06-04 · Week 6
Prototypes: lo-fi, hi-fi, Wizard of Oz and compromises
Low and high fidelity prototypes, paper prototyping, faking interaction with Wizard of Oz and video, and the horizontal versus vertical compromise.
- Define a prototype and contrast lo-fi with hi-fi.
- List the advantages and practical issues of paper prototypes.
- Explain Wizard of Oz and video prototypes and when each is used.
- Distinguish horizontal from vertical prototypes.
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Intuition
A prototype exists to answer a question quickly. If it costs more than the answer is worth, it is the wrong prototype.
A prototype is something stakeholders can interact with, at low or high fidelity
The lecture defines a prototype as one manifestation of a design that allows stakeholders to interact with it. In other design fields it is a small-scale model, such as a miniature car or building. In interaction design it may be paper or cardboard, or a sophisticated software package. There are two types, low fidelity and high fidelity.
Compare
Lo-fi
Hi-fi
Paper prototypes keep the focus on ideas
Paper prototypes use 3 x 5 inch index cards or printable sketch sheet templates (the lecture cites sketchsheets.com), with each card representing one element of interaction. In evaluation you step through the cards. Sticky notes can stand for parts of the screen that users move around.
Exam detail
Advantages: non-technical people can interact easily with the design team; produced quickly so the focus is on ideas, not details; flexible, parts adjust so it can be quickly redesigned.
Practical issues: if many people handle it, it must survive; the amount of detail depends on the purpose of the evaluation, but must be enough for someone to use it without help.
Faking interaction: Wizard of Oz and video
How a prototype is implemented is limited only by imagination, time and the materials to hand. The lecture names two ways of faking interaction. In Wizard of Oz, the user thinks they are interacting with a computer, but a human is responding. It simulates interaction during testing. The lecture cites voice-assistant and robo-taxi studies, and kiosk demos. A video prototype is a communication tool for explaining how a prototype is used in real life. Early on, you fake interaction by manually swapping paper wireframes on a phone or laptop. Later, it shows what the product looks like and can do.
To make one: create a storyboard (task, motivation of use, user behaviour), record an actor using the model as if fully functional, and edit out the faking or keep only the needed frames. You need a camera (a phone will do), actors (teammates, family, friends), a realistic setting, a mock-up model and editing software. Record first and edit later.
Every prototype is a compromise
The idea of a prototype is to produce something quickly to test one aspect. The best prototype makes the possibilities and limitations of a design idea visible and measurable in the simplest and most efficient way. Two common compromises (Hartson and Pyla, 2019): horizontal, a wide range of functions with little detail, and vertical, a lot of detail for only a few functions.
Pitfall
Wizard of Oz and video prototypes are not fidelity levels. They are techniques for faking interaction. Horizontal and vertical describe breadth versus depth, not lo-fi versus hi-fi, though the lecture’s summary lists both as separate trade-offs.
Recall
Which compromise gives many functions with little detail, and which gives few functions in depth?
Horizontal gives many functions with little detail; vertical gives a lot of detail for a few functions.
Check yourself
Source
Lecture 6 PDF