HUMAN-COMPUTERINTERACTION,1996, Volume 11, pp. 1-27
`Copyright © 1996, Lawrence Erlbaum Associates, Inc.
`
`
`
`One-Handed Touch Typing on a
`QWERTY Keyboard
`
`Edgar Matias
`The Matias Corporation
`
`I. Scott MacKenzie
`University of Guelph
`
`William Buxton
`University of Toronto
`
`
`
`ABSTRACT
`
`“Half-QWERTY”is a new, one-handed typing technique designed tofacilitate
`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-key-
`board with full-size keys. In an experiment using touch typists, hunt-and-peck
`typing speeds were surpassed after 3 to 4 hr ofpractice. 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
`
`Edgar Matias is a student at the University of Toronto, a memberof the Input
`Research Group in the Department of Computer Science at the University of
`Toronto, and President of The Matias Corporation. I. Scott MacKenzie is a
`computer scientist whose interests include performance measurement, prediction,
`and modeling for human-computerinteraction, he is an Assistant Professor in the
`Department of Computing and Information Science at the University of Guelph.
`William Buxton is a computer scientist with an interest in the human aspects of
`technology, input to computer systems, and collaborative work at a distance; heis
`an Associate Professor in the Department of Computer Science at the University
`of Toronto and Director of Interaction Research for Alias Research, Toronto.
`
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`MATIAS, MACKENZIE, BUXTON
`2
`
`
`CONTENTS
`
`1, INTRODUCTION
`2. HALF-QWERTY CONCEPT
`2.1, Flip Operation
`2.2. Modifier Keys
`2.3. Which Hand to Use?
`2.4. Design Space
`2.5. Hand Symmetry, Critical Invariance, and Skill Transfer
`3. SKILL TRANSFER EXPERIMENT
`3.1. Method
`3.2. Results
`Temporal Analysis
`Error Analysis
`Speed Analysis
`3.3. Discussion
`Extended Sessions
`Modeling Expert Performance
`Skill Transfer Between Hands and Flip Inversion
`4. DESIGN IMPLICATIONS
`5. CONCLUSIONS
`
`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.
`
`
`
`1, INTRODUCTION
`
`The QWERTY keyboard has been much maligned overthe years. It
`has been called, by various authors “less than efficient” (Noyes, 1983, p.
`269), “drastically suboptimal” (Gould, 1987, p. 16), “one of the worst
`possible arrangement[s] for touch typing” (Noyes, 1983, p. 267), “the
`wrong standard” (Gould, 1987, p. 23), and a “technological dinosaur”
`(Gopher & Raij, 1988, p. 601). Despite this, it has for various reasons
`(Litterick, 1981; Noyes, 1983; Potosnak, 1988) stoodthetest of time—a fact
`often overlooked by designersof alternative keyboards. Until recently, the
`massive skill base of QWERTY typists has beenlargely ignored, with new
`designs favoring “better” layouts, In this article, we are more conservative,
`preferring instead to argue that QWERTY is not an evolutionary dead
`end.
`
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`ONE-HANDED TOUCH TYPING
`
`3
`
`Our modern method of typing by touch was originally popularized by
`L. V. Longley and F. E. McGurrin in thelatter part of the 19th century
`(Cooper, 1983). Curiously, despite more than 100 years of industrializa-
`tion, QWERTY and the Longley and McGurrin technique remain largely
`unchanged. One of Longley’s students would be comfortable on a modern
`computer keyboard, despite the alien machinery surrounding it. Similarly,
`we believe that this student would havelittle trouble acquiring the new,
`complementary, one-handed typing technique that we are about to pro-
`pose. This article describes the new technique, with which a two-handed
`touch typist with very little retraining can type with one hand on a
`software-modified QWERTY keyboard. In effect, it is the one-handed
`equivalent of Longley and McGurrin’s original eight-finger, two-handed
`typing technique. Wecall the technique Half-QWERTY because it uses
`only half of a QWERTY keyboard.
