Class ScanningKeyboardExperiment

java.lang.Object

ScanningKeyboardExperiment

public class ScanningKeyboardExperiment
extends java.lang.Object

ScanningKeyboardExperiment

Summary

• Experiment software for text entry using a scanning keyboard

• Only the Spacebar is used for input

• Several keyboard layouts are supported, some including word prediction and completion

• A custom keyboard can be defined and read from a text file

Related References

• "Modeling Text Input for Single-switch Scanning", by MacKenzie (ICCHP 2012). Describes modeling, as the title suggests, and also presents and examines the metric "scansteps per character" (SPC).

Running the Experiment Software

Click here for instructions on launching/running the application.

Setup Parameters

Upon launching, the program presents a setup dialog:

The default parameter settings are read from a configuration file called ScanningKeyboardExperiment.cfg. This file is created automatically when the application is launched for the first time. The default parameter settings may be changed through the setup dialog. The setup parameters are as follows:

Parameter	Description
Participant code	Identifies the current participant. This is used in forming the names for the output data files. Also, the sd2 output data file includes a column with the participant code.
Condition code	An arbitrary code used to associate a test condition with this invocation. This parameter might be useful if the software is used in an experiment where a condition is not inherently part of the application (e.g., Gender → male, female, Input Device → gamepad, keyboard). The condition code is used in forming the name for the output data file. Also, the sd2 output data file contains a column with the condition code.
Session code	Identifies the session. Useful if testing proceeds over multiple sessions to gauge the progression of learning. Note: The setup dialog does not include an entry for "Block code". The block code is generated automatically by the software.
Number of phrases	Specifies the number of phrases presented to the participant in the current block.
Scanning interval	The time in milliseconds for each scan step. Applies both for row scanning and column scanning.
Scan delay	A delay time in milliseconds that is inserted each time the Spacebar key is pressed. Applies both when Spacebar is pressed during row scanning (to switch to column scanning) and when Spacebar is pressed during column scanning (to select a character or word and then revert to row scanning). The added delay gives the user a little extra time to adjust to the new scanning mode.
Phrases file	Specifies a file containing phrases of text to be presented to participants for entry. Phrases are drawn from the file at random. Typically, phrases2.txt is used. This is the phrase set published by MacKenzie and Soukoreff in 2003 (click here).
Show presented text during input	A checkbox item that determines whether or not the presented text is visible during entry of a phrase. Either way, the text phrase appears at the beginning of a trial. If this option is unchecked, the phrase will disappear when the first keystroke is entered.
Audio on	If on, audible "clicks" are heard during row and column scan steps and when the Spacebar is pressed.
Keyboard	A drop-down list to select the scanning keyboard for the current invocation. The options currently supported are as follows: (click to enlarge) Qwerty Qwerty_WP ABC1 ABC2 ABC ABC_WP Optimized Optimized_WP Custom (select below) Note: The optimized layout above is one of many such designs aimded at reducing the average number of scan steps required for each character of text produced. Consult the reference at the top of this API for details on this and other optimized layouts for scanning keyboards.
Custom keyboard	If the "Custom" option is chosen above, this button is clicked to launch a file chooser to select a text file containing the definition of a custom keyboard. Each key in a scanning keyboard is defined by seven parameters: Symbol — the text that appears on the key (Exception: "WORD" is used if the key is used to present candidate words for keyboards using word prediction and completion) rowIdx — the row index for the corresponding key colIdx — the column index for the corresponding key x — the relative x position of the key y — the relative y position of the key width — the relative width of the key height — the relative height of the key Note: The last four values above are multiplied by default key width and key height constants that are embedded in the app. Click here to see an example custom keyboard. As a learning aide, this custom keyboard is the same as the Qwerty_WP keyboard that appears in the Keyboard drop-down list.
Keyboard scale	Selects the scale of the keyboard relative to the default key width and key height constants embedded in the application.

Program Operation

Upon clicking OK in the setup dialog, the application launches:

A phrase is drawn at random from the specified phrases file and presented for input. After pressing the Spacebar, scanning begins, row by row. The timing of user input begins when scanning begins (after the initial press of the Spacebar key).

