Pointing Devices

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Introduction & Rationale

A mouse is a pointing device used to input movement onto a GUI via detecting the shift of X and Y coordinates, as the mouse is moved from one position to another. The mouse was first invented in 1964 by Douglas Engelbart and changed the use of computers from scientists only to consumer friendly. [Inventors.about.com, (n.d.)]. The mouse was chosen as the device as its user friendly with few physical input demonstrated by the fact it is a ubiquitous device found all over the world.

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Ergonomics

Ergonomics, the study of how efficiently an environment can facilitate work is a key part of mouse design. Since, the first pointing devices, such as the ones produced at Xerox Parc, computer device have iteratively been improved to achieve as much ergonomic efficiency as possible.

Figure 1: The Evolution of Mice As you can see computer mice have followed an extensive evolution over their 44 year existence (19682012). Initial designs were extremely square and were only designed to fit a human hand in terms of size not shape. Furthermore, the status quo of computer mice today are designed to include three buttons (one doubles as a scroll wheel) and to fit the a right hand of a human. It is interesting to note how modern designs have foregone the ambidextrous nature of their predecessors as they value the shape of the mouse more than said feature.

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Psychology of Interaction

The computer mouse provides a natural environment in which the user can interact with the computer. Its simple design and smooth, free flowing movement allow the user to use the mouse in an easy and natural way, with little to no concentration needed when carrying out even the most difficult of tasks. 1

Used in much the same way as hands during conversation, the mouse acts as a pointing device to enable users to highlight and select objects of their choice. The mouse draws upon basic sensory mapping and motor skills which are used regularly in day to day life, making computer interaction a more natural experience and relatively easy to learn. According to Zhai and Mackenzie (1998) devices that require use of multiple muscle groups; including those both big and small, are preferred over those requiring the use of just one. This is likely to be due to the similarity of this to everyday life, as very few tasks require the use of only one muscle group. The hand position is also particularly important, with mice allowing the hand to be placed in an open and free manner being preferable over those requiring a locked-in position (Zhai, 2004). This is again likely to be due to its similarity to everyday life, with rigidity and restriction feeling unpleasant and unnatural to the user.

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Description of Controls

Clicking: This is the primary way that users interact with a computer and a mouse itself. There 3 different keys which perform different operations. The leftmost key is used for selection, the rightmost for bringing up contextual options and the middle is used differently depending on the application in question. Scrolling: Scrolling is the newest constant feature across all mouse designs, as until the turn of the century mice where only had moving or clicking capabilities. Scrolling is used navigate up and down a view and is controlled by a wheel in between the left and right buttons. Moving: A mouse is fundamentally a pointing device and in order to point at something a mouse needs to relay movement information to the computer. The mouse has been designed to glide across flat surfaces and these movements correspond to the pointer on screen.

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5.1

Case Study 1: Clicking
Off-line Physiogram

Figure 2: (Dix, 2009)

5.2

On-line Annotated Physiogram

Tapping the button when online has a different effect to holding it down for a certain amount of time. Tapping the left button is normally used for selecting a place on the screen, to click a button for example. Holding it is normally used to select an area, for example a few lines of text, where you press the button at the beginning, and release at the end. Tapping the right button is usually used to bring up a set of options, so you may select a few lines of text with the left button, then right click it to bring up options such as delete, copy and cut.

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6.1

Case Study 2: Scrolling
Off-line Physiogram

6.2

On-line Annotated Physiogram

A computer mouse does not tell the computer its current location, instead it relays the change in location. This is called the ‘Delta’, and it is represented using Cartesian coordinates across a 2D plane (The mouse can move + or - along the Y or X axis). . A stationary mouse conceptually is at its origin position, any change to this is sent to the computer and it is handled appropriately at which point the new current position of the mouse becomes the new origin.

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7.1

Case Study 3: Moving
Off-line Physiogram

7.2

On-line Physiogram

When online, the scroll wheel has multiple functions. When clicked down the scroll bounces back 5

however the mouse changes to a state, typically this is an display scroll state based on mouse movements, the state of the mouse is returned when the scroll is clicked again. The scroll also has n amount of states for scrolling backwards and forwards, the user can keep scrolling forwards and eventually reach the starting point.

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Simultaneous Commands

Of the commands described above, namely: Click, Scroll and Move, each can be activated in tandem with at least another command. 1. Click and Move This action is achieved by depressing the left hand button and moving the mouse to another specific point. In most modern applications this is used to initially select something then plant it in a specific place, thereby inserting that item into that conceptual location. E.g. Dragging a file into the Recycle bin. 2. Others However, whilst it is possible to do the other actions in tandem such as: Scroll & Click or Scroll & Move, they are not catered fro in most modern applications and thus have no result.

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9.1

Limitations of Mice
Desired Use

Mice are designed to be used across an X,Y plane and as a result react unpredictably do rotation, which is a perfectly valid form of movement.

9.2

Handedness

As mentioned within the Ergonomics section, mice today are built to be used by the user’s right hand. This poses a minor but present accessibility and usability problem to those who do not preferably use their right-hand.

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References

1. Inventors.about.com (n.d.) Who Invented the Computer Mouse - Douglas Engelbart. [online] Available at: http://inventors.about.com/library/weekly/aa081898.htm [Accessed: 15 Nov 2012]. 2. Dix, A., Ghazali, M., Gill, S., Hare, J., & Ramduny-Ellis, D. (2009). Physigrams: modelling devices for natural interaction. Formal aspects of computing, 21(6), 613-641. 3. Zhai, S., & MacKenzie, I. S. (1998). Teaching old mice new tricks: Innovations in computer mouse design. Proceedings of Ergon-Axia ’98 - the First World Congress on Ergonomics for Global Quality and Productivity, pp. 80-83 4. Zhai, S. (2004). The Computer Mouse and Related Input Devices.Berkshire Encyclopedia of HumanComputer Interaction, W.S. Bainbridge

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