Looking with the Head and Eyes (Gibson, 1979, Chapter 12)

In this chapter, Gibson places head and eye movements on an ecological footing, and makes them the activity of a distributed perceptual system (c.f. Gibson, 1966) who's job it is to look around. 

We have to look around because our heads get in the way of our eyes. Even animals with eyes on the side have this problem, but for animals with front-facing eyes over half the optic array that is ambient to a point of observation is occluded by the head (which of course also specifies the presence of the self). Looking around is about reversing that occlusion and revealing things as required. 

The Discovery of the Occluding Edge and Its Implications for Perception (Gibson, 1979, Chapter 11)

Gibson introduced us to the notion of occlusion in Chapter 5. Occlusion is when one surface is progressively covered up by another surface, and the details of how optical texture is deleted specifies the occluding edge and the fact that occlusion is happening. In this chapter, Gibson details the radical implications of this fact of the optic array for theories of perception. Most importantly, given occlusion, vision cannot be based on images, series of images, or perspective structure, and it is not limited to working when sensations fall on the retina. Vision is a process that extends back and forwards in time, and this is enabled by information. 

Experiments on the Perception of Motion in the World and Movement of the Self (Gibson, 1979, Chapter 10)

Chapter 9 was about perceiving persistence in the environment. Chapter 10 is about perceiving change, and the evidence that this also might be direct. 

In contrast to retinal image based theories, Gibson proposes that change is perceived because of 'disturbances of structure in the ambient array' (pg 162). A key point here is that 'Disturbances of structure can specify events without being similar to them' (pg 162); this is a key fact about information. It does not get its meaning because it is somehow a copy of the world; it gets its meaning because of the laws that govern it's creation. 

Experimental Evidence for Direct Perception: Persisting Layout (Gibson, 1979, Chapter 9)

We've now completed the first two sections of the book, which lay out the ecological approach. Gibson now turns to a review of the (at the time) existing empirical evidence for the various claims he has made. The first chapter focuses on how information supports the perception of a persisting layout of surfaces.

The Theory of Affordances (Gibson, 1979, Chapter 8)

The most influential part of this book is the theory of affordances. We still argue a lot about what these are and how they work, because they are slightly weird (at least from the traditional point of view). So it was interesting to go back and read Gibson's original approach. I was struck by how much sense it makes in the context of the previous chapters; the book really builds and develops and this chapter should be discussed in that context I think.

Environments are the surfaces that separate substances from the medium. But these configurations of surfaces aren't simply there; they offer possibilities for action. They afford things to the animal. Gibson asks 

How do we go from surfaces to affordances? And if there is information in light for the perception of surfaces, is there information for the perception of what they afford? Perhaps the composition and layout of surfaces constitute what they afford. If so, to perceive them is to perceive what they afford. This is a radical hypothesis...

pg 119

In this chapter, Gibson does not offer a single straight-forward definition; that's not really how this works. Instead he lays out examples, and uses those to constrain the concept. As usual, ecological categories have fuzzy boundaries and this is ok!

The Optical Information for Self-Perception (Gibson, 1979, Chapter 7)

So far we have considered what the world looks like to a point of observation that may or may not be occupied. It was important to Gibson that he establish that the optic array available at such a point is public, not private, and so can be shared across individuals (see Chapter 1 for the problem and 3 for the solution). In this chapter, Gibson asks what is seen by an individual when they occupy a point of observation, and in this case there is some privately available information that specifies things about the self. 

Events and the Information for Perceiving Events (Gibson, 1979, Chapter 6)

In the previous chapter, Gibson introduced the notion of the ambient optic array and discussed the kinds of information it can have (flow, and invariants). The focus there was what is revealed by a moving observer. This chapter is about what is revealed as the environment changes; when events occur. 

Sabrina blogged this chapter here and here. 

The Ambient Optic Array (Gibson, 1979, Chapter 5)

In the previous chapter, Gibson laid the foundations for an ecological optics by distinguishing between stimulation and stimulus information. In this chapter, he lays out the details of how to analyse the source of visual stimulus information, as an ambient optic array that contains both invariant and perspective (variant) structure. 

Sabrina blogged this chapter here, here, and here; there is a lot going on in this chapter!