When the row containing the desired letter is highlighted (below, left), the user presses the Spacebar to begin scanning within the row. This begins column scanning. When the key bearing the desired letter is highlighted (below, center), the user presses the Spacebar again to select the letter. The letter is added to the transcribed text phrase and scanning begins anew (below, right). Note that it takes two presses of the Spacebar to enter each text character.

After entering the complete phrase, the user inputs "Enter" (by pressing the Spacebar when the Enter key is highlighted). A pop dialog appears, showing the presented and transcribed text phrases and some user performance measures. Below is an example.

The program terminates after entry of the last phrase in a block.

Some of the keyboards (See the setup parameter for "Keyboard", above) include word prediction and completion. In this case, a series of keys are used to display candidate words as entry proceeds. The candidates are the most likely words matching the current word stem, based on an embedded word-frequency list, or dictionary. The dictionary contains about 10,000 words. Note that at the beginning of a phrase and between words the candidates are simply the most common words in English (since the word stem is empty).

Output data files

At the end of each block, data are written to two "summary data" (sd) files. The "sd1" file contains data on a per-character basis, one line per character. Each line contains three values: (i) the character, command, or word entered, (ii) the timestamp in milliseconds, and (iii) the number of scan steps. The "sd2" file contains data on a per-phrase basis, one line per phrase. Example data files follow:

• sd1 example
• sd2 example

The data are full-precision, comma-delimited. Importing into a spreadsheet application provides a convenient method to examine the data and do follow-on analyses. Below is an example of how the data in the sd2 file might look after inporting into Microsoft Excel: (click to enlarge)

Several user performance measures in the sd2 file are potentially useful as dependent variables in a user study. Speed (wpm) and Error Rate (%) are well known in research on text entry methods. The metric called SPC (scan steps per character) is computed as

scan_steps / number_of_characters_in_transcribed_text

The numerator is the actual number of scan steps logged during entry of the current phrase. SPC is the scanning-keyboard equivalent of KSPC (keystrokes per character), which is commonly used for keyboards using physical keys for input.

Efficiency is computed as

scan_steps_min / scan_steps x 100

Here, the numerator is the minimum number of scan steps possible for the current text phrase. If Efficiency = 100%, the phrase was inputted with each character or word entered correctly and at the earliest opportunity (i.e., with no errors that were corrected and with no missed opportunities). If Efficiency < 100%, the user either made one or more errors that were corrected or missed some opportunities to enter the desired character or word at the earliest opportunity. Note that the Efficiency measure is only meaningful if the transcribed text is error free.

Additional measures include Presses_of_Bksp, Presses_of_Word_Delete, Row_wrap_arounds, and Col_wrap_arounds. Presses_of_Bksp and Presses_of_Word_Delete are the number of times the named key was pressed during input of the current phrase. Obviously, Bksp is used to correct errors. Word_Delete (if present) is pressed to delete the last word entered. This is particularly useful with keyboards using word prediction and word completion. Having entered the wrong word, the error is more quickly corrected using the Word_Delete key rather using multiple presses of the Bksp key.

The Row_wrap_arounds and Col_wrap_arounds measures indicate the number of times scanning wrapped around, either during row scanning or column scanning, respectively. When scanning wraps around, it means the user missed an opportunity, either to select a row or to select a column (character, word, or command). Missed opportunities indicate inefficient input and may occur because scanning is too fast for the user to make a selection, given the previous selection.

Actual output files use "ScanningKeyboardExperiment" as the base filename. This is followed by the participant code, the condition code, the keyboard code, the session code, and the block code, for example, ScanningKeyboardExperiment-P01-C01-ABC_WP-S01-B01.sd1.

Miscellaneous

When using this program in an experiment, it is a good idea to terminate all other applications and disable the system's network connection. This will maintain the integrity of the data collected and ensure that the program runs without hesitations.

Author:

Scott MacKenzie, 2016-2022

Constructor Summary

Constructors

Constructor and Description
ScanningKeyboardExperiment()

Method Summary

Modifier and Type	Method and Description
static void	main(java.lang.String[] args)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ScanningKeyboardExperiment

public ScanningKeyboardExperiment()

Method Detail

main

public static void main(java.lang.String[] args)
                 throws java.io.IOException

Throws:

java.io.IOException