`The present study examines the degree to which skill transfers from
`QWERTYto HalfQWERTYkeyboardsfor typists already skilled in the
`use of a QWERTYkeyboard. This was tested in an experiment using a
`standard keyboard for both the one-handed and two-handedconditions.
`2. HALF-QWERTY CONCEPT!
`
`Most one-handed keyboards are chord* keyboards. HalfQWERTYis
`not. The design builds on two principles:
`
`1. A user’s ability to touch-type on a standard QWERTY keyboard.
`2. The fact that human hands are symmetrical—one hand is a mirror
`image of the other—and the brain controls them as such.
`
`A Half-QWERTY keyboard consists of all the keys used by one hand to
`type on a standard QWERTY keyboard, with the keys of the other hand
`unused or absent. Whenthe spacebar is depressed, the missing characters
`are mapped onto the remaining keys in a mirror image (Figure 1), such
`that the typing hand makes movements homologousto those previously
`performed by the other hand. For example, in two-handed typing, the
`letter J is typed using the index finger of the right hand in the home row
`(see Figure 1, right side). Using the Half- QWERTYtechnique,/is entered
`with the left hand by holding down the spacebar and pressing the F key
`
`1, U.S. Patent No. 5,288,158. European Patent No.0,489,792. Australian Patent
`No. 647,750. Other patents pending. Half- QWERTYis a trademark of The Matias
`Corporation.
`2. On chord keyboards, operators type by pressing one or more keys simulta-
`neously. For example, pressing the A key types 4; pressing the B key types B;
`pressing both keys simultaneously types some other arbitrary letter. Thus, a
`five-key chord keyboard can generate 31 different characters (31 = 2° - L).
`
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`4
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`MATIAS, MACKENZIE, BUXTON
`
`Tab
`
`Figure 7. Left- and right-hand HalfQWERTY layouts on a standard QWERTY key-
`board. When a key is depressed, the character in the upperleft of the key is entered.
`When preceded by holding down the spacebar, the character in the lower right is
`entered. Note: Copyright © 1992 by The Matias Corporation. Used with permission.
`
`Deleteead=noat
`
`(index finger of the left hand in the home row; see Figure 1, left side).
`Notice that in both cases the index finger is in the home row to type /.
`Thus, using the spacebar as a modifier, a typist can generate the characters
`of either side of a full-size keyboard using only one hand. Wecall this
`mirror-image remapping of the keyboard the /lig operation.
`
`2.1. Flip Operation
`
`Theflip operation consists of the following:
`
`1. A spacebar capable of acting as a modifier key, in addition toits
`traditional role.
`2. The mirror-image remapping of one half or both halves of a stan-
`dard QWERTY keyboard, when the spacebar is depressed and
`held.
`
`A state diagram governingtheflip operation is shown in Figure 2. In State
`0, the spacebar is up; in States 1 and 2, the spacebar is depressed. On a
`normal keyboard, depressing the spacebar generates a space character. If
`the spacebar is held down beyond a timeout value, space characters are
`generated repeatedly until the bar is released. Therefore, to generate one
`space,a typist depresses and releases the spacebar within a timeout value.
`Typing a space using Half‘QWERTY works the same way. Depressing and
`releasing the spacebar within a timeout generates a space character.’ In the
`state diagram,this corresponds to changing from State 0 to State 1 to State
`0. In other words, if the spacebar is released while in State 1, a space is
`generated. This differs slightly from standard QWERTY. In QWERTY,
`
`3. For this experiment, the timeout was 16/60 sec (or 267 msec).
`
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`ONE-HANDED TOUCH TYPING
`
`5
`
`Figure 2. Spacebar state-transition diagram. If (state > 0) {key presses are
`flipped};
`if (state == 1)
`{Space Up generates space character}.
`Note: Copyright © 1992 by The Matias Corporation. Used with permission.