The Relationship Between Stimulation and Stimulus Information (Gibson, 1979, Chapter 4)

The first three chapters describe the world to be perceived, at the ecological scale. This chapter opens the section on how we visually perceive that world - via information. Remember, a key part of the ecological analysis is doing things in this order (see the Introduction). 

The work of the next few chapters is to lay out a theory of ecological optics. Lots of science studies light, but as with the physical world/environment distinction, Gibson will insist on distinguishing between the physics of light and the ecology of it; only the latter will be relevant to a theory of perception. 

Sabrina also blogged this chapter here. 

The Meaningful Environment (Gibson, 1979, Chapter 3)

In Chapter 1, Gibson identified the animal and it's environment as the two mutually defining parts of an ecological system. In Chapter 2, he developed a vocabulary for describing an environment (as opposed to the physical world). Now, in Chapter 3, he will use that vocabulary to identify that the environment of an animal is meaningful, literally full of meaning, and this will mean that meaning is there to be discovered, rather than constructed (as in every theory of perception so far). 

Sabrina also blogged this chapter here. 

Medium, Substances, Surfaces (Gibson, 1979, Chapter 2)

In this chapter, Gibson continues to lay out the rules of the environment (vs the physical world). In physics, there are objects in spaces, but this simply does not work as the basis of perception (see the chapters about Helmholtz and the limits of unconscious inference in the Turvey book). Instead, environments are made of medium, substances, and surfaces, and this chapter defines these at the ecological scale.

This chapter introduces a lot of vocabulary for talking about the environment: I have reviewed some of it, but see the chapter for the full set because it is going to be needed as we described the environment to be perceived. 

Note: Sabrina also blogged this chapter here.

The Animal and the Environment (Gibson, 1979, Chapter 1)

Gibson's first chapter introduces his notion of the environment. This is a distinct level of description from the world according to physics, even though everything in it is still made of physical stuff. The environment is the ecologically-scaled surroundings to an organism, and Gibson lays out some of the key differences between this and the physical world here. Why? Because perceiving is going to be of the environment, and not of the physical world, and as we progress this is what the word 'environment' will mean.

Note: Sabrina also blogged this chapter here.

Introductions in the 2014 Edition (Gibson, 1979 Reading Group)

The 2014 reprint of Gibson (1979) includes the original Preface and Introduction, as well as an Introduction to the Classic Edition by William H Mace. A few things come up in Gibson's sections that I thought were cool, and worth documenting as part of the reading group. 

Mace's Introduction does some nice work reviewing Gibson's intellectual development over the course of his career and exemplified by his three books. He points to how the ecological approach has grown and connected to other fields in the years since Gibson's death, and talks about how the 1979 book was received (a mixed bag, to say the least!). It's a good read, but it doesn't have much new content in it so for this reading group I'll just focus on the bits Gibson says that set things up nicely. 

Reading Group - Gibson (1979) The Ecological Approach to Visual Perception

Rob, Marianne, and I had so much fun with the Turvey (2019) reading group that we decided to keep going, and we decided to return to the source - Gibson's 1979 book. Buckle up, this should be fun!

We'll be using the 2014 edition, so all page numbers will refer to that (I have the feeling I will be directly quoting the eminently quotable Gibson a lot more than I did with Turvey!). I will use this page to link to my post, and the video and podcast links for our group discussions, for each chapter.

Gibson (1979) The Ecological Approach to Visual Perception

Introductions in the 2014 edition

Part I: The Environment to be Perceived

Chapter 1: The Animal and the Environment

Chapter 2: Medium, Substances, Surfaces

    Chapters 1 & 2: Video || Podcast

Chapter 3: The Meaningful Environment  

Part II: The Information for Visual Perception

Chapter 4: The Relationship Between Stimulation and Stimulus Information  

    Chapters 3 & 4: Video || Podcast

Chapter 5: The Ambient Optic Array

    Chapter 5: Video || Podcast 

Chapter 6: Events and the Information for Perceiving Events  

Chapter 7: The Optical Information for Self-Perception  

    Chapters 6 & 7: Video || Podcast

Chapter 8: The Theory of Affordances

    Chapter 8: Video || Podcast

Part III: Visual Perception

Chapter 9: Experimental Evidence for Direct Perception: Persisting Layout 

    Chapter 9: Video || Podcast

Chapter 10: Experiments on the Perception of Motion in the World and Movement of the Self  

