Affordance Analysis
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[edit] Introduction to Affordance Analysis
The book which started Affordance Analysis in Computer Science was:
- Norman, Donald A. (1988/2002). The Design of Everyday Things. Originally published as The Psychology of Everyday Things. Basic Books: New York.
It is easy to read, and highly recommended for anyone interested in design. Donald Norman is a Cognitive Scientist, so it is written more from a Cognitive perspective than an engineering perspective, but this makes the lessons contained in the book no less relevant.
The term "Affordance" was originally coined by the Cognitive Scientist James J. Gibson in order to describe one manner in which the brain might analyze information contained within the world. See the subsection What is an Affordance? for a more detailed discussion of this definition of an Affordance.
Donald A. Norman used the term "affordance" to describe how we automatically associate certain structures in the physical world with certain actions: A plate on a door means "push here" even if nothing is written on it, for example. Norman was not concerned with whether these affordances were due to inherrent structures in the brain, or whether they were the results of cultural training, or came from some other source. His point was simply that they were one thing which could be used by designers to communicate proper usage of an item (and avoided when they would communicate improper usage).
[edit] Use of Affordance Analysis
Computer Scientists use Affordance Analysis to analyze properties of items and computer programs in order to figure out what these items or programs inherently facilitate, and what they do not, simply by the nature of their structure. For example, when comparing the use of pen and paper for note-taking to using a laptop, one might note that pen and paper are cheap, easy to use to draw pictures and diagrams, easy to loose or misplace, and the information needs to be recopied in order to be edited, etc. The Laptop is quick to type, easy to read the typed results, hard to use to draw pictures, digitally preserved data is easy to transfer, edit, etc.
Affordance Analysis is often best done in a group in a brainstorming session. There are several types of affordances, including:
- Input Affordances
- Output Affordances
- Process Affordances
All of which can be considered from two perspectives:
- Physical Affordances
- Social Affordances
Neither SBD nor Affordance Analysis is an exhaustive method of analysis, but they can help to inform design by inspiring creativity, uncovering major problems with a design before it has been built, etc. They are useful as brainstorming tools, where scenarios and personas focus on what people will do in a particular situation, and Affordance Analysis focuses on physical and functional properties of items, situations, processes etc.
[edit] References
In chronological order (more or less).
Gibson, J.J. (1979). The Ecological Approach to Visual Perception, Houghton Mifflin, Boston. (Currently published by Lawrence Eribaum, Hillsdale, NJ.)
Norman, Donald A. (1988/2002). The Design of Everyday Things. Originally published as The Psychology of Everyday Things. Basic Books: New York.
Gaver, William W. (1992). The Affordances of Media Spaces for Collaboration. Computer Supported Cooperative Work: Proceedings of the 1992 ACM conference on Computer-supported cooperative work. Toronto, Ontario, Canada; 17-24.
- http://portal.acm.org.proxy2.library.uiuc.edu/citation.cfm?id=371596&coll=portal&dl=ACM&CFID=821498&CFTOKEN=24229448
- ISBN:0-89791-542-9
Harrison, Steve; Dourish, Paul (1996). Re-place-ing Space: The roles of place and space in collaborative systems. Computer Supported Cooperative Work: Proceedings of the 1996 ACM conference on Computer supported cooperative work. Boston, Massachusetts, United States; 67-76
- http://portal.acm.org.proxy2.library.uiuc.edu/citation.cfm?id=240193&coll=portal&dl=ACM&CFID=821498&CFTOKEN=24229448
- ISBN:0-89791-765-0
Gaver, William (1996). Affordances for Interaction: The Social is Material for Design. Ecological Psychology. 8(2), 111-129.
Twidale, M.B. (2006). Surveying the Ubicomp Design Space: hill-climbing, fields of dreams, and elephants' graveyards. Workshop on Software Engineering Issues for Ubiquitous Computing, Lancaster, UK, June 2006.
Bower, Matt (2008). Affordance Analysis - Matching Learning Tasks with Learning Technologies. Educational Media International, 45(1), 3-15.
[edit] Informal Example of Affordance Analysis
Here's an example of an informal affordance analysis that Damon Cook (an HCI student in the CS department) did for 590SBD. As he states in a disclaimer he sent me when I asked his permission to post some of his work:
... I didn't do a lot of work to make sure I was doing it exactly right. I feel like I missed a big chunk of the things that could have been done. For example, I didn't talk much about the processes that are used with the things I was comparing and I didn't talk about the social affordances from them, merely the physical affordances. I always thought it was a little weak because of that.
