Continuous Performance Test

Transcription

1 Continuous Performance Test Sanzen Neuropsychological Assessment Tests Figure 1 1

2 CONTENTS 1) SANZEN Neuropsychological Assessment Tests ) Introduction to the Continuous Performance Test ) Registering Your New Test..15 4) Executing a Continuous Performance Test ) Analysis of Results 18 6) Creating and Editing a Continuous Performance Test 21 7) Normative Data ) References..52 2

3 Continuous Performance Test The Sanzen Neuropsychological Assessment Tests implementation of the Continuous Performance Test (CPT) allows for considerable flexibility in test design. Targets, nontargets and warnings can be presented either as visual or auditory stimuli. When presented as visual stimuli they can appear in any one of multiple locations on the screen and can be presented in different colors as alpha/numeric characters, icons or words. When presented as auditory stimuli they can be presented as tones (A below middle C to G# above middle C) to either the right, left or both ears, or they can be presented as spoken words. Both the stimulus and the inter-stimulus intervals can be set. Participant response input can, at the test authors discretion, be from the keyboard, mouse, keypad or gamepad. A capability for designating response exclusion zones is provided. Extensive capability for providing either visual or auditory distraction is provided. As the CPT can be conceptualized as a signal detection task a payoff matrix can be defined and used to display a running score of participant performance during testing. Block-by-block analysis of responding includes response counts, response latencies, the standard deviation of those latencies, d and β. Additionally, blocks can be grouped for summary analysis. Vigilance tasks similar to tasks now collectively referred to as continuous performance tests were first developed in the 1940s to assess human performance capabilities of an observer on monotonous tasks requiring sustained monitoring for any changes in a stimulus field. Perhaps the best known of these early tasks was the clock test developed by Mackworth (1948). In that task individuals were required to monitor for extended periods of time (up to two hours) the saccadic sweep of a second hand around the face of a blank clock, responding whenever the hand jumped more than one saccade. This basic paradigm was first used by Rosvold, Mirsky, Sarason, Bransome and Beck (1956) as potentially a new instrument for the study of brain damage in human subjects. In this initial study two tasks were used. In both tasks letters were present at a rate of one stimulus item every.92 seconds for approximately.23 seconds. In the first task the subject was instructed to press a response key every time they saw an X, but not respond to any other letter. In the second task they were instructed to press the response key every time they saw an X but only if that X was preceded by an A. They looked at three groups, defectives, children and adults, and within each of those groups two sub-groups, brain-damaged and non-brain-damaged. Only one condition, Adults on the X task, failed to show a significant difference between brain-damaged and nonbrain-damaged subjects. They concluded that the CPT is sufficiently reliable and yields sufficiently large differences between subgroups to suggest that it might ultimately prove 3

4 useful as a clinical instrument for the diagnosis of brain damage. For the most part all CPTs in use today follow some variation of this basic paradigm. Registering Your New Test When first loaded, whether from an online download or a physical disk, execution of the installed program will prompt for the registration of the newly installed SANZEN software. This prompt will continue to appear each time the program is run until the registration procedure is completed. If the computer on which the software has been installed is connected to the Internet, the software can be automatically registered by providing the information requested (i.e., the name of the purchaser and the purchaser s address) and clicking the Register button. A Product Key Code will be sent to the address provided within two working days. After receipt of the Product Key Code, enter it in the provided fields and click the Enter button to complete the registration procedure. (Note: Each time a program is installed and executed for the first time it is issued a new Serial Number so each of the three allowed installations will have its own unique combination of Serial Number and Product Key Code.) Be sure to note both the Serial Number and Product Registration Key as they may be required in subsequent interactions with SANZEN Neuropsychological Assessment Tests. Once registration is completed the Product Registration screen will not appear again. Executing a Continuous Performance Test Select a test from the Select Test to Execute pulldown list located in the upper right corner or the Welcome screen (Figure 1). A Select Participant dialog will be displayed (See Figure 2). Select the name of the participant to be tested from the Select a Participant pull-down list. (Note: If the participant s name is not in the list you will need to return to the Sanzen Menu screen and enter them into the Participant Database.Click the Cancel button to do this.) You can at this point change the Tester Name or simply accept the displayed name (the name of the currently logged in user). Click the Run Test button and the test will begin execution. A test can be terminated at any time by pressing [Ctrl]X. The recorded data for the test will not be saved. 4