    Chapter 10: Video || Podcast

Chapter 11: The Discovery of the Occluding Edge and Its Implications for Perception  

    Chapter 11: Video || Podcast

Chapter 12: Looking with the Head and Eyes  

    Chapters 12: Video || Podcast

Chapter 13: Locomotion and Manipulation  

Chapter 14: The Theory of Information Pickup and Its Consequences  

    Chapters 13 & 14: Video || Podcast

Part IV: Depiction

Chapter 15: Pictures and Visual Awareness  

Chapter 16: Motion Pictures and Visual Awareness  

    Chapters 15 & 16: Video || Podcast

Turvey, Lectures on Perception: The Story So Far

I have now reviewed the first 7 Lectures on Perception from Turvey' textbook (posts indexed here). I feel like I've reached a natural pause point before carrying on with the rest of the lectures, and I wanted to summarise what I thought has been going on so far.

These are lectures on perception, quite generally. While Turvey will explain the ecological approach, that's not what is currently going on. Right now Turvey is laying out the scope of the question 'what kind of material system could be a perceiving system?' and reviewing the typical, non-ecological answers to that question.

The main takeaway at this point is that we have been trying to answer that question using 17th century notions of material systems, specifically Newtonian mechanics. This has placed what turn out to be unacceptable restrictions on the kinds of properties we are allowed to invoke, and theories of perception have had to fill the gaps with unpayable 'loans of intelligence'. 21st century physics, however, has more on offer; complexity science and quantum mechanics teach us many valuable lessons on how to expand our horizons so that perception becomes possible, rather than miraculous. 

Lecture 2: Organism-Environment Dualism (Turvey, 2019, Lectures on Perception)

In this Lecture, Turvey lays out the organism-environment dualism that lies at the heart of pretty much all attempts to answer the question, how can an organism come to know about it's environment via perception? He discusses Descartes' mechanistic (mechanical) approach, and then pivots back to the idea that Composition, Environment, Structures (CES) systems are the only approach that can possibly cope with the nature of the problem. 

Lecture 1: What Kind of Systems Do We Study? (Turvey, 2019, Lectures on Perception)

The first thing to do is to characterise what it is we are studying when we are studying perception. Turvey states we are studying epistemic, intentional systems and spends this chapter explaining each term. He does the most work on system; intentional and epistemic are primarily just defined and noted as being features of the system we are going to have to engage with. 

As usual, I will try to efficiently review the key points and then add some reflections on what the chapter made me think about. 

Reading Group: Turvey (2019), Lectures on Perception

Michael Turvey ran a famously intense graduate level class on perception and action at CESPA. He has recently, finally, published a book of his lectures, in which he basically develops the ecological approach to perception-action from first principles. 

It's taken a while, but I have produced a series of posts, one lecture at a time. In each post, I attempted to (concisely) summarise the key points from the lecture. At the end, I reflected on what I've learned from the lecture, and connect it to issues in the literature. 

I would never have finished this if I hadn't been working with Rob Gray and Marianne Davis on the Perception-Action Podcast. I have linked to the Youtube video recordings and the audio podcast versions of our discussions below. 

Links to posts

Lecture 1: What Kind of Systems Do We Study?

Lecture 2: Organism-Environment Dualism

• Perception-Action Podcast episode on Lectures 1 & 2: Video  Podcast

Lecture 3: Direct Perceiving, Indirect Perceiving

Lecture 4: Simulative, Projective, and Locality Assumptions

• Perception-Action Podcast episode on Lectures 3 & 4: Video  Podcast

Lecture 5: The Mechanistic Hypothesis

Lecture 6: The Cartesian Program

• Perception-Action Podcast episode on Lectures 5 & 6: Video  Podcast

Lecture 7: Empiricism and the Man in the Inner Room

The Story So Far

Lecture 8: The Space Enigmas I: Berkeley

• Perception-Action Podcast episode on Lectures 7 & 8: Video  Podcast

Lecture 9: The Space Enigmas II: Kant, the Nature of Geometry, and the Geometry of Nature

