Publication statistics

Pub. period:1989-2011
Pub. count:67
Number of co-authors:61



Co-authors

Number of publications with 3 favourite co-authors:

R. William Soukoreff:9
Bill Buxton:6
Shawn X. Zhang:5

 

 

Productive colleagues

I. Scott MacKenzie's 3 most productive colleagues in number of publications:

Ravin Balakrishnan:108
Abigail Sellen:81
Bill Buxton:78
 
 
 

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I. Scott MacKenzie

Ph.D

Picture of I. Scott MacKenzie.
Update pic
Has also published under the name of:
"Ian Scott MacKenzie"

Personal Homepage:
http://www.yorku.ca/mack/

Current place of employment:
York University

Scott MacKenzie is Associate Professor at York University, Canada. His research area includes human-computer interaction with an emphasis on human performance measurement and modeling, experimental methods and evaluation, interaction devices and techniques, alphanumeric entry, language modeling, and mobile computing. He recieved Ph.D in 1992 at the University of Toronto He has more than 100 peer-reviewed publications in the field of Human-Computer Interaction (including more than 30 from the ACM's annual SIGCHI conference) and has given numerous invited talks over the past 20 years. Since 1999, he has been Associate Professor of Computer Science and Engineering at York University, Canada.

 

Publications by I. Scott MacKenzie (bibliography)

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2011
 
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Sporka, Adam J., Felzer, Torsten, Kurniawan, Sri H., Polc;ek, A Ondr;ej, Haiduk, Paul and MacKenzie, I. Scott (2011): CHANTI: predictive text entry using non-verbal vocal input. In: Proceedings of ACM CHI 2011 Conference on Human Factors in Computing Systems 2011. pp. 2463-2472. Available online

This paper introduces a text entry application for users with physical disabilities who cannot utilize a manual keyboard. The system allows the user to enter text hands-free, with the help of "Non-verbal Vocal Input" (e.g., humming or whistling). To keep the number of input sounds small, an ambiguous keyboard is used. As the user makes a sequence of sounds, each representing a subset of the alphabet, the program searches for matches in a dictionary. As a model for the system, the scanning-based application QANTI was redesigned and adapted to accept the alternative input signals. The usability of the software was investigated in an international longitudinal study done at locations in the Czech Republic, Germany, and the United States. Eight test users were recruited from the target community. The users differed in the level of speech impairment. Three users did not complete the study due to the severity of their impairment. By the end of the experiment, the users were able to enter text at rates between 10 and 15 characters per minute.

© All rights reserved Sporka et al. and/or their publisher

 
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Castellucci, Steven J. and MacKenzie, I. Scott (2011): Gathering text entry metrics on android devices. In: Proceedings of ACM CHI 2011 Conference on Human Factors in Computing Systems 2011. pp. 1507-1512. Available online

We developed an application to gather text entry speed and accuracy metrics on Android devices. This paper details the features of the application and describes a pilot study to demonstrate its utility. We evaluated and compared three mobile text entry methods: QWERTY typing, handwriting recognition, and shape writing recognition. Handwriting was the slowest and least accurate technique. QWERTY was faster than shape writing, but we found no significant difference in accuracy between the two techniques.

© All rights reserved Castellucci and MacKenzie and/or their publisher

 
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MacKenzie, I. Scott, Soukoreff, R. William and Helga, Joanna (2011): 1 thumb, 4 buttons, 20 words per minute: design and evaluation of H4-writer. In: Proceedings of the 2011 ACM Symposium on User Interface Software and Technology 2011. pp. 471-480. Available online

We present what we believe is the most efficient and quickest four-key text entry method available. H4-Writer uses Huffman coding to assign minimized key sequences to letters, with full access to error correction, punctuation, digits, modes, etc. The key sequences are learned quickly, and support eyes-free entry. With KSPC = 2.321, the effort to enter text is comparable to multitap on a mobile phone keypad; yet multitap requires nine keys. In a longitudinal study with six participants, an average text entry speed of 20.4

© All rights reserved MacKenzie et al. and/or ACM Press

2010
 
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Tinwala, Hussain and MacKenzie, I. Scott (2010): Eyes-free text entry with error correction on touchscreen mobile devices. In: Proceedings of the Sixth Nordic Conference on Human-Computer Interaction 2010. pp. 511-520. Available online

We present an eyes-free text entry method for mobile touchscreen devices. Input progresses by inking Graffiti strokes using a finger on a touchscreen. The system includes a word-level error correction algorithm. Auditory and tactile feedback guide eyes-free entry using speech and non-speech sounds, and by vibrations. In a study with 12 participants, three different feedback modes were tested. Entry speed, accuracy, and algorithm performance were compared between the three feedback modes. An overall entry speed of 10.0 wpm was found with a maximum rate of 21.5 wpm using a feedback mode that required a recognized stroke at the beginning of each word. Text was entered with an

© All rights reserved Tinwala and MacKenzie and/or their publisher

 
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MacKenzie, I. Scott and Felzer, Torsten (2010): SAK: Scanning ambiguous keyboard for efficient one-key text entry. In ACM Transactions on Computer-Human Interaction, 17 (3) p. 11. Available online

The design and evaluation of a scanning ambiguous keyboard (SAK) is presented. SAK combines the most demanding requirement of a scanning keyboard -- input using one key or switch -- with the most appealing feature of an ambiguous keyboard -- one key press per letter. The optimal design requires just 1.713 scan steps per character for English text entry. In a provisional evaluation, 12 able-bodied participants each entered 5 blocks of text with the scanning interval decreasing from 1100 ms initially to 700 ms at the end. The average text entry rate in the 5th block was 5.11 wpm with 99% accuracy. One participant performed an additional five blocks of trials and reached an average speed of 9.28 wpm on the 10th block. Afterwards, the usefulness of the approach for persons with severe physical disabilities was shown in a case study with a software implementation of the idea explicitly adapted for that target community.

© All rights reserved MacKenzie and Felzer and/or ACM Press

2009
 
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MacKenzie, I. Scott (2009): Citedness, uncitedness, and the murky world between. In: Proceedings of ACM CHI 2009 Conference on Human Factors in Computing Systems 2009. pp. 2545-2554. Available online

We test a recent claim in an opinion piece (interactions, May/June 2008, pp. 45-47) that publications by HCI researchers have little or no impact. The alleged "phenomenon of uncitedness" was not supported. An examination of all 443 papers in the CHI Proceedings (1991-1995), ACM TOCHI (1994-1999), and Human-Computer Interaction (1991-1995) found an average of 93.8, 106.7, and 80.4 citations per paper, respectively. H-index as an impact measure is explained, with values given for members of the CHI Academy. The mean of 34.3 suggests that the group, taken as a whole, have had a significant impact on human-computer interaction.

