next.

Read about Photoreceptors [only]

Facts and figures about human retina. From the end of the online vision book.

Wavelength (physical) and color (psychological)

What happens if we additively mix 3 very narrow band wavelengths? Say 440 nm, 575 nm and 620 nm.

What is a metamer?

Beginning discussion of details of relation between number of underlying pigments in the retina and number of wavelengths that can be discriminated.

Finishing details about how 3 pigments work with respect to matching experiments

Keep track of where these numbers are. You don’t have to remember the numbers, but I do want you to know where you can find them.

 Class 15
February 23
Today’s topic in class is detailed look at consequences of the absorption curve for rhodopsin.

Full presentation of cone pigment logic Expanded version.

Single wavelength, single visual pigment matching

Class 16
February 25
Full presentation of cone pigment logic.Expanded version.

Three cone pigment absorption curves

See also Figure 14 in the section linked next.

Read about Photoreceptors [only]

Facts and figures about human retina. From the end of the online vision book.

 Full cone pigment logic and matching experiments

More about colors of the Rainbow. What we know based on COLOR APPEARANCE.

Class 17
March 2[Friday was a Trinity Day]
Updated PowerPoint on “The Dress”.

Opponent Color Powerpoint

Opponent processes (ONLINE POWERPOINT)

Read: Hurvich, L. & Jameson, D. (1974). Opponent Processes as a model for neural organization. American Psychologist, 29(2) 88 – 102.

Color II. Goethe, Hering, and Hurvich & Jameson.Finishing Opponent Processes.
Explaining the Hurvich and Jameson measurements of opponent colorsOpponent processes: How is color EXPERIENCE organized?Full presentation of Opponent Process theory
 Class 18
March 4
 Carefully complete Opponent Process theory and be sure to understand Hurvich & Jameson cancellation experiment in relation to their graphs of wavelength color appearances.
 Class 19
March 6
 Review for exam
 Class 20
March 9
 Class 21
March 11
The 6 topics covered on Exam 3 are indicated in upper case text from here to April 17. The course material pertinent to the topic is everything listed after what is in upper case until you get to the next upper case listing.


Circle Demo

For now, READ ONLY to the top of p. 798 of Gilchrist’s paper. We’ll return to it later. Pay special attention to the “ratio principle” of Wallach.

Contrast: Neutral colorPurves Demo that you saw in videos at the beginning of the course.

Black and white demo on screen — where does “black” come from?

Nonspectral colors — Black and white, and all the grays in between are called neutral colors.

Perceptual Constancy in color and lightness. Black and White. Classic work of Wallach and recent work of Gilchrist.

Continuing introduction of neutral colors,

lightness, and lightness constancy

Appearance of one area can depend heavily on the appearance of neighboring areas.

What does it mean to say the luminance is ambiguous?

Review the main points of Gilchrist

Class 22
March 13Next class is after spring break
Gilchrist paper on lightness perception

In order to dramatize the concept of luminance (amount of light at the eye), which is so important in Gilchrist, we will use our own luminance meter in class.

Tufte signs This picture of the signs on Tufte’s estate shows pictorial or retinal adjacency, but they signs are on different planes (at different distances from the observere) in the world. This means that they are adjacent at the eye, but NOT in the world.

 Moving ahead to get back to hues and “color constancy.”
Class 23
March 23
Last time we learned about luminance and its measurement with a luminance meter. Basically LUMINANCE is a measure of amount of light coming to the eye from a place on a surface.

Gilchrist paper on lightness perception If you cannot get the whole paper from this link, go to the class Moodle site, Topic 4 to find a copy.

Gilchrist full PowerPonit on lightness perception and the ANCHORING problem

 Class 24
March 25


Read: Land’s Retinex Paper

Illustrating Land’s “Mondrian” experiment

Units of light measurement in Land’s Retinex demonstrations are in milliwatts per steradian per square meter. So here’s a steradian.

Land’s Retinex Theory

Real Mondrians paintings look like.

Color constancy with Edwin Land.


Land’s Red – White experiment More Land. I now give you the option of reviewing the black and white slides we saw in class, for the Land Red – White demo.   Elaborating the Land Red and White experiment to segue into Retinex demonstrations and theory.

Retinex theory

 Class 25
March 27
Land himself explaining demos (VIDEO HAS BEEN REMOVED) For our purposes, think of this beginning at the 3:39 mark in the video.

Details of Retinex demonstration, with Mondrians

Harvard art project with light on Rothko paintings

Land Mondrian Homework (ONLINE POWERPOINT)

Due next Wednesday at 5 pm

 Class 26
March 30
Land’s full Retinex Theory [See links for March 25]

PhotoFlair by TruView uses the retinex algorithm and advertises that it comes from NASA

Class 27

April 1

 Land final Reviewing Land’s neutral color algorithm

Land Homework due


 Class 28
April 3

The retina from your online book on the eye.

Orienting slides, retina to cortex through lateral geniculate nucleus (LGN)

Hubel and Wiesel Class slides 


Hubel book Good resource

 Class today concentrates on the work of Kuffler and the discovery of RECEPTIVE FIELDS. In Kuffler’s case, we were looking at the receptive fields of retinal ganglion cells — ON-CENTER, OFF SURROUND; and OFF-CENTER, ON SURROUND. We foreshadowed the Nobel prize of Hubel & Wiesel.
 Class 29
April 6
Advising Week

Hubel & Wiesel Discovery

Visual Cortex in online Webvision book

Hubel & Wiesel simple cell video

Diagrams of areas of visual cortex from George Mather.