Lecture 10: The Space Enigmas III: Local Signs and Geometrical Empiricism

• Perception-Action Podcast episode on Lectures 9 & 10: Video  Podcast

Lecture 11: Doctrines of Sensations and Unconscious Inferences

Lecture 12: The Space Enigmas IV: On Learning Space Perception

• Perception-Action Podcast episode on Lectures 11 & 12: Video Podcast

Lecture 13: Gestaltism I: Atomism, Anatomism, and Mechanical Order

Lecture 14: Gestaltism II: Fields, Self-Organization, and the Invariance Postulate of Evolution

• Perception-Action Podcast episode on Lectures 13 & 14: Video Podcast

Lecture 15: Gestaltism III: Experience error, CNS error, Psych-neural Isomorphism, Behavioural Environment

Lecture 16: The Computational-Representational Perspective: Preliminaries

• Perception-Action Podcast episode on Lectures 15 & 16: Video Podcast

Lecture 17: Pattern Recognition and Representation Bearers

Lecture 18: Turing Reductionism, Token Physicalism: The Computational System Assumption

Lecture 19: Reflections on the Physical Symbol System Hypothesis

• Perception-Action Podcast episode on Lectures 17, 18 & 19: Video Podcast

Lecture 20: Ecology: The Science that Reasons Why

Lecture 21: Barriers to Ecological Realism

• Perception-Action Podcast episode on Lectures 20 & 21: Video Podcast

Lecture 22: Ontology at the Ecological Scale

Lecture 23: Ecological Optics Primer

• Perception-Action Podcast on Lectures 22 and 23: Video Podcast

Lecture 24: Perceiving "How to Get About Among Things"

Lecture 25: The Mechanical Basis for "Getting About Among Things"

• Perception-Action Podcast on Lectures 24 and 25: Video Podcast

Lecture 26: Strong Anticipation and Direct Perception

• Perception-Action Podcast on Lecture 26, plus summary: Video Podcast

#MechanismWeek (a week of posts commencing June 20th 2016)

Cognitive science is, in principle, the search to understand the mechanisms that cause our behaviour to look the way that it does. We run experiments designed to figure out the form of the behaviour to be explained, and we propose models that try to account for the behaviour. But how well are we doing, and can we do better?

It turns out that there is a rich and extremely useful philosophical literature about mechanisms. Specifically, there is a lot of clear and accessible work describing what mechanisms are, and, more importantly, how science can go about modelling those mechanisms. This literature has provided us with a wonderfully useful central focus for our ongoing work, and I wanted to walk through the key issues here. (We have covered this topic in a couple of posts - here and here - but there are several interlocking issues that I want to spell out one at a time).

Sabrina is in Warsaw June 23-25th attending the Mechanistic Integration and Unification in Cognitive Science conference, where she will present on how ecological information provides the key to mechanistic explanations in psychology.

To celebrate, there will be a new post from her every day of the week commencing June 20th 2016 on the topic of mechanisms, specifically cognitive mechanisms, and how to model them. Below is a list describing the upcoming posts and providing links to some useful reading.

We'd like to invite you all to play along, either in the comments or on Twitter (where we live as @PsychScientists; suggested hashtag #MechanismWeek). I've sketched out the week below, with recommended readings so yo can play along.

Chemero (2009) Chapter 9 - The Metaphysics of Radical Embodiment

The final chapter of RECS tackles the metaphysical implications of the radical stance. Gibson was a staunch realist, but there are some odd elements to entities like affordances that, to certain minds, sound like idealism or antirealism of some kind. Realism is, essentially, the claim that there is a world independent of our experience of it, and that we can have basically accurate knowledge of that external world. In modern times this reality has been equated with the description given by physics. Affordances don't belong to physics, however; whether relations or dispositions, they are, at heart, facts which span the organism and the environment. This sounds wrong to a lot of ears (as Ken's comments on that post readily show!). Chemero therefore devotes the final chapter to defending the claim that RECS can be realist; this matters, because people tend not to like idealism in their science these days, and it's going to be a standard philosophical objection to the RECS programme if not addressed.