© All rights reserved MacKenzie and/or ACM Press

 
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Sasangohar, Farzan, MacKenzie, I. Scott and Scott, Stacey D. (2009): Evaluation of Mouse and Touch Input for a Tabletop Display Using Fitts' Reciprocal Tapping Task. In: Proceedings of the Human Factors and Ergonomics Society 53rd Annual Meeting 2009. pp. 839-843. Available online

User performance with a tabletop display was tested using touch-based and mouse-based interaction in a traditional pointing task. Dependent variables were throughput, error rate, and movement time. In a study with 12 participants, touch had a higher throughput with average of 5.53 bps compared to 3.83 bps for the mouse. Touch also had a lower movement time on average, with block means ranging from 403 ms to 1051 ms vs. 607 ms to 1323 ms with the

© All rights reserved Sasangohar et al. and/or their publisher

 
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MacKenzie, I. Scott (2009): The one-key challenge: searching for a fast one-key text entry method. In: Eleventh Annual ACM SIGACCESS Conference on Assistive Technologies 2009. pp. 91-98. Available online

A new one-key text entry method is presented. SAK, for "scanning ambiguous keyboard", combines one-key physical input (including error correction) with three virtual letter keys and a SPACE key. The virtual letter keys are highlighted in sequence ("scanned") and selected when the key bearing the desired letter receives focus. There is only one selection per letter. Selecting SPACE transfers scanning to a word-selection region, which presents a list of candidate words. A novel feature of SAK is multiple-letter-selection in a single scanning interval. In an evaluation with 12 participants, average entry speeds reached 5.11 wpm (all trials, 99% accuracy) or 7.03 wpm (error-free trials). A modification using "timer restart on selection" allowed for more time and more selections per scanning interval. One participant performed extended trials (5 blocks x 5 phrases/block) with the modification and reached an average entry speed of 9.28 wpm.

© All rights reserved MacKenzie and/or his/her publisher

 
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Natapov, Daniel, Castellucci, Steven J. and MacKenzie, I. Scott (2009): ISO 9241-9 evaluation of video game controllers. In: Proceedings of the 2009 Conference on Graphics Interface 2009. pp. 223-230. Available online

Fifteen participants completed a study comparing video game controllers for point-select tasks. We used a Fitts' law task, as per ISO 9241-9, using the Nintendo Wii Remote for infrared pointing, the Nintendo Classic Controller for analogue stick pointing, and a standard mouse as a baseline condition. The mouse had the highest throughput at 3.78 bps. Both game controllers performed poorly by comparison. The Wii Remote throughput was 31.5% lower, at 2.59 bps, and the Classic Controller 60.8% lower at 1.48 bps. Comparing just the video game controllers, the Wii Remote presents a 75% increase in throughput over the Classic Controller. Error rates for the mouse, Classic Controller, and the Wii

© All rights reserved Natapov et al. and/or their publisher

 
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Teather, Robert J., Pavlovych, Andriy, Stuerzlinger, Wolfgang and MacKenzie, I. Scott (2009): Effects of tracking technology, latency, and spatial jitter on object movement. In: Proceedings of the 2009 IEEE Symposium on 3D User Interfaces 2009. pp. 43-50.

 Cited in the following chapter:

3D User Interfaces: [/encyclopedia/3d_user_interfaces.html]


 
 Cited in the following chapter:

3D User Interfaces: [/encyclopedia/3d_user_interfaces.html]


 
2008
 
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Castellucci, Steven J. and MacKenzie, I. Scott (2008): Graffiti vs. unistrokes: an empirical comparison. In: Proceedings of ACM CHI 2008 Conference on Human Factors in Computing Systems April 5-10, 2008. pp. 305-308. Available online

Unistrokes and Graffiti are stylus-based text entry techniques. While Unistrokes is recognized in academia, Graffiti is commercially prevalent in PDAs. Though numerous studies have investigated the usability of Graffiti, none exists to compare its long-term performance with that of Unistrokes. This paper presents a longitudinal study comparing entry speed, correction rate, stroke duration, and preparation (i.e., inter-stroke) time of these two techniques. Over twenty fifteen-phrase sessions, performance increased from 4.0 wpm to 11.4 wpm for Graffiti and from 4.1 wpm to 15.8 wpm for Unistrokes. Correction rates were high for both techniques. However, rates for Graffiti remained relatively

© All rights reserved Castellucci and MacKenzie and/or ACM Press

 
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Wobbrock, Jacob O., Cutrell, Edward, Harada, Susumu and MacKenzie, I. Scott (2008): An error model for pointing based on Fitts' law. In: Proceedings of ACM CHI 2008 Conference on Human Factors in Computing Systems April 5-10, 2008. pp. 1613-1622. Available online

For decades, Fitts' law (1954) has been used to model pointing time in user interfaces. As with any rapid motor act, faster pointing movements result in increased errors. But although prior work has examined accuracy as the "spread of hits," no work has formulated a predictive model for error rates (0-100%) based on Fitts' law parameters. We show that Fitts' law mathematically implies a predictive error rate model, which we derive. We then describe an experiment in which target size, target distance, and movement time are manipulated. Our results show a strong model fit: a regression analysis of observed vs. predicted error rates yields a correlation of R{sup:2}=.959 for N=90 points. Furthermore, we show that the effect on error rate of target size (W) is greater than that of target distance (A), indicating a departure from Fitts' law, which maintains that W and A contribute proportionally to index of difficulty (ID). Our error model can be used with Fitts' law to estimate and predict error rates along with speeds, providing a framework for unifying this dichotomy.

© All rights reserved Wobbrock et al. and/or ACM Press

 
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MacKenzie, I. Scott and Isokoski, Poika (2008): Fitts' throughput and the speed-accuracy tradeoff. In: Proceedings of ACM CHI 2008 Conference on Human Factors in Computing Systems April 5-10, 2008. pp. 1633-1636. Available online

We describe an experiment to test the hypothesis that Fitts' throughput is independent of the speed-accuracy tradeoff. Eighteen participants used a mouse in performing a total of 5,400 target selection trials. Comparing nominal, speed-emphasis, and accuracy-emphasis conditions, significant main effects were found on movement time (ms) and error rate (%), but not on throughput (bits/s). In the latter case, failure to reject the null hypothesis of "no significant difference" (i.e., .05 < p < 1) is viewed as evidence supporting the constant-throughput hypothesis.