`
`Space Up
`
`
`
`
` Space Up
`Hit A Key
`
` Space Down
`Space Timeout
`
`in Half-
`
`the space is generated on the depression of the spacebar;
`QWERTY,it is generated on the release.
`If a character key is struck while the spacebar is depressed (in State 1 or
`2), that key is “flipped” (i.e., the mirror-image character is entered, and the
`state changes to 2-the “flip state”). While in State 2, the spacebar acts
`exactly like a modifier key: If a character key is struck,it is flipped,if the
`spacebar is released, the state returns to 0, and no space character is
`generated. State 2 is also the timeout state. If the user depresses the
`spacebar (State 1) and holds it down past the timeout value, the state
`changes to 2. The timeout serves to reduce the number of erroneous
`spaces generated as a side effect of using the spacebar as a modifier key.
`Occasionally, a typist depresses the spacebar with the intention of mirror-
`ing thestate of another key but then changeshis or her mind andreleases
`the spacebar. Without the timeout, such actions would result in an un-
`wanted space character. With it, the problem is alleviated.
`We summarize the state diagram as follows. While in State 0 (the null
`state), the keyboard behaves as a QWERTY keyboard would.State | is
`ambiguous: It is not immediately clear whether a space character or the
`flipping of a subsequent key is desired. In State 2, the spacebar acts as a
`modifier key, flipping any character keys struck.
`
`2.2. Modifier Keys
`
`Modifier keys do not generate codes themselves but modify the cade
`for a subsequentkey struck while the modifier is active. Figure 3 showsthe
`state diagram for the Shift key, as used in our experiment.If other modifier
`keys were implemented, they would behave in a similar manner. Odd-
`numbered states (1, 3, 5) indicate that the modifier key is depressed;
`even-numberedstates (0, 2, 4) correspondto the release of the key. If the
`state is greater than 0, then the modifier key is active.
`
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`6
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`MATIAS, MACKENZIE, BUXTON
`
`Figure 3. Modifier-key state-transition diagram. If (state > 0) {modifier key is
`active}. Note: Copyright © 1992 by The Matias Corporation. Used with permission.
`
`Hit. A Key
`
`Modifier Down
`
`Modifier Up
`
`Hit A Key
`
`Hit A Key
`
`Modifier Up
`
`
`
`
` Modifier Down
`Hit A Kay
`
`
`Modifier Up
`
`Hit A Key
`
`Modifier Down
`
`Ona regular keyboard, a modifier key is active when it is depressed and
`inactive when it is released. This corresponds to States 5 and 0, respec-
`tively, in Figure 3. If a character key is struck at any time while the
`modifier key is depressed (ie., odd-numbered states),
`the state im-
`mediately jumpsto 5, thus reverting to standard modifier-key behavior. In
`one-handed typing, however, it is convenient not to require continuous
`depression of a modifier key for it to be active. Therefore, we supply a
`“latch” mechanism, commonly known as Sticky Keys. Depressing and re-
`leasing a modifier key once (State 0 to 1 to 2) activate it for the next key
`struck. This is useful for capitalizing thefirst letter of a word, for example.
`Depressing and releasing the modifier key twice (State 0 to 1 to 2 ta 3 to
`4) lock it until it is unlocked by depressing andreleasing it again (State 4
`to 5 to 0). The lock is useful for capitalizing entire words. Thus, Sticky
`Keys allow one finger to do the work of several when performing key
`sequences that would otherwise require the simultaneous depression of
`two or more keys.
`
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`ONE-HANDED TOUCH TYPING
`
`7
`
`Figure 4. Half-keyboard design space.
`
`Predicted Speed
`
`Keystrokes
`
`1.87
`
`53%
`
`61%
`
`65%
`
`70%
`74%
`
`90%
`
`
`
`oo SO
`
`2.3. Which Hand to Use?
