The Journal 0/ Applied PsycholotyVol. 39, No S, 1955

Expected Locations of Digits and Letters on Ten-ButtonKeysets*

Mary Champion Lutz

Bell Telephone Laboratories, Murray Hill, New Jersey

and Alphonse ChapanisThe Johns Hopkins Iniversity

Although keysets are used on a great va-riety of machine devices—computers, codingdevices, and communications equipment—there appear to be few systematic studies con-cerned with the design factors that make key-sets easy or hard to use. The study reportedhere deals with one aspect of keyset design,viz., the locations of numbers and letters onindividual keys. In addition, we are con-cerned here with a particular class of keysets—ten-button sets used by long-distance tele-phone operators—but the results probably canbe generalized to other practical situations.

In making long-distance calls, telephoneoperators use a set of ten keys, arranged intwo vertical rows of five, with letters andnumbers on the keys as shown in Fig. 1.

To complete a call, the operator usuallykeys a letter-number combination which lookslike this:

815 RE 4-0267

The patterns of errors made by operators sug-gest that a different arrangement of the let-ters and numbers on the keys, or of the keysthemselves, might help to reduce errors As afirst step in the determination of the best ar-rangement of the keys and of the letters andnumbers on them, we decided to find out

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FIG 1 Arrangement of letters and numbers on atoll operator's keyset.

1 This study was done at the Bell Telephone Labo-ratories

where people say they would expect to find iletters and numbers on six different keysetconfigurations, only one of which resemblesthe present set (see Fig. 3). j

This is not an unusual approach in psy-chology. There are studies (1, 2) which showthat learning is more rapid and errors arefewer for tasks in which the stimuli and re-quired responses are in an "expected" relationthan in those where they are not. If peoplehave definite expectancies about the locationsof numbers and letters on keysets, this wouldprovide some rationale for the selection ofparticular keysets to be used in further op-erational tests.

The specific problem investigated had threeparts:

1. Where do people expect to find numberson each of six configurations of ten keys?

2. Where do people expect to find letterson each of six configurations of ten keys?

3. Where do people expect to find letterson each of six configurations of ten keys, givencertain preferred number arrangements al-ready on the keys?

MethodSubjects. The subjects for this experiment were

classified according to (a) age, (6) sex, (c) previ-ous experience on keysets such as appear on com-puting machines, typewriters, and musical instru-ments. Three hundred Ss were used, one hundredto answer each of the three questions, each one hun-dred chosen as in Table 1

Tat Materials. The test materials consisted ofbooklets containing circles arranged in each of thesix configurations shown in the top row of Fig. 3.Each configuration appeared on a separate page InPart I, a random arrangement of the digits 0 to 9was printed on the page opposite each configurationof circles In Parts II and III a random arrange-ment of the alphabet (except the letters Q and Z)was printed on the page opposite each configurationFor Part III only the booklets used configurationswith numbers already printed in the circles (seeFig 2) The numbering arrangements selected were

314

Digits and Letters on Ten-Button Keysets 315

Table 1Each of the Three Groups of 100 Subjects Was Com-

posed of Sampling Subgroups Containingthe Frequencies Shown Here

Men Women

Age 20-30 3(M0 Above 20-30 30-40 Above40 40

Naive 8Experienced 8

some of the most commonly chosen ones, as deter-mined in Part I

For all parts, each configuration of keys appearedfirst in a set of one hundred booklets either six orseven times. Also for each group of one hundredbooklets, there were equal, or as nearK equal as pos-sible, numbers of the sets of letters (or numbers)beginning with each letter (or number) Each num-ber or letter beginning a set appeared opposite eachconfiguration of keys an equal number of times

Procedure. The experimenter read to each S in-structions for filling out the booklets In Part I theinstructions told the subject to- (a) Put only onenumber on each circle (b) Place the first numberappearing in the list (opposite the circles) on acircle first, the second number appearing in the liston a circle next, etc (c) Place the numbers on thecircles in the order in which he would like to usethem if he had to key numbers all day long Theinstructions particularly stressed that the 5 shouldforget about any keyset arrangements which he ma>have seen in the past, and that the numbers (or let-ters) should be placed on the keys where he wouldexpect to find them, in the most natural arrange-ment, (d) Fill the first configuration of circles first,then go to the next one.

In Part II the instructions were the same as thosefor Part I except, (a) The instructions did notspecify the number of letters that the subject shouldplace on one circle (6) All instructions were givenin terms of letters, rather than numbers In PartIII the instructions were the same as those in Part IIexcept that the subjects were told that numbers al-ready had been placed on the keyset

Subjects were given unlimited time, and were al-lowed to erase previous selections if they changedtheir minds part way through a page.

Results

Part I. The most frequently chosen num-ber arrangements are shown in Fig. 3. Theoutstanding feature of the first choices is thatthe numbers are placed in order in horizontalrows, beginning with the top row. In the ar-rangements where there is an "extra" circle,the zero is placed in that circle. In the ar-rangements where there is no extra circle, the

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FIG 2 Configurations and number arrangementstested in Part III.

0 always follows the 9; it never precedesthe 1

The second most frequent kind of choicegenerally has numbers in vertical rows, in-creasing from top to bottom. Numberingplans which arrange the numbers in hori-zontal rows, starting with the bottom row,are next most common.

Chi-square tests show that: (a) There wereno statistically significant differences betweenthe age groups in numbering arrangementsfor any of the six configurations, (b) Therewere no statistically significant differences be-tween naive and experienced subjects in num-ber arrangements for any of the six configura-tions, (r) There were statistically significantdifferences (at .01 > p > .001) between menand women in numbering arrangements foreach of the four configurations containingthree rows of circles with one extra circle(the men chose the preferred arrangementsmore often than did the women); there wereno significant differences between the sexes onthe other two configurations of keys.