© All rights reserved MacKenzie and Isokoski and/or ACM Press

 
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Tinwala, Hussain and MacKenzie, I. Scott (2008): Letterscroll: text entry using a wheel for visually impaired users. In: Proceedings of ACM CHI 2008 Conference on Human Factors in Computing Systems April 5-10, 2008. pp. 3153-3158. Available online

Four text entry techniques for visually impaired users are presented. LetterScroll uses a mouse wheel to maneuver a cursor across a sequence of characters, and a button for character selection. Keystrokes per character (KSPC) vary from 6.97 to 2.68. After extensive analyses and pilot testing, two variations were chosen for initial evaluation. Method 1 (M1) uses the mouse alone to enter text. Method 4 (M4) also uses the keyboard to access vowels. In a study with seven blindfolded participants, entry rates averaged 2.9 wpm for M1 and 4.4 wpm for M4. Error rates for both methods were about 3.4%.

© All rights reserved Tinwala and MacKenzie and/or ACM Press

 
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Castellucci, Steven J. and MacKenzie, I. Scott (2008): Unigest: text entry using three degrees of motion. In: Proceedings of ACM CHI 2008 Conference on Human Factors in Computing Systems April 5-10, 2008. pp. 3549-3554. Available online

This paper introduces UniGest, a technique that provides pointer input and text entry in a single device without occupying the display. It uses a Nintendo Wii motion-sensing remote to capture gestures that are mapped to character input. A gesture alphabet is proposed, with each gesture composed of at most two primitive motions. A web-based user study measured movement times for primitive motions. Results range from 296 to 481 ms, implying an upper-bound UniGest text entry performance prediction of 27.9 wpm.

© All rights reserved Castellucci and MacKenzie and/or ACM Press

 
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Fazl-Ersi, Ehsan, MacKenzie, I. Scott and Tsotsos, John K. (2008): sLab: smart labeling of family photos through an interactive interface. In: JCDL08 Proceedings of the 8th ACM/IEEE-CS Joint Conference on Digital Libraries 2008. pp. 351-354. Available online

A novel technique for semi-automatic photo annotation is proposed and evaluated. The technique, sLab, uses face processing algorithms and a simplified user interface for labeling family photos. A user study compared our system with two others. One was Adobe Photoshop Element. The other was an in-house implementation of a face clustering interface recently proposed in the research community. Nine participants performed an annotation task with each system on faces extracted from a set of 150 images from their own family photo albums. As the faces were all well known to participants, accuracy was near perfect with all three systems. On annotation time, sLab was 25% faster than Photoshop Element and 16% faster than the face clustering interface.

© All rights reserved Fazl-Ersi et al. and/or ACM Press

 
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MacKenzie, I. Scott and Zhang, Xuang (2008): Eye typing using word and letter prediction and a fixation algorithm. In: Rih, Kari-Jouko and Duchowski, Andrew T. (eds.) ETRA 2008 - Proceedings of the Eye Tracking Research and Application Symposium March 26-28, 2008, Savannah, Georgia, USA. pp. 55-58. Available online

 
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Gong, Jun, Tarasewich, Peter and MacKenzie, I. Scott (2008): Improved word list ordering for text entry on ambiguous keypads. In: Proceedings of the Fifth Nordic Conference on Human-Computer Interaction 2008. pp. 152-161. Available online

We present a design methodology for small ambiguous keypads, where input often produces a list of candidate words for a given desired word. The methodology uses context through semantic relatedness and a part-of-speech language model to improve the order of candidate words and, thus, reduce the overall number of keystrokes per character entered. Simulations yield improvements in text entry speed of about 10% and reductions in errors of about

© All rights reserved Gong et al. and/or their publisher

2007
 
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Zhang, Xuan and MacKenzie, I. Scott (2007): Evaluating Eye Tracking with ISO 9241 - Part 9. In: Jacko, Julie A. (ed.) HCI International 2007 - 12th International Conference - Part III 2007. pp. 779-788. Available online

2006
 
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MacKenzie, I. Scott, Chen, Javier and Oniszczak, Aleks (2006): Unipad: single stroke text entry with language-based acceleration. In: Proceedings of the Fourth Nordic Conference on Human-Computer Interaction 2006. pp. 78-85. Available online

A stylus-based text entry technique called Unipad is presented. Unipad combines single-stroke text input with language-based acceleration techniques, including word completion, suffix completion, and frequent word prompting. In a study with ten participants, entry rates averaged 11.6 wpm with 0.90% errors after two hours of practice. In follow-on sessions to establish the expert potential, four users entered "the quick brown fox" phrase repeatedly for four blocks of 15 minutes each. Average rates on the last block ranged from 17.1 to 35.1 wpm, with peak rates reaching 48 wpm.

© All rights reserved MacKenzie et al. and/or ACM Press

 
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Klochek, Chris and MacKenzie, I. Scott (2006): Performance measures of game controllers in a three-dimensional environment. In: Proceedings of the 2006 Conference on Graphics Interface 2006. pp. 73-79. Available online

Little work exists on the testing and evaluation of computer-game related input devices. This paper presents five new performance metrics and utilizes two tasks from the literature to quantify differences between input devices in constrained three-dimensional environments, similar to "first-person"-genre games. The metrics are Mean Speed Variance, Mean Acceleration Variance, Percent View Moving, Target Leading Analysis, and Mean Time-to-Reacquire. All measures are continuous, as they evaluate movement during a trial. The tasks involved tracking a moving target for several seconds, with and without target acceleration. An evaluation between an X-Box gamepad and a standard PC mouse demonstrated the ability of the metrics to help reveal and explain performance differences between the devices.

© All rights reserved Klochek and MacKenzie and/or Canadian Information Processing Society

 
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Majaranta, Pivi, MacKenzie, I. Scott, Aula, Anne and Rih, Kari-Jouko (2006): Effects of feedback and dwell time on eye typing speed and accuracy. In Universal Access in the Information Society, 5 (2) pp. 199-208. Available online

Eye typing provides a means of communication that is especially useful for people with disabilities. However, most related research addresses technical issues in eye typing systems, and largely ignores design issues. This paper reports experiments studying the impact of auditory and visual feedback on user performance and experience. Results show that feedback impacts typing speed, accuracy, gaze behavior, and subjective experience. Also, the feedback should be matched with the dwell time. Short dwell times require simplified feedback to support the typing rhythm, whereas long dwell times allow extra information on the eye typing process. Both short and long dwell times benefit from combined visual and auditory feedback. Six guidelines for designing feedback for gaze-based text entry are provided.