The following analysis came from a brainstorming session he did with a couple of his colleagues:
[edit] Basic Functionality Prototype and Affordance Analysis
Drawing from research about the early design process we did an affordance analysis of the tools currently in use for collaboration in early design versus the technology available for our proposed tool.
[edit] Current Tools
Previous research has shown that designers use several tools to work collaboratively during the early stages of design. These include white boards, sticky notes (often used in conjunction with white boards), paper & pencil, powerpoint slides, descriptive documents (often printed out and brought to meetings), and screenshots or other representations of past designs. Drawing on the reasons that designers gave for choosing to use these tools as well as our own experiences, we created a list of affordances and anti-affordances of each of the tools.
[edit] Whiteboards
Affordances: easily visible, lots of space, simple to use, immediate feedback, common, <--> accessible, quick, cheap, easy to edit/erase, random input devices (your hand and other things besides marker/eraser to interact), easy to zoom/pan (move your body), marker can be used for pointing
Anti-affordances: can't be private, can't make exact duplicates, no "redo" function (loss of history), not portable, no support for comprehension of strokes, easy to smear, static (size, can't move strokes, location), no remote interaction, no computational support
[edit] Paper
(including descriptive documents and representations of past designs)
Affordances: common, inexpensive, lightweight, private, portable, can xerox for extra copies, easy to edit/erase, easy to zoom/pan (move paper), quick, simple to use, immediate feedback, groups are rearrangable/reorderable, pencil can be used for pointing
Anti-affordances: often too small to be easily visible (from distance), no support for comprehension of strokes, static (size, can't move strokes), no remote interaction, no computational support
[edit] Sticky Notes
Affordances: can be easily used in combination with other tools, sticks to things, common, inexpensive, lightweight, private, portable, easy to edit/erase, easy to zoom/pan (move paper), quick, simple to use, immediate feedback, groups are rearrangable/reorderable, often multiple colors can be used to differentiate
Anti-affordances: really small, often too small to be easily visible (from distance), no support for comprehension of strokes, static (size, can't move strokes), no remote interaction, no computational support
[edit] Powerpoint Slides
Affordances: easily interpret information (legible), organized information, good visibility, portable (assuming technology is available), store annotations electronically with file, save and distribute multiple copies, multimedia capability, easily editable (if text or relationships of data), simple interaction, view remotely (which is primary function), good for presenting ideas/information, some computational support (animation)
Anti-affordances: hard to edit or add content (if not built into powerpoint), only one person can edit at a time, bad for interaction, technical issues
[edit] Proposed Computer Tool
To allow us to discover the affordances of our proposed tool, we implemented a prototype that included the most basic functionality that we envision will be necessary for the tool. Experimenting with this prototype gave us an experiential understanding of the affordances provided to supplement our conceptual understanding. With this understanding, as well as information drawn from previous research on why designers choose different computer tools for different tasks, we created a list of affordances and anti-affordances of the technology available for use in our tool.
Affordances: easily visible, lots of space, semi-immediate feedback, easy to edit/erase, private, public, public/private, good for interaction, portable (assuming technology is available), resizable (definitely for small screen and virtually for large display), store annotations electronically with file, save and distribute multiple copies, multimedia capability, easily interpret information (legible), remote interaction, allows for organization of information, potential for multiple input devices, history, redo, can reach everywhere, really easy to clear and start over, layers(add another dimension)
Anti-affordances: network congestion can slow down feedback, complex (might affect mental load of users), upper bound to how fast you can move in the virtual space, expensive, potential speed decrease in drawing, tied to your Tablet (weight, power),technical issues, startup time, not good for short tasks, limited flexibility due to complexity (being able to move around on large screen), hard to tell what privacy mode you're in, less ergonomic
[edit] Social Issues
- Drawing can be for self (figure out idea) or for others (clarify or emphasize a point)
- Easy to accidentally use computer when meaning only to emphasize to people (not computer)
[edit] Informal Review of Selected Literature
Here's some literature I looked at (and sometimes reviewed) when taking Mike Twidale's Scenario Based Design class (590SBD). It addresses some points relevant to the analysis as it is currently used, but is more tangential than anything. I've included it in case anyone is interested. This is hardly an exhaustive list or relevant literature. Both Affordance Analysis and the concept of an Affordance are dealt with in this literature.
[edit] What is an Affordance?
http://www.faculty.virginia.edu/perlab/misc/ReadingMeeting/Jones,2003.pdf
- Jones, Keith S. (2003). What Is an Affordance? ECOLOGICAL PSYCHOLOGY. 15(2), 107–114.
