Long-term Speed and Accuracy of Morse code vs. Head-pointer Interface for Text Generation

Denis K. Anson, MS, OTR/L, Melinda Glodek, OTS, Richard M. Peiffer, OTS, Cory G. Rubino, OTS,
Patrick T. Schwartz, OTS
College Misericordia
301 Lake St.
Dallas, PA 18612

Abstract

The purpose of this study was to determine which of two alternative computer input systems produces a greater rate of output once proficiency is reached. Four participants had prior experience with Morse code, while none had experience with head-pointers and on-screen keyboards. Over a short-term assessment, the combination of on-screen keyboard and head-pointer provides input rates that are faster than those achieved by Morse code. However, individuals who have more experience with Morse code were able to type faster with Morse code than with the on-screen keyboard.

Statement of the Problem

Disabilities such as spinal cord injury, MS and Cerebral Palsy can limit an individual's ability to control his/her hands, but spare the ability to move his/her head and face (1). For the person with intact movement above the shoulders, but limited movement distally, there are few methods of functional computer control. Among these are Morse code input and the combination of head pointing devices and on-screen keyboards. Morse code input, according to long-term users, eventually becomes automatic, but requires significant training to achieve proficiency. The level of control offered by head-pointers is closely comparable to that of a standard mouse; however, limited endurance and restricted range of motion of the head and neck may limit their use (2).

According to the Human Interface Assessment Model (HIA), the role of assistive technology is to bridge the gap between the abilities of the individual and the demands of the task (3). Since different access methods make different demands on the person with a disability, the therapist must carefully match the functional ability of the person to the enabling device.

Most clinical decisions between different access technologies must be based on short-term clinical trials. The purpose of this study is to determine which of two alternative computer input systems, Morse code or head-pointing with an on-screen keyboard, produces a greater rate of output once proficiency is reached.

While head-pointing and on-screen keyboards are commonly accepted, Morse code is rarely used by people with disabilities. Because clinicians should recommend the system that will provide the best chance for functional performance, objective information on the relative utility of these two input methods is important.

Our research hypothesis is that, on initial training, the headpointing system will allow faster typing, but over time, Morse code typing will be faster. Our second hypothesis is that there will not be a significant difference in accuracy between the input devices.

Methodology

Design

A single-subject, successive intervention design was used to compare the typing speed and accuracy of a head pointing system combined with an on-screen keyboard and Morse code text input. In order to provide a consistent task, all typing in this study consisted of copying from provided text. Since we do not feel that these two input methods are markedly different in cognitive demands, we feel that the relative merits of the two devices would not change during composition tasks.

Typing speed was indicated by the number of words typed during twenty-minute trials. An error was considered to be any discrepancy between the participant's work and the original source

Percent accuracy was calculated using the formula: Percentage accuracy = (1-(total errors for passage/total words typed))*100. This results in an accuracy value that is independent of typing speed.

Performance plateau was achieved when the participant produced three trials with typing speeds within 7 percent of each (9).

Participants

The participants for this study were eight (5 male and 3 female) able-bodied individuals from 19 to 59 years old with a mean age of 34.6 years. Half of the participants selected for this study were long-term users of Morse code recruited from a local ham-radio club although none were familiar with sip and puff input. Additionally, none of participants had prior experience with head pointing. This mix was used to evaluate both the short and long term performance for Morse input.

None of the research participants were physically disabled. The individuals for whom Morse code and headpointing are both viable input methods have normal or nearly normal head movement and oral-motor control. The able-bodied experimental participants are, therefore, reasonable analogues to the disabled individuals they are representing, in terms of head and intra-oral control.

Procedure

Two personal computers were used in the study. Text was typed into Microsoft Word 2000¹, which was also used to evaluate the speed and accuracy of typing. Morse code input was through the Darci Card Morse code interface device² connected to a sip and puff switch³. Headpointing input was performed using the HeadMaster Plus⁴ in conjunction with ScreenDoors 2000⁵ on-screen keyboard program.