© All rights reserved Majaranta et al. and/or Springer Verlag

 
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Miniotas, Darius, Spakov, Oleg, Tugoy, Ivan and MacKenzie, I. Scott (2006): Speech-augmented eye gaze interaction with small closely spaced targets. In: Rih, Kari-Jouko and Duchowski, Andrew T. (eds.) ETRA 2006 - Proceedings of the Eye Tracking Research and Application Symposium March 27-29, 2006, San Diego, California, USA. pp. 67-72. Available online

2005
 
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Kulikov, Sergey, MacKenzie, I. Scott and Stuerzlinger, Wolfgang (2005): Measuring the effective parameters of steering motions. In: Proceedings of ACM CHI 2005 Conference on Human Factors in Computing Systems 2005. pp. 1569-1572. Available online

The steering law model describes pointing device motion through constrained paths. Previous uses of the model are deficient because they are built using only error-free responses, ignoring altogether the path of the cursor. We correct this by proposing and validating a technique to include spatial variability, including errors. The technique is a variant of the well-known "effective target width" used in Fitts' law models. An experiment designed to test our technique demonstrates the improvement: Correlations are consistently higher when spatial variability is included in building the model. Suggestions to aid further development of the steering law model are included.

© All rights reserved Kulikov et al. and/or ACM Press

2004
 
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Oniszczak, Aleks and MacKenzie, I. Scott (2004): A comparison of two input methods for keypads on mobile devices. In: Proceedings of the Third Nordic Conference on Human-Computer Interaction October 23-27, 2004, Tampere, Finland. pp. 101-104. Available online

Two mobile device text entry methods were evaluated. The well-known Multitap method was compared to our RollPad method on a new device utilizing a tactile touchpad in place of a keypad. RollPad was well liked by participants. KSPC (keystrokes per character) was significantly lower: 1.42 compared to 2.13 with Multitap. However, no significant difference was found in error rates or entry speed, with speed measured at about 7.3 wpm for both methods.

© All rights reserved Oniszczak and MacKenzie and/or ACM Press

 
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Soukoreff, R. William and MacKenzie, I. Scott (2004): Towards a standard for pointing device evaluation, perspectives on 27 years of Fitts' law research in HCI. In International Journal of Human-Computer Studies, 61 (6) pp. 751-789. Available online

This paper makes seven recommendations to HCI researchers wishing to construct Fitts' law models for either movement time prediction, or for the comparison of conditions in an experiment. These seven recommendations support (and in some cases supplement) the methods described in the recent ISO 9241-9 standard on the evaluation of pointing devices. In addition to improving the robustness of Fitts' law models, these recommendations (if widely employed) will improve the comparability and consistency of forthcoming publications. Arguments to support these recommendations are presented, as are concise reviews of 24 published Fitts' law models of the mouse, and 9 studies that used the new ISO standard.

© All rights reserved Soukoreff and MacKenzie and/or Academic Press

2003
 
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MacKenzie, I. Scott (2003): Motor Behavior Models for Human-Computer Interaction. In: Carroll, John M. (ed.). "HCI Models, Theories, and Frameworks". San Francisco: Morgan Kaufman Publisherspp. 27-53

 
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Soukoreff, R. William and MacKenzie, I. Scott (2003): Metrics for text entry research: an evaluation of MSD and KSPC, and a new unified error metric. In: Cockton, Gilbert and Korhonen, Panu (eds.) Proceedings of the ACM CHI 2003 Human Factors in Computing Systems Conference April 5-10, 2003, Ft. Lauderdale, Florida, USA. pp. 113-120.

 
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Soukoreff, R. William and MacKenzie, I. Scott (2003): Input-Based Language Modelling in the Design of High Performance Text Input Techniques. In: Graphics Interface 2003 June 11-13, 2003, Halifax, Nova Scotia, Canada. pp. 89-96.

2002
 
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MacKenzie, I. Scott (2002): Introduction to This Special Issue on Text Entry for Mobile Computing. In Human-Computer Interaction, 17 (2) pp. 141-145. Available online

 
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MacKenzie, I. Scott and Soukoreff, R. William (2002): Text Entry for Mobile Computing: Models and Methods, Theory and Practice. In Human-Computer Interaction, 17 (2) pp. 147-198.

Text input for mobile or handheld devices is a flourishing research area. This article begins with a brief history of the emergence and impact of mobile computers and mobile communications devices. Key factors in conducting sound evaluations of new technologies for mobile text entry are presented, including methodology and experiment design. Important factors to consider are identified and elaborated, such as focus of attention, text creation versus text copy tasks, novice versus expert performance, quantitative versus qualitative measures, and the speed-accuracy trade-off. An exciting area within mobile text entry is the combined use of Fitts' law and a language corpus to model, and subsequently optimize, a text entry technique. The model is described, along with examples for a variety of soft keyboards as well as the telephone keypad. A survey of mobile text entry techniques, both in research papers and in commercial products, is presented.

© All rights reserved MacKenzie and Soukoreff and/or Taylor and Francis

 
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MacKenzie, I. Scott and Soukoreff, R. William (2002): A Model of Two-Thumb Text Entry. In: Graphics Interface 2002 May 27-29, 2002, Calgary, Alberta, Canada. pp. 117-124.

 
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MacKenzie, I. Scott and Soukoreff, R. William (2002): A character-level error analysis technique for evaluating text entry methods. In: Proceedings of the Second Nordic Conference on Human-Computer Interaction October 19-23, 2002, Aarhus, Denmark. pp. 243-246. Available online

We describe a technique to analyse character-level errors in evaluations of text entry methods. Using an algorithm for sequence comparisons, we generate the set of optimal alignments between the presented and transcribed text. Percharacter errors, categorized as insertions, substitutions, or deletions, are obtained by analysing the alignments and applying a weighting factor. A detailed example using a real data set is given.

© All rights reserved MacKenzie and Soukoreff and/or ACM Press

 
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MacKenzie, I. Scott (2002): KSPC (Keystrokes per Character) as a Characteristic of Text Entry Techniques. In: Paterno, Fabio (ed.) Mobile Human-Computer Interaction - 4th International Symposium - Mobile HCI 2002 September 18-20, 2002, Pisa, Italy. pp. 195-210. Available online

2001
 
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MacKenzie, I. Scott, Kauppinen, Tatu and Silfverberg, Miika (2001): Accuracy Measures for Evaluating Computer Pointing Devices. In: Beaudouin-Lafon, Michel and Jacob, Robert J. K. (eds.) Proceedings of the ACM CHI 2001 Human Factors in Computing Systems Conference March 31 - April 5, 2001, Seattle, Washington, USA. pp. 9-16. Available online

In view of the difficulties in evaluating computer pointing devices across different tasks within dynamic and complex systems, new performance measures are needed. This paper proposes seven new accuracy measures to elicit (sometimes subtle) differences among devices in precision pointing tasks. The measures are target re-entry, task axis crossing, movement direction change, orthogonal direction change, movement variability, movement error, and movement offset. Unlike movement time, error rate, and throughput, which are based on a single measurement per trial, the new measures capture aspects of movement behaviour during a trial. The theoretical basis and computational techniques for the measures are described, with examples given. An evaluation with four pointing devices was conducted to validate the measures. A causal relationship to pointing device efficiency (viz. throughput) was found, as was an ability to discriminate among devices in situations where differences did not otherwise appear. Implications for pointing device research are discussed.