5 Figure 2 Analysis of Results Figure 3 shows a data analysis screen; the left panel displays Summary data for the test, while the right panel shows the event record for this test and test selection xxx. Select a test for analysis by first selecting the participant whose test data is to analyzed from the Select a Participant pull-down list. All CP tests the participant has taken will be displayed in the Tests Taken list. Select a test for analysis from that list by clicking on the test. The summary analysis will be calculated. Note: During that calculation you may be warned that on some trials that the relative frequency a hit has exceeded.9998 or the relative frequency of a false alarm was less than The Z score table used in calculating d has been restricted to ±3.49 and cannot handle relative frequencies more extreme than.0002 and This restriction will limit d to a maximum of Summary Table Organization Columns: The left most columns of the summary table, labeled 1 to X contain the analyzed data for each of the defined blocks. The right most columns of the table labeled Group-1 through Group-x contain summary data for blocks that are grouped together for analysis because of some shared characteristic. For example, in the displayed analysis blocks one and two both have the same relative frequency of 5

6 target,.2, and have been grouped together as Group-1for analysis. Blocks three and four have a relative frequency of target of.8 and are grouped as Group-2. Trials can be assigned to a particular group or groups during test design (See the section on test design). Rows: Figure 3 [T]argets The number of target presentations in the block or group. [W]arnings The number of warning presentations in the block or group. [~T]argets The number on non-target presentations in the block or group T / (T + W + ~T) The relative frequency of Target in the block or group. Hit Count The number of Hits (correct responses to a target) for the block or group. Mean Hit Latency (msecs.) The mean time to respond following the presentation of a target for a block or group. Hit Latency SD The standard deviation of Hit Latencies for a block or group. 6

7 Miss Count The number of target presentations for which there was not response for a block or group. Correct Rejection Count the number of Targets plus Warnings where the participant correctly did not respond for the block or group. False Alarm Count The number of times a participant incorrectly responded to a target or warning for a block or group. Mean False Alarm Latency (msecs.) The mean time to incorrectly respond following the presentation of non-target or Warning for a block or group. FA Latency SD The standard deviation of False Alarm Latencies for a block or group. Excess Response Count The number or response in excess of the Hit count plus the False Alarm count for a block or group. These responses are not used in calculating responses (i.e. Hits and False Alarms) but are included as a possible measure of extraneous behavior. d An index of observer sensitivity for a block or group. β An index of observer decision criteria for the block or group. Event Recorder: The Event Recorder contains a continuous record of all salient events occurring during the course of the test. It allows investigators access to that record should they wish to perform analysis not provided in the summary table. The first column contains the ordinal position of an event; the second column, the event; the third column, arguments elaborating the event and the fourth column a time-stamp indicating when in milliseconds since the recorder was started that the event was detected by the computer. So in the results shown in Figure 3 event 0 was a Start Test event, the argument specifies the date and time the test was started and the Time Stamp indicates that the event 0 milliseconds after the Event Recorder was started. Nine milliseconds later event 1, a Start Block event occurred. The argument contains information describing properties of the block. Event 2 was a StimulusOn event and the argument indicates that it was the presentation Token 1, a Target. This event occurred almost 26 seconds after event 1 (presumably the participant was reading the instructions presented at the beginning of a block. Slightly more than 500 milliseconds later event 3, Response, occurred affirming the presence of a target. 7

8 Design Test Sanzen Neuropsychological Assessment Tests implementation of the Continuous Performance Test (CPT) is sufficiently flexible to allow the user to design tests similar to any CPT currently in use, as well as allowing them to extend test design well beyond those tests. Its setup screen can at first be daunting. Figure X on the next page shows a setup screen for the fourth block of our Faces test. Begin by either selecting a previously defined test for editing from the Select Test for Editing pull-down list located in the Test Definition display box. Doing so will display the test and if a block has been previously defined for that test the first block will be displayed in the Block Definition display box. Or if creating a new test, click the New Test button. A small window will open requesting a name for the new test. Type the name of the new test in the name field provided. The only restriction on test names is that the new name cannot be same as the name of an existing test. Once the new test name has been entered click the Ok button to create the new test. From here on the procedures for either editing a test or creating a new one are essentially the same. There are several test parameters that may need to be set. (Whenever a new test is create those parameters are assigned default values, which at the test author s discretion can be either accepted or changed.) Test Instructions Clicking the Test Instructions button opens the instruction editor allowing the author to enter a set of instructions for the test. If instructions have been provided they will be displayed (and if Use Audio has been checked read to the participant) at the beginning of the test. Screen Color The background color of the testing screen can be set by clicking the box labeled Select Test Screen Color. Doing so will open a color dialog allowing the test author to select a color for the test screen. Use Audio If this box is checked the computer will read to the participant all instructions and test messages (Assuming audio capabilities are available on the testing computer). Thank You Message The Thank You message can be altered to meet the needs of the linguist community in which the test is going to be administered. Use Icons If this box has been checked then a smiley face will be substituted for the Thank You Message text. If Use Audio has been checked the message Thank You Message box will still be read to the participant. Once the test has been appropriately defined, click the Save Test button to save the test. 8

