Lecture 17 — Mental Models | HCI Course | Stanford University

Summary

This video explores the concept of mental models in user interfaces, highlighting how users' perceptions shape their interaction with systems. Using real-world examples like faulty doors and confusing refrigerator dials, it demonstrates how mismatched mental models lead to errors. The video distinguishes between 'slips' (accidental errors) and 'mistakes' (errors due to misunderstanding), offering strategies for designers to improve usability. It also discusses how leveraging familiar metaphors and minimizing discrepancies between real-world practices and technology can enhance user experience, with examples like the Final Scratch DJ system illustrating the power of intuitive design.

Takeaways

• 😀 The learnability of an interface is key to reducing user errors, and understanding user mental models can help in designing better interfaces.
• 😀 Physical-world analogies, like the example of a door with a handle that doesn't open, demonstrate how mismatched expectations can cause errors in user interaction.
• 😀 When designing user interfaces, it's important to align the designer's mental model with the user's mental model to avoid confusion and errors.
• 😀 Misunderstanding the functionality of user interface elements, like refrigerator dials, can lead to mistakes. Clearer designs can prevent these issues.
• 😀 Users often make errors based on their mental models, which are incomplete, inconsistent, and often influenced by superstition or prior experiences.
• 😀 There are two types of errors in user interactions: slips (where the right model is used but the wrong action is performed) and mistakes (where the wrong model is applied, leading to incorrect actions).
• 😀 To prevent slips, improve ergonomics and visual design so that users are less likely to make physical errors, such as pressing the wrong button.
• 😀 Mistakes are prevented by providing better feedback and making it clearer what the user can do, enhancing their understanding of the system's affordances.
• 😀 The infamous 'butterfly ballot' in the 2000 U.S. election exemplifies how poor user interface design can lead to significant errors in decision-making.
• 😀 Consistency in design across systems, like voting interfaces, reduces user errors and promotes familiarity, making the system easier to use for a wider audience.

Q & A

What is the main focus of the video script?

The main focus of the video script is on mental models, particularly in relation to user interfaces, and how different designs can impact the user’s understanding and performance. It discusses how errors occur due to mismatched mental models between users and designers, and how better designs can improve usability.

What is an example of a user interface error discussed in the video?

An example provided in the video is the two-door system at the Stanford computer science building. Both doors have the same handle, but one door is always locked, leading to confusion and frequent errors by users who expect both doors to open.

What mental model issue is presented by the refrigerator example?

The refrigerator example shows a misunderstanding of the dials controlling the cooling system. Users might assume each dial controls a separate unit (fridge and freezer), but in reality, the system only has one cooling unit, and both dials must be adjusted together to change the freezer’s temperature.

What is the difference between a 'slip' and a 'mistake' in user behavior?

A slip occurs when a user has the correct mental model but makes a physical or motor error, like pressing the wrong button. A mistake happens when a user has the wrong mental model, like taking the wrong exit while driving because they believe it's the correct route.

How can designers prevent slips in user interfaces?

Designers can prevent slips by improving the ergonomics and visual design of the interface, such as making buttons larger, spreading options apart, and making targets easier to hit.

How can designers reduce mistakes in user interfaces?

Mistakes can be reduced by providing better feedback and clearer options for users, improving their ability to understand what is possible and what the interface is doing.

What was the issue with the Palm Beach County voting ballot during the 2000 U.S. presidential election?

The issue was the confusing design of the butterfly ballot, where the hole corresponding to Al Gore’s name was misaligned with the arrow, causing some voters to mistakenly vote for Pat Buchanan instead.

What is the importance of consistency in user interface design, as demonstrated by the butterfly ballot example?

Consistency is crucial because it helps users develop accurate mental models. If every county designs its own voting system, inconsistencies are more likely, leading to user errors. A standardized system reduces these risks.

What is the proposed solution for electronic voting to ensure vote accuracy?

The solution is to have the machine print a paper receipt of the vote, which is stored behind a transparent pane. Voters can verify their vote in real-time, ensuring that the machine recorded it correctly, without the risk of vote buying.

What is an example of a user interface that successfully balances new functionality with traditional design?

The Final Scratch system for DJs is an example. It uses vinyl records with a code to control a digital music system, allowing DJs to maintain the familiar tactile interaction of vinyl records while leveraging digital functionality for greater flexibility and portability.