`
`Given the keyboard already described, we must now decide which
`hand is “best” for one-handed typing. In general, we believe it is the
`nondominant hand. This would free the more dexterous, dominant hand
`to use a mouse(or other device} to enter spatial information. Also, Provins
`and Glencross (1968) found that, for right-handed typists, the nondomin-
`antleft hand performedas well as or better than the right hand. Therefore,
`generally we see no reason for using the dominant hand for one-handed
`typing. It is best saved for spatial input,
`to which it
`is better suited
`(Kabbash, MacKenzie, & Buxton, 1993).
`
`2.4. Design Space
`
`How optimal is Half‘QWERTY? Or, stated differently, where does
`Half-QWERTYlie in the design space of possible half-keyboards? The
`design works by substituting extra keystrokes (depressions of the spacebar)
`for the presence of the other hand. Thus, a simple way of determining its
`efficiency is to calculate the numberof additional keystrokes required for
`one-handedtypingrelative to two-handedtyping. This is shown in Figure
`4, The comparison is based on an analysis of the textfile later used for our
`experiment. In the two-handed calculation, capitalized letters not pre-
`ceded by another capitalized letter were counted as two keystrokes; all
`others counted as one. In each one-handedcalculation,flipped characters
`not preceded by another flipped character were counted as two key-
`strokes; all others were counted as one; for capitalized letters, an extra
`keystroke was added.
`
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`8
`
`MATIAS, MACKENZIE, BUXTON
`
`A hypothetical optimal layout would require approximately 11% more
`keystrokes than two-handed typing, whereas a suboptimal layout would
`require about 87% more. By optimal, we mean a layout for which the 15
`mostfrequently used letters—e, £, a, 0, n, 1, i, 5, h, d, lf, ¢, m, u (Pratt, 1942;
`Zettersten, 1978)—are nonflipped (one or two keystrokes); on a suboptimal
`layout,
`these letters would be flipped (as many as three keystrokes).
`Because our subjects would be using their (nondominant) left hand, Half-
`QWERTYtyping would require 35% more keystrokes than two-handed
`typing. Of the layouts we have tested that were designed for two-handed
`typing, including several not shown in the figure,
`left-hand Half-
`QWERTYis the closest to being optimal. This is a happy accident, given
`that the QWERTYlayout.was not designed to support one-handedtyping.
`Note, however, that this is only true of the left hand. Right-hand Half-
`QWERTYis considerably less efficient, requiring 21% more keystrokes
`than the left hand—63%more than two-handed typing. Thus, optimally,
`the left-hand layout should be used for Half-QWERTY typing.
`Ourcalculations show that a balanced layout (one favoring neither left
`nor right hand) would require approximately 49% more keystrokes than
`two-handed typing. If we were to insert this value into our graph, we
`would findthatit lies halfway between eachof the left-hand andright-hand
`layouts shown. The line segmentat the bottom of Figure 4 illustrates the
`symmetry of this relation. We can easily see the (predicted) performance
`trade-off between hands for a given layout. This also suggests that there is
`no such thing as a “perfect” keyboard layout. Those optimized for two-
`handedtypingareless efficient for one-handed typing. Those favoring one
`hand handicap the performanceof the other.
`Finally, we extend this notion of extra keystrokes to predict roughly
`what percentage of two-handed speed a given one-handed typist can
`achieve. If the keystroke ratio of one-handed to two-handed typing is
`1.35:1, we can take its reciprocal (1:1.35 = .74) as a basis for determining
`one-handed typing speed as a percentage of the two-handedrate. Thus,it
`should be possible for someone using a left-hand HalfQWERTY key-
`board (typing in English) to achieve 74% of his or her two-handed typing
`speed. As weshall see, this is a fairly accurate baseline prediction.
`
`2.5. Hand Symmetry, Critical Invariance, and Skill Transfer
`
`Half-QWERTYis based on the principle that the human brain controls
`typing movements according to the finger used rather than the spatial
`position of the key. Thus, the finger used to press a key is the critical
`invariant—the critical similarity. that is maintained across the training and
`transfer tasks~in the transfer of skill from QWERTY to Half-QWERTY.
