TiChi Introduction
GOMS
Fitt's Law
Object-Action Interface
Prescriptive Theories
Fisheye strategy
Conceptual, semantic,
syntactic, & lexical
Direct Manipulation
Information Processing
Hacker's Action Theory
Attention & Memory
Andersen's ACT-R
Knowledge & Mental
Social & Cultural
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Overview
For users to easily learn and interact with computer systems, they must be able to understand the progression and action of each step they take. The theory of direct manipulation describes interactive systems where the user physically interacts with their operating system. The fundamental feature of such a system is user control. Instead of typing commands and allowing the operating system to act as a strange intermediary, a direct manipulation system allows the user to feel like she is in control, by allowing her to physically interact with files and directories, and presenting a visual representation of the progress and end point. Schneiderman [1983] explained the central ideas of user control:
- Visibility of Object and Actions
- Rapid, reversible, incremental actions
- Replacement of complex command-language syntax with direct, visual manipulation of the object of interest.
Scope, Application, and Limitations
Direct manipulation prescribes a general set of rules that have applications across the field of human computer interaction. Because direct manipulation systems present the user with an easy to use, familiar method of interaction, novices particularly have an easier time with these systems[Margono 87]. For experts, well designed systems can be sufficiently fast, though often using keyboard inputs will allow an expert to work faster [Morgan 91]. Thankfully, dual implementation of these systems is generally not that difficult.
Because the system is familiar and easy to use, novices are also likely to learn more quickly. Since direct manipulation shows the progress of steps, errors occur much less often than they do in command type systems. This fact alone gives users confidence to explore and learn more features of the software more quickly. Because of these benefits, direct manipulation is present in designs from word processing to video games.
Example
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The "trash" on the desktop is an excellent example of direct manipulation within computer systems. Users can see both the trash and the files or folders they want to move to the trash. They then physically select the files and drag them to the trash can. While the user is doing this, all of the selected files move as well, illustrating which items the user has selected. When the mouse is placed over the trash, there is a shading indication that it has been selected. The user then has to release the mouse button to move the files to the trash. If there are many files, a dialogue box will show up illustrating the progress of moving files to the trash. Once the action is completed, the files are no longer visible in their original location. The user can change her mind at any time while dragging the files to the trash. Even after placing them there, they can as easily be taken out of the trash and put back in place. Figure 1: Visual progress of moving a folder to the trash |
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Applicability to HCI
Direct manipulation has become the method by which most computer users interact with their machines. Since the introduction of the Mac GUI in List and the early Macintosh machines, and slightly later the Windows interface, users have come to expect a mouse with visual and physical interaction with their operating system and software. Direct manipulation is evident in many other areas as well.
Video games are a prime example. With only a small amount of training, users pick up controllers with buttons and knobs that generally map very well to the way the character is moving in physical space.
The extension into virtual reality is an easy one to make. In these situations, users are surrounded by an environment. In environments like the CAVE at Argonne National Laboratories [Cruz 93], they can literally move around in that physical space, and visualize with normal movements. Since objects are oriented in 3-dimensional space, actions easily map to natural movements. Users can physically reach out, and using the provided hardware, "grab" an object and move it somewhere else.
Other virtual reality systems detect the 3-dimensional movements of the user and adjust accordingly. Remote surgery provides a good example. A surgeon may wear a head set to detect his position and adjust a camera view in the remote site. Gloves detect his exact position and movements, allowing a robotic counterpart on the remote end to replicate his exact movements. In this case, the surgeon is using direct manipulation as a method for controlling the remote system.
References
Cruz-Neira, C. D. j. Sandin, and T. DeFanti, "Surround-screen projection-based virtual reality: The design and implementation of the CAVE", Proceedings of SIGGRAPH Ő93,ACM, New York: 1993. 135-142.
Margono, Sepeedeh and Schneiderman Ben, "A study of file manipulation by novices using commands versus direct manipulation," Twenty-sixth Annual Technical Symposium, ACM, Washington, VD, 1987. 154-159.
Morgan, K, R.L. Morris, and S. Gibbs, "When does a mouse become a rat? orÉComparing performance and preferences in direct manipulation and command line environments," The Computer Journal, 1991: 34 (3). 265-271.
Schneiderman, B. (1983). Direct Manipulation: A step beyond programming languages, IEEE Computer, 16(8), 57-69.
Schneiderman, Ben, Designing the User Interface. Reading, MA: Addison-Wesley: 1998.