© All rights reserved MacKenzie et al. and/or ACM Press

 
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MacKenzie, I. Scott and Zhang, Shawn X. (2001): An empirical investigation of the novice experience with soft keyboards. In Behaviour and Information Technology, 20 (6) pp. 411-418.

An experiment with 12 participants tested text entry rates on two sizes of soft keyboards with either a Qwerty layout or a layout presenting a randomized letter arrangement after each tap. The randomized layout simulated the novice experience by requiring users to visually scan the layout for each tap to find the intended letter. Rates for the Qwerty layouts were about 20 wpm with no significant difference between the large and small size. Rates for both sizes of the randomized layouts were very low, about 5.4 wpm. This is the expected walk-up text entry rate with a soft keyboard bearing an unfamiliar layout. This empirical result allows us to reject a previous model of novice interaction that used Fitts' law for stylus movement and the Hick-Hyman law for visual scan time.

© All rights reserved MacKenzie and Zhang and/or Taylor and Francis

 
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MacKenzie, I. Scott, Kober, Hedy, Smith, Derek, Jones, Terry and Skepner, Eugene (2001): LetterWise: prefix-based disambiguation for mobile text input. In: Marks, Joe and Mynatt, Elizabeth D. (eds.) Proceedings of the 14th annual ACM symposium on User interface software and technology November 11 - 14, 2001, Orlando, Florida. pp. 111-120. Available online

A new technique to enter text using a mobile phone keypad is described. For text input, the traditional touchtone phone keypad is ambiguous because each key encodes three or four letters. Instead of using a stored dictionary to guess the intended word, our technique uses probabilities of letter sequences -- "prefixes" -- to guess the intended letter. Compared to dictionary-based methods, this technique, called LetterWise, takes significantly less memory and allows entry of non-dictionary words without switching to a special input mode. We conducted a longitudinal study to compare LetterWise to Multitap, the conventional text entry method for mobile phones. The experiment included 20 participants (10 LetterWise, 10 Multitap), and each entered phrases of text for 20 sessions of about 30 minutes each. Error rates were similar between the techniques; however, by the end of the experiment the mean entry speed was 36% faster with LetterWise than with Multitap.

© All rights reserved MacKenzie et al. and/or ACM Press

 
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Silfverberg, Miika, MacKenzie, I. Scott and Kauppinen, Tatu (2001): An Isometric Joystick as a Pointing Device for Handheld Information Terminals. In: Graphics Interface 2001 June 7-9, 2001, Ottawa, Ontario, Canada. pp. 119-126.

 
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MacKenzie, I. Scott and Jusoh, Shaidah (2001): An Evaluation of Two Input Devices for Remote Pointing. In: Little, Murray Reed and Nigay, Laurence (eds.) EHCI 2001 - Engineering for Human-Computer Interaction, 8th IFIP International Conference May 11-13, 2001, Toronto, Canada. pp. 235-250. Available online

2000
 
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Silfverberg, Miika, MacKenzie, I. Scott and Korhonen, Panu (2000): Predicting Text Entry Speed on Mobile Phones. In: Turner, Thea, Szwillus, Gerd, Czerwinski, Mary, Peterno, Fabio and Pemberton, Steven (eds.) Proceedings of the ACM CHI 2000 Human Factors in Computing Systems Conference April 1-6, 2000, The Hague, The Netherlands. pp. 9-16. Available online

We present a model for predicting expert text entry rates for several input methods on a 12-key mobile phone keypad. The model includes a movement component based on Fitts' law and a linguistic component based on digraph, or letter-pair, probabilities. Predictions are provided for one-handed thumb and two-handed index finger input. For the traditional multi-press method or the lesser-used two-key method, predicted expert rates vary from about 21 to 27 words per minute (wpm). The relatively new T9 method works with a disambiguating algorithm and inputs each character with a single key press. Predicted expert rates vary from 41 wpm for one-handed thumb input to 46 wpm for two-handed index finger input. These figures are degraded somewhat depending on the user's strategy in coping with less-than-perfect disambiguation. Analyses of these strategies are presented.

© All rights reserved Silfverberg et al. and/or ACM Press

1999
 
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MacKenzie, I. Scott and Zhang, Shawn X. (1999): The Design and Evaluation of a High-Performance Soft Keyboard. In: Altom, Mark W. and Williams, Marian G. (eds.) Proceedings of the ACM CHI 99 Human Factors in Computing Systems Conference May 15-20, 1999, Pittsburgh, Pennsylvania. pp. 25-31. Available online

The design and evaluation of a high performance soft keyboard for mobile systems are described. Using a model to predict the upper-bound text entry rate for soft keyboards, we designed a keyboard layout with a predicted upper-bound entry rate of 58.2 wpm. This is about 35% faster than the predicted rate for a QWERTY layout. We compared our design ("OPTI") with a QWERTY layout in a longitudinal evaluation using five participants and 20 45-minute sessions of text entry. Average entry rates for OPTI increased from 17.0 wpm initially to 44.3 wpm at session 20. The average rates exceeded those for the QWERTY layout after the 10th session (about 4 hours of practice). A regression equation (R{squared} = .997) in the form of the power-law of learning predicts that our upper-bound prediction would be reach at about session 50.

© All rights reserved MacKenzie and Zhang and/or ACM Press

 
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Douglas, Sarah A., Kirkpatrick, Arthur E. and MacKenzie, I. Scott (1999): Testing Pointing Device Performance and User Assessment with the ISO 9241, Part 9 Standard. In: Altom, Mark W. and Williams, Marian G. (eds.) Proceedings of the ACM CHI 99 Human Factors in Computing Systems Conference May 15-20, 1999, Pittsburgh, Pennsylvania. pp. 215-222. Available online

The ISO 9241, Part 9 Draft International Standard for testing computer pointing devices proposes an evaluation of performance and comfort. In this paper we evaluate the scientific validity and practicality of these dimensions for two pointing devices for laptop computers, a finger-controlled isometric joystick and a touchpad. Using a between-subjects design, evaluation of performance using the measure of throughput was done for one-direction and multi-directional pointing and selecting. Results show a significant difference in throughput for the multi-directional task, with the joystick 27% higher; results from the one-direction task were non-significant. After the experiment, participants rated the device for comfort, including operation, fatigue, and usability. The questionnaire showed no overall difference in the responses, and a significant statistical difference in only the question concerning force required to operate the device -- the joystick requiring slightly more force. The paper concludes with a discussion of problems in implementing the ISO standard and recommendations for improvement.