The source was was divided into segments of approximately 500 words (each segment ended at the end of a paragraph which contained the 500th word.

A balanced-order assignment was used to determine the initial input device for each of the participants in order to control for possible order effects. During the Morse code sessions a chart of Morse code symbols and the source document were mounted to either side of the monitor at a height approximately equal to the screen. Each typing trial was 20 minutes long.

Table 1. Speed and accuracy at Mastery of Morse code and Head-Pointing
	Subject Number	Morse Code		Head-pointer
		Speed	Accuracy	Speed	Accuracy
Naïve Morse code Users	221	5.7	96%	6.2	92%
	426	2.2	96%	4.4	98%
	507	4.9	95%	5	96%
	738	4.1	100%	4.6	98%
Experienced Morse code Users	325	5.2	96%	4.7	89%
	359	5.3	95%	4.4	95%
	374	6.4	98%	4.3	93%
	821	4.9	97%	3.5	96%

Results

Figure 1. Comparison of Typing for a Morse Naïve typist (Click image for larger view) d

All four participants who had no prior experience with either input method were able to type faster with the combination of head-pointing and on-screen keyboard than with Morse code. Figure 1 illustrates the typing speed of a typical participant with no experience on either input method. The non-experienced user reached plateau in fewer trials with the head pointer than with the Morse code device, and achieved a typing speed faster than that obtained with Morse code.

All four participants with Morse code experience reached a plateau at a greater rate with the Morse code device than with the head-pointer. Figure 2 illustrates the typing of a Morse experienced participant who reached a plateau in typing speed at a greater rate with the Morse code device than with head pointing. The participant reached plateau with the head pointer in fewer trials than the Morse code device but at a lower speed. However, the participant continued to demonstrate improvement in Morse code input upon reaching the standard for plateau.

**Figure 2. Comparison of Typing for a Morse Experienced Typist** (Click image for larger view) d

Accuracy of typing trials for all participants was visually compared in Table-1 for differences between the two input methods. There were no systematic differences in accuracy between experienced and non-experienced participants or between input samples produced by the two devices.

Discussion

Frequently, the decision as to which input device is best suited for the client is determined by a short-term assessment of speed and ease of use. Head pointing systems, given their low demands for training, offer fair performance with minimal training. The results of this study show that, over the short term, the client who has no experience with either input device is likely to demonstrate faster typing speeds using head-pointing than with Morse code.

The long-term benefit of Morse code is more clearly evident in the data collected from experienced users of Morse code. These subjects performed significantly faster with the Morse code input both initially as well as long-term. This result indicates that choosing the headpointer based on a few trials may be a premature decision. It is likely that, with experience, the naïve users would demonstrate comparable results.

Conclusion

When choosing an input method for a client, head pointing, in most cases, will allow for faster text input over the short-term because less learning is required. However, the client will not be using the selected input device only over the period of evaluation. For the client, this decision will affect performance over a period of many years. This study indicates that, given time, Morse code is likely to provide faster text generation than head-pointers.

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Microsoft Word. Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399. USA

Dacri Card. The Darci Institute of Rehabilitation Engineering, 810 W. Shepard Lane, Farmington, Utah 84025. Phone: 801-451-9191, Fax: 801-451-9393

Enabling Devices and Toys for Special Children, Inc. 385 Warburton Ave. Hastings-on-Hudson, NY 10706. Phone: (914) 478-0960

HeadMaster Pro, Prentke Romich Company, 1022 Heyl Road, Wooster, OH 44691, 1-800-262-1984, http://www.prentrom.com

Madentec, Ltd., 9935 - 29A Avenue, Edmonton, Alberta Canada T6N 1A9, Phone: (780) 450-8926, Fax: (780) 988-6182, Toll Free: (877) 623-3682, http://www.madentec.com.