Part II. The most frequently chosen let-tering system agreed with the most commonnumbering system (see Fig. 3). i.e., the let-ters were placed in order in horizontal rowsbeginning with the top row. No matter whatthe configuration of keys, this lettering sys-tem was chosen by approximately one-thirdof the one hundred subjects. There were usu-

316 Mary Champion Lutz and Alphonse Chapanis

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each of the six configurations tested

ally two or three letters in order on each cir-cle. In the configurations where the "extra"circle is at the top, the first letters were placedin that circle; if the "extra" circle is at thebottom, the last letters were placed in thatcircle. If the "extra" circle is to one side ofthe others, letters were either placed in it fill-ing it out as if it were an ordinary part of thehorizontal row in which it lies, or the lastletters were placed in it.

There were no statistically significant dif-ferences in lettering arrangements on any ofthe six configurations between (a) men andwomen, (6) naive and experienced subjects,(c) subjects in the three age groups.

Part III. Three of the configurations usedin Part III (a, b, and c in Fig. 2) contain thenumber arrangements chosen most often bythe Part I group for each of the three majorclasses of keyset design (that is. two verticalrows of five keys, two horizontal rows of fivekeys, and a 3 X 3 configuration with an oddkey). For these three configurations, the

most frequently chosen lettering system wasthe same as found in Part II, i.e., the letterswere placed in order in horizontal rows, be-ginning with the top row. This lettering sys-tem was chosen for each arrangement by ap-proximately one-half of the total group.

There were no significant differences be-tween the choices of (a) men and women.(b) naive and experienced subjects, (c) thedifferent age groups.

The other three configurations used in PartIII (d, e, and / in Fig. 2) were selected be-cause they represent some numbering arrange-ments which were chosen with fairly high fre-quency in Part I but which are markedlydifferent from the most commonly selectedones. For these three configurations, thegroup was almost equally divided between alettering system which followed the numberarrangement on the keys (putting two orthree letters in order on each key) and thelettering system which appeared most fre-quently on the other configurations in Part

Digits and Letters on Ten-Button Keysets 317

- Ill (in order in horizontal rows, beginning" with the top row). Each of these alternative

systems was chosen for each configuration byapproximately one-third of the group.

According to chi-square tests, there were no- significant differences between lettering ar-- rangements chosen by (a) men and women,

(b) naive and experienced subjects, (c) dif-ferent age groups of subjects.

An incidental finding was that no subjectarranged the numbers or the letters as theyare now arranged on the keyset.

Discussion

The most obvious finding of this study isthat people arrange numbers and letters inthe order in which they normally read. Thisis true for all configurations of keys, for bothnumbers and letters, and for both experiencedand inexperienced subjects. Of the severalcalculating devices we have been able to lookat, only one (the IBM card punch) uses anarrangement which is highly preferred in thisstudy. It resembles the pattern illustrated asthe fourth from the left in the top row ofFig. 3. Two other calculators have keysetsresembling the third from the left in thesecond row of Fig. 3. These are the multi-plier keys on the Friden calculator and thekeyset of the Remington Rand adding ma-chine. Most other calculators have their keysreading upward in vertical rows of ten. Inall of these, the "0" customarily is placed be-low the " 1 , " a placement which was seldomfound in our tests.

Of course, we have no assurance that thesedifferences between calculator keysets are ofany practical importance. In fact, our studyof expectancies can be considered only a firststep toward finding the keyset which wouldgive the fewest errors and shortest keyingtimes. The next logical step would be totest some most-frequently chosen letter andnumber arrangements against some of theleast-frequently chosen ones in an actual key-ing situation.

A final word is in order concerning thegreater consistency the men showed in choos-ing number arrangements. We believe thatthis may reflect a difference in experience be-tween the two groups which was not takeninto account in selecting our samples Virtu-

ally all of the men had technical training andwere either engineers or their assistants, whilemost of the women were typists, clerical help,or maintenance people unexposed to any sortof technical training. Thus even our "inex-perienced1' men undoubtedly had greater fa-miliarity with number systems and the ar-rangement of numbers on graphs and otherdisplays than the corresponding group ofwomen.

Summary and Conclusions

This experiment attempted to find outwhere people expect to find letters and num-bers on each of six configurations of ten keyseach. Three hundred Ss, stratified accordingto age, sex, and previous experience on key-sets, were asked to write on diagrams of key-sets either numbers or letters in the arrange-ments that they felt were most natural. Ourresults show:

1. People expect to find numbers on key-sets arranged in left-to-right order in hori-zontal rows starting with the top row, for allof the six configurations of keys.

2. People expect to find letters on the key-set arranged in left-to-right order, with twoor three letters in order on each key, in hori-zontal rows, starting with the top row, for allof the six configurations of keys tested.

3. With numbers already on the keyset:(a) People expect to find the letters arrangedin horizontal rows, beginning with the toprow, for those patterns in which the numbersare arranged thaf way. (b) When the num-bers are arranged in patterns not having num-bers in order in horizontal rows (beginningwith the top row), people are equally dividedbetween lettering arrangements following thenumbering pattern and lettering as in (a)above even though this conflicts with thenumbering arrangement.

Received September 23, 1954.

References1. Gibbs, C. B Transfer of training and skill as-

sumptions in tracking tasks. Medical Re-search Council, Applied Psychology ResearchUnit, Cambridge Rep No A P U. 127/SO,September 1950 Pp 18

2. Mitchell, M. J H , & Vince, M A. The directionof movement of machine controls Quart J.exp. Psychol., 1951, 3, 24-35.