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10 Block Definition The procedure for editing an existing block or creating a new block are essential the same. Edit an existing block by navigating to the block to be edited using the Block Selector. Clicking one of the four buttons in selector will take you to the first [ ], previous [ ], next [ ] or last [ ] block of the test. Create a new block by clicking the Add New Block button. Practice If the block is a practice block click the Practice box. (Practice blocks are excluded from the summary data analysis.) Group A block can also be assigned Group designations allowing for blocks with similar parameters, relative frequency of target for example, to be grouped together for a summary analysis of all groups sharing that parameter. As block data may need to be grouped in more than one way a block may be assigned to several groups. So, for example, the fourth trial of the Faces test has been assigned to Group 1 as has the fifth block (both of these blocks share a.25 relative frequency of target). The sixth and seventh block have been assigned to Group 2 (both of these blocks share a.75 frequency of target). When an analysis is done of a participants test result, not only will a block-by-block analysis of the results be done, but also a group-by-group analysis. Enter in the group field a list of integers from 1 to 9 indicating a blocks group assignment. Assign the block a 0 for no group designation. Token Definition Token definition is central to the development of a Sanzen CPT. The first step in creating a set of token definitions is to determine the font to be used in constructing the tokens. Select a font by clicking the Select Font (..) button to open the font selector dialog and select a font. Any font resident on your computer including dingbats can be used. In the displayed example we have used the Microsoft dingbat Wingdings for our Faces test. (Literally thousands of fonts are available on the web if the fonts resident on your computer do not contain dingbats or a character set suitable for your use.) Create a new token by clicking the first available blank cell in the column labeled Token and then either type the characters for the new token into the cell (you may have tokens containing up to six characters), or alternatively, if you are using dingbats, open the character map by double clicking on the cell and selecting the required dingbat from those displayed in the map. Entering the token will assign it a unique Id (shown in the column labeled Id) and a set of default values. Each of these values can be changed to meet the needs of the test. 10

11 Color A token s display color can be assigned any one of several colors specified in the Color pull-down list. In the faces example we are using Orange and Magenta. Tone If the token is going to have a tone component choose any one of 12 tone ranging from A below middle C to G# above middle C from the Tone pull-down list. Mode Specify the presentation mode for the token from the Mode pull-down list. There are nine modes of token presentation: Visual The token defined in the Token column is displayed. Voice The computer speaks the token defined in the Token column but will not display it. So, for example if the word Red was in the Token column the computer would say the word red. Tone (B) The tone specified in the Tone column is sounded in both the right and left ear. There is no visual display. Tone (L) The tone specified in the Tone column is sounded in the left ear only. There is no visual display. Tone (R) The tone specified in the Tone column is sounded in the right ear only. There is no visual display. Visual/Voice The token defined in the Token column is both displayed and spoken by the computer. So, for example if the Token column contained the number 7 the character 7 is displayed and the computer says seven. Visual/Tone (B) The token defined in the Token column is displayed and the Tone specified in the Tone column is sounded in both the right and left ear. Visual/Tone (L) The token defined in the Token column is displayed and the Tone specified in the Tone column is sounded in the left ear only. Visual/Tone (R) The token defined in the Token column is displayed and the Tone specified in the Tone column is sounded in the right ear only. Location The token can be displayed in any one of five positions in the display space Center, Top, Bottom, Left or Right. Type The token can be any one of three types, a target (Target), a non-target (~Target) or a warning (Warning). Tokens must be defined individually for each condition in the block. In many cases only two tokens need defining, one for target and one for non-target. In the cases of Faces a target could appear in any one of five display locations, so five target tokens differing 11

12 only in their display location needed to be defined. Five non-targets differing only in their display location also needed to be defined. Presentation List The Presentation List is displayed at the right edge of the Token Definitions display box. It contains a list of token ids as displayed in the Id column of the token definition grid. So, for example, in the displayed Block Definition token 5 is displayed first followed by token 4 and so on. There are two ways to define a presentation list. Manually A token can be added to the end of the Presentation List by left double clicking the row header (the blank column immediately to the left of the Id column of the token definition grid) of the row containing the definition of the required token. Alternatively Right clicking on the Presentation List will open the list edit menu. Clicking Add on that menu will add the selected token to the end of the list. Four other edit options are available on that menu. (Note: Right clicking on a row in the Presentation List selects that row.) Replace will replace the token currently selected in the presentation list with the token currently selected in the token definition grid. (Selecting a token from the token definition grid is done by clicking the row header for the required token. The selected the currently selected rows in both the token definition grid and the presentation list are indicated by a blue background.) Insert will insert the token currently selected in the token definition grid immediately before the token currently selected in the presentation list. Delete will delete the token currently selected in the presentation list. Clear clears the entire presentation list and allows you to start over. Manual construction of the presentation list is the preferred way of generating the list when precise control over the order of token presentation is required. Auto Create Manually creating presentation lists for blocks is a tedious process, perhaps even more tedious than actually taking a CPT. However, blocks can be created automatically. Clicking the Auto Create List button will open a dialog (Figure 5) which has a pull-down list containing the Id number of all the defined tokens. Directly below that pull- down list is a space to assign the number of instances of the token represented by that id required in the presentation list. Select a token id from the token id pull-down list, assign it an instance count and click the arrow button immediately to the right of the instance count box. The token id and its instance count will be added to 12