"Theories that address such questions fall into two categories. The first category assumes that objects and events have no inherent meaning, and thus the meaning must be created internally and stored by the animal, that is, an indirect-perception view. The other category assumes that objects and events have inherent meaning, which is detected and exploited by the animal without mental calculation, that is, a direct-perception view."
I think Jones misinterprets Gibson's definition of the term affordance. Jones uses the term to associate meaning with objects and items in the real world to define affordance, but I think that a more appropriate way of looking at it is in terms of function, or potential function, or options, or possibilities.
Note: [from Keith Jones] I believe what I wrote is consistent with your statements about function, options, or possibilities. After all, those possibilities, functions, etc. are uniquely related to the relation between characteristics of the animals and characteristics of the environment.
I think that when computer scientists use the term affordance analysis, the latter meaning is the manner in which they use the term.
Note: [from Keith Jones] I agree, but again I don't think that the two views are incompatible. Instead, the real difference between your viewpoint and my take on Gibson comes about in the next paragraph.
Meaning is a cognitive attribute, and I don't think that it exists outside of cognition--there is no need to personify affordance, I think this personnification simply arose out of his perspective.
Note: [from Keith Jones] This is where your thinking and Gibson's diverge. I don't think I misinterpreted Gibson when I wrote that paper because Gibson was explicitly trying to develop a theory where meaning is external to the person. That is, Gibson would not concur that meaning is ONLY a cognitive thing.
This is important because personification biases our functional thinking, because our brains are constructed to predict behaviors of people/animals/agents in one manner, and behaviors of objects in another.
Question: [from Keith Jones] What evidence do you have for this statement? It sounds like conjecture to me. Relatedly, Gibson would not concur that we perceive inanimate objects in a qualitatively different manner than animate objects. Sure, we tell them apart, but I believe that Gibson would argue that the process of perceiving both of them is the same.
It is such a subtle bias that I think it is better we avoid it, rather than try and figure out how exactly it is affecting our judgement and then take that into account.
Note: [from Keith Jones] Before admonishing people to avoid this subtle bias, I believe that you should provide firm support for such a bias.
"As he discussed later, these thoughts were probably influenced by Gestalt theorists—for example, Koffka (1935), who recognized that the meanings of things seem to be perceived as readily as the things themselves (J. J. Gibson, 1979/1986)."
The problem is that while the Gestalt Psychologists were influential and skilled at pointing out how certain shapes were automatically interpreted with certain meaning associated with them, they absolutely did not consider the meaning to be held within the objects themselves. Indeed, they specialized at using abstractions to evoke meaning (think of the face/wine glass figure/ground visual trick). Instead, they showed that certain perceptions were automatically associated with meaning, even when that meaning was not based in any sort of reality (the figure is ink on bleached paper, after all). In reference to the affordances of paper, there is no meaning in the functional capability of making ink markings on paper with a pen until meaning is associated with the action when it is perceived and processed by a cognition, whether this cognition is conscious or not.
Note: [from Keith Jones] The interesting reader should note that I (as Gibson did) noted that his thinking was influenced by Gestalt Psychologists, but I did not report that his thinking was identical to their thinking. The Gestalt Psychologists provided some impetus for Gibson's theorizing, but he was not a Gestalt Psychologist.
One of Gibson's discussions of the meaning of Affordance quoted in the paper:
"[Objects] can all be said to have properties or qualities: color, texture, composition, size, shape and feature of shape, mass elasticity, rigidity, and mobility. Orthodox psychology asserts that we perceive these objects insofar as we discriminate their properties or qualities. Psychologists carry out elegant experiments in the laboratory to find out how and how well these qualities are discriminated. The psychologists assume that objects are composed of their qualities. But I now suggest that what we perceive when we look at objects are their affordances, not their qualities. We can discriminate the dimensions of difference if required to do so in an experiment, but what the object affords us is what we normally pay attention to. The special combination of qualities into which an object can be analyzed is ordinarily not noticed. (p. 134)"
Another:
"What is meant by an affordance? A definition is in order, especially since the word is not to be found in any dictionary. Subject to revision, I suggest that the affordance of anything is a specific combination of the properties of its substance and its surfaces taken with reference to an animal. The reference may be to an animal in general as distinguished from a plant or to a particular species of animal as distinguished from other species. (p. 67)"
[edit] Cultural Affordances: Space vs. Place
- Harrison, Steve; Dourish, Paul (1996). Re-Place-ing Space: The Roles of Place and Space in Collaborative Systems. Computer Supported Cooperative Work, Proceedings of the 1996 ACM conference on Computer supported cooperative work. Cambridge MA.