© All rights reserved Douglas et al. and/or ACM Press

 
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MacKenzie, I. Scott, Zhang, Shawn X. and Soukoreff, R. William (1999): Text Entry Using Soft Keyboards. In Behaviour and Information Technology, 18 (4) pp. 235-244.

Text entry rates are explored for several variations of soft keyboards. We present a model to predict novice and expert entry rates and present an empirical test with 24 subjects. Six keyboards were examined: the Qwerty, ABC, Dvorak, Fitaly, JustType, and telephone. At 8-10 wpm, novice predictions are low for all layouts because the dominant factor is the visual scan time, rather than the movement time. Expert predictions are in the range of 22-56 wpm, although these were not tested empirically. In a quick, novice test with a representative phrase of text, subjects achieved rates of 20.2 wpm (Qwerty), 10.7 wpm (ABC), 8.5 wpm (Dvorak), 8.0 wpm (Fitaly), 7.0 wpm (JustType), and 8.0 wpm (telephone). The Qwerty rate of 20.2 wpm is consistent with observations in other studies. The relatively high rate for Qwerty suggests that there is skill transfer from users' familiarity with desktop computers to the stylus tapping task.

© All rights reserved MacKenzie et al. and/or Taylor and Francis

 
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MacKenzie, I. Scott and Chang, Larry (1999): A Performance Comparison of Two Handwriting Recognizers. In Interacting with Computers, 11 (3) pp. 283-297.

An experiment is described comparing two commercial handwriting recognizers with discrete hand-printed characters. Each recognizer was tested at two levels of constraint, one using lowercase letters (which were the only symbols included in the input text) and the other using both uppercase and lowercase letters. Two factors -- recognizer and constraint -- with two levels each, resulted in four test conditions. A total of 32 subjects performed text-entry tasks for each condition. Recognition accuracy differed significantly among

© All rights reserved MacKenzie and Chang and/or Elsevier Science

1998
 
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MacKenzie, I. Scott and Oniszczak, Aleks (1998): A Comparison of Three Selection Techniques for Touchpads. In: Karat, Clare-Marie, Lund, Arnold, Coutaz, Jolle and Karat, John (eds.) Proceedings of the ACM CHI 98 Human Factors in Computing Systems Conference April 18-23, 1998, Los Angeles, California. pp. 336-343. Available online

Three methods of implementing the select operation on touchpads were compared. Two conventional methods -- using a physical button and using "lift-and-tap" -- were compared with a new method using finger pressure with tactile feedback. The latter employs a pressure-sensing touchpad with a built-in relay. The relay is energized by a signal from the device driver when the finger pressure on the pad surface exceeds a programmable threshold, and this creates both aural and tactile feedback. The pressure data are also used to signal the action of a button press to the application. In an empirical test with 12 participants, the tactile condition was 20% faster than lift-and-tap and 46% faster than using a button for selection. The result was similar on the ISO-recommended measure known as throughput. Error rates were higher with the tactile condition, however. These we attribute to limitations in the prototype, such as the use of a capacitive-sensing touchpad and poor mechanical design. In a questionnaire, participants indicated a preference for the tactile condition over the button and lift-and-tap conditions.

© All rights reserved MacKenzie and Oniszczak and/or ACM Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 
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Bellman, Tom and MacKenzie, I. Scott (1998): A Probabilistic Character Layout Strategy for Mobile Text Entry. In: Graphics Interface 98 June 18-20, 1998, Vancouver, British Columbia, Canada. pp. 168-176. Available online

1997
 
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Balakrishnan, Ravin and MacKenzie, I. Scott (1997): Performance Differences in the Fingers, Wrist, and Forearm in Computer Input Control. In: Pemberton, Steven (ed.) Proceedings of the ACM CHI 97 Human Factors in Computing Systems Conference March 22-27, 1997, Atlanta, Georgia. pp. 303-310. Available online

Recent work in computer input control has sought to maximize the use of the fingers in the operation of computer pointing devices. The main rationale is the hypothesis that the muscle groups controlling the fingers have a higher bandwidth than those controlling other segments of the human upper limb. Evidence which supports this, however, is inconclusive. We conducted an experiment to determine the relative bandwidths of the fingers, wrist, and forearm and found that the fingers do not necessarily outperform the other limb segments. Our results indicate that the bandwidth of the unsupported index finger is approximately 3.0 bits/s while the wrist and forearm have bandwidths of about 4.1 bits/s. We also show that the thumb and index finger working together in a pinch grip have an information processing rate of about 4.5 bits/s. Other factors which influence the relative performance of the different limbs in manipulation tasks are considered.

© All rights reserved Balakrishnan and MacKenzie and/or ACM Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 
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MacKenzie, I. Scott and Zhang, Shawn X. (1997): The immediate usability of graffiti. In: Graphics Interface 97 May 21-23, 1997, Kelowna, British Columbia, Canada. pp. 129-137. Available online

 
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MacKenzie, I. Scott and Oniszczak, Aleks (1997): The Tactile Touchpad. In: Extended Abstracts of the ACM SIGCHI 97 1997. pp. 309-310.

MacKenzie,I. Scott., and Oniszczak, A.The tactile touchpad, Extended Abstracts of the ACM SIGCHI '97, ACM, 1997, pp.309-310.

© All rights reserved MacKenzie and Oniszczak and/or ACM Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
1996
 
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Matias, Edgar, MacKenzie, I. Scott and Buxton, Bill (1996): One-Handed Touch Typing on a QWERTY Keyboard. In Human-Computer Interaction, 11 (1) pp. 1-27. Available online

"Half-QWERTY" is a new, one-handed typing technique designed to facilitate the transfer of two-handed touch-typing skill to the one-handed condition. It is performed on a standard keyboard with modified software or on a special half-keyboard with full-size keys. In an experiment using touch typists, hunt-and-peck typing speeds were surpassed after 3 to 4 hr of practice. Subjects reached 50% of their two-handed typing speed after about 8 hr. After 10 hr, all subjects typed between 41% and 73% of their two-handed speed, ranging from 23.8 to 42.8 words per minute (wpm). In extended testing, subjects achieved average one-handed speeds as high as 60 wpm and 83% of their two-handed rate. These results are important for providing access to disabled users and for designing compact computers.