`Lintern (1991) wrote:
`
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`ONE-HANDED TOUCH TYPING
`
`9
`
`those that pose a meaningful learning
`If critical invariants (specifically,
`challenge) remain unchanged,[skill] transfer will be high even when many
`other features of the environment, context, or task are changed ... If an
`operator’s perceptual sensitivity to critical invariants can be improved,that
`enhancedsensitivity will serve to facilitate transfer. (p. 262)
`
`Our mirror-image encoding scheme(already described) follows from this,
`and our experimental procedure (to be described) was designed to en-
`hance subjects’ perceptual sensitivity to critical invariants.‘
`In the following section, we describe an experiment intended to test the
`degree to which skill transfers from QWERTY to Half; QWERTYkey-
`boards amongskilled touch typists.
`
`3. SKILL TRANSFER EXPERIMENT
`
`3.1. Method
`
`Subjects. Ten right-handed, computer-literate QWERTY touch typ-
`ists from a local university served as paid volunteers. Subjects used their
`nondominant(left) hand when typing with one hand. The Edinburgh
`Inventory (Olfield, 1971) was given to determine handedness. All subjects
`were self-acclaimed touch typists, and their first-session (two-handed)
`speeds ranged from 38 words per minute (wpm) to 74 wpm. The mean was
`58 wpm.
`
`Equipment. Tasks were performed on Apple Macintosh II computers
`running System 7 and using Apple (Model M0116) keyboards. A card-
`board shield was placed between the subjects’ hands and eyes to prevent
`them from looking at the keyboard.
`A software package was developed that mimicked Typing Tutor IV,”
`with the subject’s typing displayed beneath the input text (Figure 5). In
`addition to calculating speed and error rates, our software recorded com-
`plete keystroke-level data.
`
`Procedure. Each subject participated in 10 sessions (no more than one
`session a day). Each session included a two-handed pretest, multiple
`blocks of one-handed typing, and a two-handedposttest. In addition, three
`subjects underwent prolonged testing. One subject participated in 20
`
`4. A rival encoding schemeis thatof spatial congruence, which maintains that
`the spatial position of the keyis the critical invariant. There is disagreement in the
`literature as to which of these schemes is “better.” For a review of the relevant
`literature, see Matias, MacKenzie, and Buxton (1993).
`5, Kriya Systems, Inc. Published by Simon & Schuster Software, Gulf+Western
`Building, One Gulf+Western Plaza, New York, NY 10023.
`
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`10
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`MATIAS, MACKENZIE, BUXTON
`
`Figure 5. Screen snapshot of experiment software. Note that subjects must type in
`synchronization with the displayed text. Out-of-synchronization characters are
`treated as errors.
`
`#| When the term comprehensive and vast,
`4) When the term comprehensive and vast,
`By
`.
`MMMRAXKKKMKKX |
`x
`i applied to human
`beings, it is a form of praise, while the
`a applied to human beings it il a form of praT
`opposite,
`light and small would be to berate the same.
`
`jukochodai, is
`jukochodai,
`is
`
`However, when these terms are applied to the industrial
`
`sessions, two others participated in 40 sessions each. All one-handed
`typing was performed with the left hand, and subjects were not allowed to
`rest their right hand on the keyboard.
`The Delete key was disabled so that subjects could not correct errors. A
`beep was heard for every error made. Subjects were instructed to type as
`quickly and accurately as possible while remaining in synchronization
`with the input text. They werealso told to avoid long pauses of thought: If
`they were unsure ofa given letter, they should guess and continuetyping.
`Subjects could rest as desired between blocks.
`The text for all typing was taken from a novel aboutJapanese-American
`relations. The text consisted of only uppercase and lowercase letters and
`simple punctuation (comma and period). This text differs from that of
`most of the typing studies we found in the literature, which tested lower-
`case typing only (Gopher & Raij, 1988; Grudin, 1983; Munhall & Ostry,
`1983; Provins & Glencross, 1968).