"ABSTRACT Many collaborative and communicative environments use notions of “space†and spatial organisation to facilitate and structure interaction. We argue that a focus on spatial models is misplaced. Drawing on understandings from architecture and urban design, as well as from our own research findings, we highlight the critical distinction between “space†and “placeâ€Â. While designers use spatial models to support interaction, we show how it is actually a notion of “place†which fram-es interactive behaviour. This leads us to re-evaluate spatial systems, and discuss how “placeâ€Â, rather than “spaceâ€Â, can support CSCW design."
[edit] Gibson vs. HCI use of the word Affordance
- Bærentsen, Klaus B.; Trettvik, Johan (2002). An activity theory approach to affordance. ACM International Conference Proceeding Series, Proceedings of the second Nordic conference on Human-computer interaction. Århus, Denmark.
Interesting. They reexamine how Gibson used the term, and
argue that it is fundamentally different from how people in
HCI are using it; they propose an alternative approach.
They are not always careful with their distinctions, however:
"It is evident from these citations, that affordances are realized in the interaction between organism and objects in the environment. The concept "affordance" denotes a phenomenon that only exists when organisms are actively living in environments."
Correct. But then the next sentence:
"Affordance is an emergent property of the material world, just like the phenomenon denoted as "water"."
This is not true. We represent certain physical phenomena as "water" in our brain; that is how they are represented in our brains; "water" is a concept/thought component that is manipulable in our conscious/verbal processes. Affordances can be viewed in two lights, related to the space/place distinction in the previous article. One as an objective fact: a pen can be used to leave splotches of ink on paper. One as a mental fact: we know that we can use a pen to write on paper. The importance of Gibson's argument in psychology was that he said:
1) a pen can be used to write on paper, but an active agent is required for this to happen 2) the potential functionality is there whether or not an agent exists to realize that functionality 3) our brains use gestaltesque interpretations of objects that allow us to immediately/subconsciously grasp the potential for the pen to be used to write on paper by us, and that is how our brain interprets the objects as objects, not by their physical characteristics or components--only in use. (We can also use a pen to poke someone's eye out, for instance, but this is not an affordance in Gibson's sense because it is not subconsciously realized, except perhaps if we are really angry)
Gibson, Norman, and the authors of this article Baerentsen & Trettvik, see part (3) as being the reason why the concept of affordance is valuable. But by calling it an emergent property, Baerentsen & Trettvik deny parts (1) and (2) exist as part of the concept of affordance, which is not the case, especially if you look at how Jones uses the concept of affordance in the paper I cited above. That (1) and (2) are important is obvious when you consider the face/wine glass figure ground gestalt picture: You can't drink out of the wine glass despite the gestaltic association of meaning to the figure of the glass. (I could have made this point simply by considering any painting) Similarly, if there is a plexiglass wall between the agent/person and the pen and paper, then there is no true affordance, since the person can't actually use the pen to write on the paper. "water" is a concept. "affordance" is the automatic correct mapping of a functional capability onto objects which is used to create the concept of the object in the mind.
This is even clearer when thinking in terms of activity, especially when you consider learned helplessness--objects surrounding the creature loose their meaning because they loose their affordance because they cannot be accessed.
(Learned Helplessness is best explained through an example/scenario: If you put a rat in a cage and electrify half the floor, the rat will stay on the unelectrified part. If you then electrify the entire floor, eventually the rat will stop trying to escape getting shocked and cower in a corner. If you then turn off the electricity on the part of the floor that was unelectrified before, the rat will never experiment to try and find out if the state of the floor has changed again. It will keep cowering on the electrified portion of the cage. There are other variants on this experiment, such as pushing a lever to unelectrify the cage that stops working temporarily, etc.)
[edit] Semantic and Norm Analysis
Only tangentially relevant, this article seems not to have been published, and hence has not been peer reviewed, so be careful in trusting this article, and do not cite it in a paper.
http://www.soc.staffs.ac.uk/ams1/ICEIS2002.pdf
Salter, Andy; Liu, Kecheng;
What I got out of it:
Semantic Analysis and Norm Analysis is useful in deconstructing ideal versions of systems, or in trying to build an ideal version, but it does not take appropriation into account.
Categories: Research | Research Methods | Methodology | HCI | Design