Lateral inhibition

Chevreul Illusion demo. Also called “Mach Bands.” This is most famously presented as an example of Mach Bands, but some people prefer Chevreul because he was first

A Chevreul that you can manipulate 

A simple lateral inhibition practice case.. 

 Class 30
April 8
Chapter 3 of Hubel book is excellent review of the brain study that we have done to here.

Chapter 4 of Hubel book covers the primary visual cortex


Monkey Paw cells in Inferior Temporal Cortex (IT)

 Class 31
April 10
Photo sample  Where are lines?
Part of photo 
Blow-up within part of photo Lines?Charles Gross’s description of discoveriesGross and colleagues’ face workQuian Quiroga et alFigure 1 from Quian Quiroga et al

Signal Detection graphs in Quian Quiroga et al

Figure showing MTL brain region

Brain wiring debate: Seung vs. Movshon. Introductions last for a while. Really begins about 10 minutes in. There are many references to C. elegans in the video. Here is what that’s about

 Class 32
April 13
Quian Quiroga et al

Figure 1 from Quian Quiroga et al

Signal Detection graphs in Quian Quiroga et al

Figure showing MTL brain region

Gestalt Psychology!

Class 33
April 15

Wertheimer (1923) on Gestalt psychology

Same as above Better view of text, not of diagrams.

Common Gestalt Demo

There are two papers about Gestalt psychology by Mary Henle on the Moodle site. They are required reading!

Gestalt is NOT someone’s name

Gestalt theme: Organization in Perception. Need to EXPLAIN THE OBVIOUS.

Gestalt Mantra: “The whole is greater than the sum of its parts”

Class 34
April 17
Gestalt psychology and binocular vision, culminating in the work of Bela Julesz


Seeing with 2 eyes — Bela Julesz and binocular vision

Binocular vision tutorial in pdf.

Random Dot Stereograms as puzzles for the Gestalt account of binocular fusion

Binocular test for Evan

Introducing Ecological Psychology


Class 35
April 20

Introduction to Ecological Psychology

Motion — What is the classical ambiguity of motion perception when motion is treated as points on the retina? What is the ecological alternative?
Class 36
April 22
 Class 37
April 24
From last time — maximum motion ambiguity when the eye is the frame of reference vs. increased specificity when the world is the frame of reference.

Global Optic Flow — the geometric information for SELF-MOVEMENT in the environment. This is well illustrated in videos of airplane landings from the point of view of the pilot.

KLM Boeing B747-400 Landing St. Maarten

David N. Lee constructed a SWINGING ROOM to study the perception of self-movement by manipulating GLOBAL OPTIC FLOW. Visual control of self-movement is important in simply maintaing upright posture, i.e. balance.

Perception and Action Lee Film  excerpt

Entire Lee FilmBBC video on movement [Start at 1:14] From Gert-Jan Pepping’s YouTube collection. You can see some related videos in the same set.

Dave Lee’s Perception Movement Action Research Consortium

Dave Lee over the years

Barrie Frost Visual Neurophysiology of optic flow.

Zoomquilt a good example of self motion through a stable environment. Optic flow is here — and more.

Class demo of catching 1

Class demo of catching 2

Gannets diving

Lee and Reddish on diving gannets

Lee and students on the Long Jump

Horizon Link Horizon photo. Most of class this day was about the horizon relations — determining the direction of the point of view, and the sizes of things relative to the height of the point of view.

Gannet and Tau detail Lee’s tau is a relation at the eye that specifies time of gap closure (time to contact). Tau is only about the case of constant velocity. Falling under the force of gravity (like the gannets) involves acceleration, a consistent change of velocity. Lee’s idea in the paper is that the gannets still monitor tau, but that they keep checking it until tau reaches a key value that he calls tau margin.

Lee and Reddish on diving gannets

Lee and students on the Long Jump

Introduction to Ecological Approach


Optic Flow


perception as answering questions
vs. acting in the world

After optic flow, Dave Lee’s Tau
and its significance — a “higher
order” variable that specifies “time
to contact.” A very important
feature of Tau is that it focuses on
GAPS as objects and gap closing.
Especially the TIMING of gap closing.
Intentional tasks in a real
environment can be looked at as
being about gap closing ON TIME.




Long Jump

The view of the plane landing
shows global optic flow, which specifies
that the observer is moving, not the world.
It is not ambiguous the way pointwise motion
on the eyeball is (see the last two slides on
the slide, “Introduction to Ecological Approach”).

Class 38
April 27
Review Lee Film, beginning with babies in swinging room

Gannet and tau detail

More detail on tau.

Introduction to Ecological Approach, emphasizing perceiving the environment, ecological realism.

Seeing yourself move in the world
David Lee Film

Class 39
April 29
Introduction to Ecological Approach (same as before) Beau Lotto and Richard Gregory STARTED from ambiguity in optical patterns. At bottom, everything is the same. For Gibson, at bottom, every point of view is DIFFERENT (and therefore specific). Properties of he world and our activity in the world are there to be discovered.

Horizon Link Horizon photo. Horizon relations — determining the direction of the point of view, and the sizes of things relative to the height of the point of view. Also — see the horizon and horizon relations in the airplane landing video and Lee’s car driving scenes.

Gibson 1975 summary of research

Mace & Heft Read Encyclopedia article



FINAL EXAM Monday MAY 4, 9 a.m. Regular Classroom