`Thefirst session included special one-handed blocks designed to ease
`subjects into understanding the operation of the keyboard. These intro-
`ductory blocks were performed after the two-handed pretest but before
`starting the regular one-handed typing task described earlier. In the first
`block, subjects typed whatever they pleased in orderto familiarize them-
`selves with the one-handed layout—particularly with the operation of the
`Shift key and of the spacebar timeout. After this practice block, subjects
`typed three blocks of text of gradually increasing complexity: left, right,
`and left-plus-right text blocks. For these blocks, the amount of mode
`switching was restricted in order to reinforce the idea that finger move-
`
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`ONE-HANDED TOUCH TYPING
`
`ll
`
`ments are homologously preserved in the transition from QWERTY to
`Half-QWERTYtyping. The left block consisted of text entirely from the
`left side of a QWERTYkeyboard, makingit similar to two-handedtyping
`but requiring only the left hand. Similarly, the right block consisted of only
`right-sided text. This required that the spacebar be held down continu-
`ously to mirror the layout of the keyboard. It was released only to type
`space characters. The left-plus-right block consisted of text of both types
`mixed together. Thus, for this block it was necessary to switch modes only
`between words that required it. Subjects were told that, when typing a
`right-sided wordusingthe left hand, making the corresponding movement
`with their right hand is a helpful memory reference and that, if a mode
`error is madeat the beginning of a word,thestate of the spacebar must be
`changedto type therest of the word correctly.
`
`Design. The experiment wasan investigation of the learning potential
`of the Half QWERTYkeyboard. Each 50-min session consisted of a series
`of text blocks typed by the subject. The block length was set to four lines
`of 60 characters in the first session (using Courier 14-point type) and was
`increasedto six lines (andlater eight lines) when subjects managedto type
`30 or more one-handedblocksin one session. Subjects completed as many
`one-handed blocks as were possible in a session, ranging from 1 to 34
`blocks, depending on speed and the amountofrest. Two-handedpretests
`and posttests were also given in order to test for interference effects of
`one-handed typing on two-handed typing.
`The dependent measures were typing speed and error rate. Typing
`speeds are in wpm, and a wordis defined as five characters (including
`spaces). Errorrates are given as a percentageoftotal keystrokes(the lower
`the better). Subjects’ typing was displayed beneath the input text, as
`consistent with Typing Tutor IV (Figure 5). Subjects had to type the
`correct character in the correct position. Thus, they had to type in synchro-
`nization with the text on the screen. If they fell out of synchronization,
`each out-of-synchronization character was countedas an error, resulting in
`whatwelater refer to as the cumulative error rate. This is contrasted with the
`chunk error rate, whereby consecutive errors are considered a single error.
`Thebasis for analyzing errors as such is expanded onlater.
`This strict interface was chosen for pragmatic reasons—specifically, the
`very large amount of data collected (more than 25 megabytes!) and the
`need to automate the data analysis. If subjects were allowed to type freely,
`the analysis would be extremely difficult to automate.
`Wecollected complete keystroke-level data, which allowed detailed
`examinationofinterkey timings across states (Space Up, Space Down) and
`fingers, and of error patterns across letters and state sequences.
`
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`12
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`MATIAS, MACKENZIE, BUXTON
`
`Figure 6. Mean performance scores for speed and accuracy on one-handed (1H) and
`two-handed (2H) typing over 10 seasions.
