CS474: Human Computer Interaction - The Way We Interact - Affordances and Signifiers
Activity Goals
The goals of this activity are:- To differentiate signifiers and affordances
- To identify signifiers in everyday life
- To identify potential shortcomings in both signifiers and affordances in technology
Supplemental Reading
Feel free to visit these resources for supplemental background reading material.- 50 Years Later, We Still Don't Grasp the Mother of All Demos
- Augmenting Human Intellect
- Haubursin, C. - It’s not you. Phones are designed to be addicting.
- Bush, V. - As We May Think
- Schalk, Z. - Humans in Control - Thoughts on the Past, Present, and Future of HCI
- What are Affordances?
- What are Signifiers?
The Activity
Directions
Consider the activity models and answer the questions provided. First reflect on these questions on your own briefly, before discussing and comparing your thoughts with your group. Appoint one member of your group to discuss your findings with the class, and the rest of the group should help that member prepare their response. Answer each question individually from the activity, and compare with your group to prepare for our whole-class discussion. After class, think about the questions in the reflective prompt and respond to those individually in your notebook. Report out on areas of disagreement or items for which you and your group identified alternative approaches. Write down and report out questions you encountered along the way for group discussion.Model 1: As We May Think
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Questions
- Vannevar Bush published As We May Think in 1945. What was the temporal context of this article? What was the state of technology?
- What are some fields whose body of knowledge is so great that one person cannot possibly hold all of it?
- What are some ways in which we organize our expanding collective knowledge?
Model 2: The Mother of All Demos
Questions
- The Mother of All Demos represented a shift from mainframe computing to personal computing directly at the terminal. What were some technologies demonstrated at the Mother of All Demos?
- Was the Mother of All Demos really about technologies? What was the central thesis of the presentation?
Model 3: Human Behavior
Questions
- What are some ways in which you feel compelled to use, or to continue to use, your smartphone or portable device?
Model 4: Affordances and Signifiers
Questions
- What are examples of visual signifiers in the physical world?
- What are some intuitive or universal signifiers in technology?
- Are some affordances made clear without signifiers? What and how? For example, how might a Norman Door be remedied without requiring signed instructions?
- Consider a walk/don't walk sign at a crosswalk. What non-visual signifiers would better indicate instructions to visually impaired persons?
- What are some examples of affordances that exist for some people but not for others? How can these be improved?
- In the original Super Mario Bros., how does World 1-1 serve as a tutorial for new players without requiring textual instructions?
Try It: Fitts’s Law — Predicting How Fast We Can Point
Affordances invite an action; Fitts’s law predicts how fast that action can physically be performed. This notebook simulates a classic pointing experiment, fits the law with a linear regression, and then uses the fitted model to compare real design choices (bigger buttons vs. closer buttons vs. screen-edge targets). It’s one of the few quantitative laws in HCI, and you can reproduce its core analysis in about twenty lines of Python.
Click the badge to run the notebook in your browser with Google Colab (no installation required), or download the notebook to run it locally with Jupyter.
Explore Further
- Laws of UX - Fitts’s Law — a one-page visual summary of the law and its design takeaways (make targets big, put them where the pointer already is).
- Fitts, P. M. (1954) - The Information Capacity of the Human Motor System — the original paper: human movement framed as an information channel, an idea borrowed directly from Shannon.
- Interaction Design Foundation - Fitts’s Law: The Importance of Size and Distance in UI Design — a beginner-friendly written walkthrough with annotated interface examples.