© All rights reserved Matias et al. and/or Taylor and Francis

 
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Akamatsu, Motoyuki and MacKenzie, I. Scott (1996): Movement Characteristics using a Mouse with Tactile and Force Feedback. In International Journal of Human-Computer Studies, 45 (4) pp. 483-493.

A multi-modal mouse incorporating tactile and force feedback was tested in a target selection task with 12 subjects. Four feedback conditions (normal, tactile, force, tactile+force) were combined with three target distances and three target sizes. We found significant reductions in the overall movement times and in the time to stop the cursor after entering the target. This effect was particularly pronounced for the tactile condition and for small targets. However, compared to normal feedback, error rates were higher with the tactile and tactile+force conditions. The motor-sensory bandwidth calculated using Fitt's law, normalized for spatial variability, was highest in the presence of tactile feedback (6.4 bits/s). This was followed by tactile+force (6.2 bits/s), normal (5.9 bits /s), and force feedback (5.8 bits/s). These results indicate that modifying a mouse to include tactile feedback, and to a lesser extent, force feedback, offers performance advantages in target selection tasks.

© All rights reserved Akamatsu and MacKenzie and/or Academic Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
1995
 
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Soukoreff, R. William and MacKenzie, I. Scott (1995): Theoretical Upper and Lower Bounds on Typing Speed using a Stylus and a Soft Keyboard. In Behaviour and Information Technology, 14 (6) pp. 370-379.

A theoretical model is presented to predict upper- and lower-bound text-entry rates using a stylus to tap on a soft QWERTY keyboard. The model is based on the Hick-Hyman law for choice reaction time, Fitts' law for rapid aimed movements, and linguistic tables for the relative frequencies of letter-pairs, or digrams, in common English. The model's importance lies not only in the predictions provided, but in its characterization of text-entry tasks using keyboards. Whereas previous studies only use frequency probabilities of the 26 x 26 digrams in the Roman alphabet, our model accommodates the space bar -- the most common character in typing tasks. Using a very large linguistic table that decomposes digrams by position-within-words, we established start-of-word (space-letter) and end-of-word (letter-space) probabilities and worked from a 27 x 27 digram table. The model predicts a typing rate of 8.9wpm for novices unfamiliar with the QWERTY keyboard, and 30.1 wpm for experts. Comparisons are drawn with empirical studies using a stylus and other forms of text entry.

© All rights reserved Soukoreff and MacKenzie and/or Taylor and Francis

 
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McQueen, Craig, MacKenzie, I. Scott and Zhang, Shawn X. (1995): An extended study of numeric entry on pen--based computers. In: Graphics Interface 95 May 17-19, 1995, Quebec, Quebec, Canada. pp. 215-222.

1994
 
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MacKenzie, I. Scott and Riddersma, Stan (1994): Effects of Output Display and Control-Display Gain on Human Performance in Interactive Systems. In Behaviour and Information Technology, 13 (5) pp. 328-337.

Human performance comparisons on interactive systems were drawn between output displays (CRT and LCD) across settings of control-display gain. Empirical evidence was sought in light of the common feeling in the user community that motor-sensory tasks are more difficult on a system equipped with an LCD display vs. a CRT display. In a routine target acquisition task using a mouse, movement times were 34% longer and motor-sensory bandwidth was 25% less when the output display was an LCD vs. a CRT. No significant difference in error rates was found. Control-display (C-D) gain was tested as a possible confounding factor; however, no interaction effect was found. There was a significant, opposing main effect for C-D gain on movement time and error rates, illustrating the difficulty in optimizing C-D gain on the basis of movement time alone.

© All rights reserved MacKenzie and Riddersma and/or Taylor and Francis

 
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MacKenzie, I. Scott, Nonnecke, Blair, Riddersma, Stan, McQueen, Craig and Meltz, Malcolm (1994): Alphanumeric Entry on Pen-Based Computers. In International Journal of Human-Computer Studies, 41 (5) pp. 775-792.

Two experiments were conducted to compare several methods of numeric and text entry for pen-based computers. For numeric entry, the conditions were hand printing, tapping on a soft keypad, stroking a moving pie menu, and stroking a pie pad. For the pie conditions, strokes are made in the direction that numbers appear on a clock face. For the moving pie menu, strokes were made directly in the application, as with hand printing. For the pie pad, strokes were made on top of one another on a separate pie pad, with the results sent to the application. Based on speed and accuracy, the entry methods from best to worst were soft keypad (30 wpm, 1.2% errors), hand printing (18.5 wpm, 10.4% errors), pie pad (15.1 wpm, 14.6% errors), and moving pie menu (12.4 wpm, 16.4% errors). For text entry, the conditions were hand printing, tapping on a soft keyboard with a QWERTY layout, and tapping on a soft keyboard with an ABC layout (two rows of sequential characters). Tapping on the soft QWERTY keyboard was the quickest (23 wpm) and most accurate (1.1% errors) entry method. Hand printing was slower (16 wpm) and more error prone (8.1% errors). Tapping on the soft ABC keyboard was very accurate (0.6% errors) but was slower (13 wpm) than the other methods. These results represent the first empirical tests of entry speed and accuracy using a stylus to tap on a soft keyboard. Although handwriting (with recognition) is touted as the entry method of choice for pen-based computers, the much simpler technique of tapping on a soft keyboard is faster and more accurate.

© All rights reserved MacKenzie et al. and/or Academic Press

 
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MacKenzie, I. Scott and Buxton, Bill (1994): Prediction of Pointing and Dragging Times in Graphical User Interfaces. In Interacting with Computers, 6 (2) pp. 213-227.

An experiment is described which demonstrates that the point-drag sequence common on interactive systems can be modelled as two separate Fitts law tasks -- a point-select task followed by a drag-select task. Strong prediction models were built; however, comparisons with previous models were not as close as the standard error coefficients implied. Caution is therefore warranted in follow-up applications of models built in research settings. Additionally, the previous claim that target height is the appropriate substitute for target width in calculating Fitts' index of difficulty in dragging tasks was not supported. The experiment described varied the dragging target's width and height independently. Models using the horizontal width of the drag target or the smaller of the target's width or height outperformed the target height model.

© All rights reserved MacKenzie and Buxton and/or Elsevier Science

 
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McQueen, Craig, MacKenzie, I. Scott, Nonnecke, Blair, Riddersma, Stan and Meltz, Malcolm (1994): A comparison of four methods of numeric entry on pen--based computers. In: Graphics Interface 94 May 18-20, 1994, Banff, Alberta, Canada. pp. 75-82.