`SLARLSSAARI
`Chunk-
`Cumulative
`ChunkErrors
`Adjusted
`
`Errors(%)
`(%)
`_Speed (wpm)
`
`1H
`2H
`1H
`2H
`1H
`2H
`
`Speed (wpm)
`1H
`2H
`
`Session
`
`570
`11.7
`2.19
`12.22
`3.44
`15.16
`58.3
`13.2
`1
`58.3
`16.6
`2.20
`9.00
`3.55
`10.90
`59.5
`18.2
`2
`61.2
`19.6
`1.64
`7.36
`2.53
`8.74
`62.1
`21.1
`3
`60.2
`22.7
`2.16
`7.14
`3.11
`8.50
`614
`24.4
`4
`62.1
`25.4
`2.30
`6.68
`3.52
`7.99
`63.5
`271
`5
`61.6
`27.3
`2.31
`6.32
`3.59
`7.69
`62.9
`29.1
`6
`62.3
`28.9
`2.15
`5.73
`3.67
`6.82
`63.6
`30.6
`7
`63.1
`29.8
`2.14
`5.87
`3.58
`740
`64.5
`31.6
`8
`9
`33.6
`66.1
`7.28
`3.30
`5.83
`1.90
`31.7
`65.0
`10
`34.7
`65.0
`7.36
`4.14
`5.77
`2.68
`32.7
`63.4
`
`
`3.2. Results
`
`Subjects were able to adapt to Half QWERTY typing very quickly. As
`shownin Figure 6, Session | resulted in an average speed of 13.2 wpm with
`more than 84% accuracy. This performance is impressive, especially con-
`sidering how little training was given. For instance, subjects were not
`required to memorize the layout before starting the one-handed typing
`task and therefore had torely entirely on skill transfer from two-handed
`typing. One-handed speed improved significantly over the 10 sessions,
`FQ, 81) = 779, p < .0001, to reach a 10th-session average of 34.7 wpm.
`Improvement in the one-handed cumulative error rate was alsostatisti-
`cally significant, A{9, 81) = 13.4, p< .0001, dropping to an average of 7.36%
`errors in the 10th session.° This is less than twice the rate of errors made
`in two-handed typing. (The distinction between cumulative and chunk
`errors is drawn later.)
`Worthyof note is that two-handed typing speeds improvedsignificantly
`over the 10 sessions, A(9, 81) = 4.57, < .0001. This is likely due to
`subjects’ getting accustomedto the software and the feel of the keyboard.
`One-handed typing mightalso have had an effect. There was no significant
`reduction in two-handed cumulative error rates over the 10 sessions, F(9,
`81) = 1.02, p> .05.
`The two-handedscoresjust given are the aggregate of the pretests and
`posttests. However,
`if we analyze them separately, we find that one-
`
`6. These rates differ slightly from those reported in Matias et al. (1993). Matias
`et al.'s rates wereartificially inflated due to a software error in the first several
`sessions. Note, as well, that the error-rate data underwent an arcsine transforma-
`tion before the analysis of variance. This technique stabilizes the variances when
`data are proportions (Winer, 1971, p. 400).
`
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`

`

`ONE-HANDED TOUCH TYPING
`
`13
`
`Figure 7 Mean key timesof the 11 most frequently occurring characters in Session 10.
`ONE-HANDED
`TWO-HANDED
`
`
`
`HB Non-flip = LeftHand_ill Right Hand@ Rip
`
`
`
`(msec) 1H Mean
`
`TIME
`
`2H Mean
`
`handed typing did affect two-handed performance, though not by much.
`The mean pretest speed over the 10 sessions droppedslightly from 63.8
`wpm to 62.1 wpm in the posttest. This drop wasstatistically significant,
`Fl, 9) = 8.64, p< .05, and weattribute it to interference and fatigue from
`40+ min of one-handed typing. Two-handed error rates were similarly
`affected: Cumulative errors rose from 2.79%to 4.10%, F{1, 9) = 11.6, p<
`.O1.
`
`Temporal Analysis
`
`Figure 7 shows the mean one-handed and two-handed key timesfor the
`11 most frequently occurring correctly typed characters in Session 10 in
`order of decreasing speed. Despite similarities in technique, we see that,
`from a temporal perspective, one-handed typing is very different from
`two-handed typing. In particular, the rank order of individual times is
`different. Although two-handed times seem fairly evenly distributed be-
`tween theleft and right hands, one-handed typing clearly favors nonflip-
`ped characters. The fastest one-handed times were for nonflipped
`characters, followed by the space character, with flipped characters being
`the slowest. If we consider these three classes of characters in context, we
`can see how this speed trend develops over the 10 sessions. Figures 8 and
`9 show the interkey timesbyclass for the 10 sessions.