 
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MacKenzie, I. Scott, Nonnecke, R. Blair, McQueen, J. Craig, Riddersma, Stan and Meltz, Malcolm (1994): A Comparison of Three Methods of Character Entry on Pen-Based Computers. In: Proceedings of the Human Factors and Ergonomics Society 38th Annual Meeting 1994. pp. 330-334.

Methods for entering text on pen-based computers were compared with respect to speed, accuracy, and user preference. Fifteen subjects entered text on a digitizing display tablet using three methods: hand printing, QWERTY-tapping, and ABC-tapping. The tapping methods used display-based keyboards, one with a QWERTY layout, the other with two alphabetic rows of 13 characters.

© All rights reserved MacKenzie et al. and/or Human Factors Society

 
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Akamatsu, Motoyuki, Sato, Sigeru and MacKenzie, I. Scott (1994): Multimodal Mouse: A Mouse-Type Device with Tactile and Force Display. In Presence: Teleoperators and Virtual Environments, 3 (1) pp. 73-80.

1993
 
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Matias, Edgar, MacKenzie, I. Scott and Buxton, Bill (1993): Half-QWERTY: A One-Handed Keyboard Facilitating Skill Transfer from QWERTY. In: Ashlund, Stacey, Mullet, Kevin, Henderson, Austin, Hollnagel, Erik and White, Ted (eds.) Proceedings of the ACM CHI 93 Human Factors in Computing Systems Conference April 24-29, 1993, Amsterdam, The Netherlands. pp. 88-94. Available online

Half-QWERTY is a new one-handed typing technique, designed to facilitate the transfer of two-handed typing skill to the one-handed condition. It is performed on a standard keyboard, or a special half keyboard (with full-sized keys). In an experiment using touch typists, hunt-and-peck typing speeds were surpassed after 3-4 hours of practice. Subjects reached 50% of their two-handed typing speed after about 8 hours. After 10 hours, all subjects typed between 41% and 73% of their two-handed speed, ranging from 23.8 to 42.8 wpm. These results are important in providing access to disabled users, and for the design of compact computers. They also bring into question previous research claiming finger actions of one hand map to the other via spatial congruence rather than mirror image.

© All rights reserved Matias et al. and/or ACM Press

 
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MacKenzie, I. Scott and Buxton, Bill (1993): A Tool for the Rapid Evaluation of Input Devices Using Fitts' Law Models. In ACM SIGCHI Bulletin, 25 (3) pp. 58-63. Available online

A tool for building Fitts' law models is described. MODEL BUILDER runs on the Apple Macintosh using any device which connects to the Apple Desktop Bus. After 16 blocks of trials taking about 4-5 minutes, the program provides an immediate (albeit tentative) statistical analysis, showing the coefficients in the prediction equation, the coefficient of correlation, and a regression line with scatter points. MODEL BUILDER can be retrieved anonymously by researchers, educators, developers, or anyone with access to INTERNET through file-transfer-protocol (FTP).

© All rights reserved MacKenzie and Buxton and/or ACM Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 
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MacKenzie, I. Scott and Ware, Colin (1993): Lag As a Determinant of Human Performance in Interactive Systems. In: Proceedings of ACM INTERCHI 93 1993. pp. 488-493.

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
1992
 
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MacKenzie, I. Scott and Buxton, Bill (1992): Extending Fitts' Law to Two-Dimensional Tasks. In: Bauersfeld, Penny, Bennett, John and Lynch, Gene (eds.) Proceedings of the ACM CHI 92 Human Factors in Computing Systems Conference June 3-7, 1992, Monterey, California. pp. 219-226. Available online

Fitts' law, a one-dimensional model of human movement, is commonly applied to two-dimensional target acquisition tasks on interactive computing systems. For rectangular targets, such as words, it is demonstrated that the model can break down and yield unrealistically low (even negative!) ratings for a task's index of difficulty (ID). The Shannon formulation is shown to partially correct this problem, since ID is always >= 0 bits. As well, two alternative interpretations of "target width" are introduced that accommodate the two-dimensional nature of tasks. Results of an experiment are presented that show a significant improvement in the model's performance using the suggested changes.

© All rights reserved MacKenzie and Buxton and/or ACM Press

 
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MacKenzie, I. Scott (1992): Fitts' Law as a Research and Design Tool in Human-Computer Interaction. In Human-Computer Interaction, 7 (1) pp. 91-139.

According to Fitts' law, human movement can be modeled by analogy to the transmission of information. Fitts' popular model has been widely adopted in numerous research areas, including kinematics, human factors, and (recently) human-computer interaction (HCI). The present study provides a historical and theoretical context for the model, including an analysis of problems that have emerged through the systematic deviation of observations from predictions. Refinements to the model are described, including a formulation for the index of task difficulty that is claimed to be more theoretically sound than Fitts' original formulation. The model's utility in predicting the time to position a cursor and select a target is explored through a review of six Fitts' law studies employing devices such as the mouse, trackball, joystick, touchpad, helmet-mounted sight, and eye tracker. An analysis of the performance measures reveals tremendous inconsistencies, making across-study comparisons difficult. Sources of experimental variation are identified to reconcile these differences.

© All rights reserved MacKenzie and/or Taylor and Francis

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 
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MacKenzie, I. Scott (1992): Movement time prediction in human--computer interfaces. In: Graphics Interface 92 May 11-15, 1992, Vancouver, British Columbia, Canada. pp. 140-150.

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
1991
 
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MacKenzie, I. Scott, Sellen, Abigail and Buxton, Bill (1991): A Comparison of Input Devices in Elemental Pointing and Dragging Tasks. In: Robertson, Scott P., Olson, Gary M. and Olson, Judith S. (eds.) Proceedings of the ACM CHI 91 Human Factors in Computing Systems Conference April 28 - June 5, 1991, New Orleans, Louisiana. pp. 161-166. Available online

An experiment is described comparing three devices (a mouse, a trackball, and a stylus with tablet) in the performance of pointing and dragging tasks. During pointing, movement times were shorter and error rates were lower than during dragging. It is shown that Fitts' law can model both tasks, and that within devices the index of performance is higher when pointing than when dragging. Device differences also appeared. The stylus displayed a higher rate of information processing than the mouse during pointing but not during dragging. The trackball ranked third for both tasks.

© All rights reserved MacKenzie et al. and/or ACM Press

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
1989
 
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MacKenzie, I. Scott (1989): A Note On the Information Theoretic Basis for Fitts' Law. In Journal of Motor Behavior, 21 pp. 323-330.

 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 Cited in the following chapter:

Fitts's Law: [/encyclopedia/fitts_law.html]


 
 
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