`Figure 8 is as we would expect. Nonflipped characters were typed faster
`than flipped characters for all 10 sessions, and transitions were quickestif
`the preceding character was nonflipped. This is understandable given that
`
`MSFTEX. 1014
`Page 13 of 28
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`MSFT EX. 1014
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`

`

`14
`
`MATIAS, MACKENZIE, BUXTON
`
`Figure 8 Interkey times illustrating the degree of skill transfer/acquisition in flip and
`nonflip conditions.
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`flipped characters require one or two keystrokes, whereas nonflipped
`characters require only one. However, improvementover the 10 sessions
`was greatest for flipped characters. The mean interkeytimeforflip-to-flip
`transitions went from 1,126 msec in Session 1 to 374 msec in Session 10
`(less than one third of Session |
`time). Thus, initial skill transfer was
`greatest for nonflipped characters, but improvement was greatest for
`flipped characters. Figure 8 also highlights some key differences between
`one-handed and two-handed typing. Among expert two-handed typists,
`the fastest interkey times are those occurring between hands (Gentner,
`1983). In one-handed typing, the opposite is true—these transitions are the
`slowest (nonflip to flip) because they require an additional keystroke
`(depression of the spacebar) and are performed using a single hand.
`One-handed typing does not allow as much paralleling of actions as
`two-handed typing does. A two-handed typist can parallel movements
`between hands and among the fingers of each hand(eightfingers plus
`thumb); a one-handed typist can parallel only movements among the
`fingers of one hand(fourfingers plus thumb). Thus, the difference between
`one-handed and two-handed rates will likely be -greater for fast two-
`handed typists than for slower two-handed typists. As we shall see,thisis
`indeed the case.
`Figure 9 shows the mean interkey times for transitions involving the
`space character. There is a very interesting dynamic at play here, because
`space characters are issued later than the others—at the release of the key
`rather than whenit is pressed. The delayed space causes an imbalancing
`
`MSFT EX. 1014
`Page 14 of 28
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`MSFT EX. 1014
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`

`

`ONE-HANDED TOUCH TYPING
`
`15
`
`Figure 9. Effects of delayed space character on interkey times, Second slowest time in
`Session | is fastest time in Session 10.
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`effect that results in the second slowest transition (space to nonflip) in
`Session 1 becomingthefastest transition in Session 10.
`
`Error Analysis
`
`Theerror rates in this experiment were quite high compared to those
`reported by researchers testing other types of keyboards—namely,
`QWERTY(Grudin, 1983) and chord (Gopher & Raij, 1988). We believe
`this is due to the nature of the task being tested (viz., skill transfer).
`Half-QWERTY typing lendsitself very well to “educated guessing” by
`QWERTYtypists. The side effect is higher error rates. If an entirely new
`layout were being taught(as in previous studies), guessing would not be
`viable—key positions would have to be memorized in advance. This was
`not the case in our study. Subjects did not memorize the layout before
`starting the experiment. Theyrelied entirely on skill transfer—hence the
`higher rates. However, there was another factor that tended to inflate our
`error scores—the definition of an error.
`Our software displayed subjects’ typing beneath the input text. In
`addition to typing the text correctly, subjects had to type in synchroniza-
`tion with the input text already displayed. If they fell out of synchroniza-
`tion, each out-of-synchronization character was counted as an error,
`resulting in a higher reported error rate. This effect can be compensated
`for by grouping errors into chunks(i.e., counting only the first error when
`bursts of two or moreerrors occur in succession). As Figure 10a shows,this
`chunk error rate is lower than the cumulative rate previously cited. Fur-
`
`MSFTEX. 1014
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