13 the list immediately to the right of the arrow button or if the token id already appears in the list its instance count will be updated. A token id-instance count pairing can be removed from that list by double clicking on the pairing. Once all of the id-instance pairing have been assigned, clicking the Ok button in that dialog will generate a list of randomly distribute tokens. This feature cannot be used if Warning tokens are required, or at least the generated list will need to be manually fixed to insure that all Target tokens are properly preceded by a Warning token. Auto Create is of particular use when the Copy Block -- Paste Block feature is used as that feature creates an exact replica of the copied block in the pasted block and Auto Create allows for the easy generation of token presentation lists with different orders or counts.. Response Mode Figure 5 Any one of four response modes can be specified for participant responding. Keyboard Tapping the spacebar is counted as a response. Mouse Depressing the left mouse button is counted as a response. Game Pad Pressing the green A button on a conventional game pad is counted as a response. (We use two varieties of game pads for our testing, either a Microsoft Sidewinder or a Logitech F310 gamepad.) Number Pad Pressing the 0 key of a number pad is counted as a response. 13

14 Response Exclusion Zone allows for excluding responses as legitimate during certain periods of the presentation cycle although responses during those periods are captured and counted as Excess responses. The Pre-Stimulus period specifies the period prior to the presentation of a token in which a response will not be accepted. Presumably responses that occur during this time are anticipatory and not actually legitimate responses to a token. In the displayed example that time has been set to 50 msec. The Stimulus exclusion zone begins with the onset of the token display and remains in effect for the specified duration, in the example, 150 msec. This exclusion zone precludes any response that could not be a legitimate response to the presented token, as legitimate latencies are typically in the 350 to 450 msec. range. Token Display Display Duration specifies the amount of time a token presented visually will be displayed. Alternatively, if the token is presented as a tone then Display duration specifies the length of time the tone will be sounded. Cycle Duration specifies the amount of time between the onset of the n th token and the n+1 token. Range specifies the variability of the cycle duration. Setting this value to something other than 0 will generate a constant probability distribution with a minimum value equal to the Cycle Duration minus the Range, a maximum value equal to the Cycle Duration plus the Range and a mean equal to the Cycle Duration. The Range may not be greater than the Cycle Duration. Token Size Tokens can be any one of three sizes Small (26 point), Medium (72 point) or Large (120 point). Small tokens are suitable for displaying words of up to ten characters in length. Display Size The field containing the five token display locations can be set to any one of three sizes, Small, Medium or Large. If random distraction (more about this later) is used then the Display Size must be set to Large. Display On Always If this box is checked then the token display space is constantly visible. If it is not checked the display space will be visible only when a token is being displayed. Select Display Space Color allows for the setting of the display space color. This color can be set independently of the screen color. 14

15 Display Token Box Boarders Checking these boxes turns on a boarder around the specified token display location. Distractor Definition Extraneous stimuli can be presented during the course of token presentation. Type Distractor stimuli can be presented in several ways. Surround Selecting this option causes the distractor to appear in any one of eight locations immediately surrounding the Center token display location. Random Selecting this option causes the distractor to appear anywhere on the display space. This option can be used only when the Display Size has been set to Large. None Selecting this option disables the use of distractors. Synced If this box is checked then the distractor will be presented coincidentally with the onset of the token display. If it is not checked distractor presentation will be an asynchronous event governed by the Inter-Distractor Interval and the Range. Distraction can be any one of four types. Visual Selecting this option displays a randomly selected token from the Distractor Token(s) list. The token will be displayed in the color selected from the Token Color list or, alternatively a randomly selected color. Audio Selecting this option will present an auditory distraction and depending on the Audio Type selected, will be either a random tone drawn from the scale A below middle C to G# above middle C or a voice speaking a token randomly drawn from the Distractor Token(s) list. (Note: If dingbats are being used they normally have a character underling them. It is that character that will be used. So, for example, the WingDings smiley face is equivalent to J, the computer will speak the letter J.) Both The token will be present as both a visual (as described in Visual above) and an auditory (as described in Audio above) distractor. Either The computer will randomly decide whether the token will be displayed as a visual or an auditory distractor on each presentation. Either outcome has a.5 probability. 15

16 Distraction Duration specifies the duration of the distractor in milliseconds. Inter-Distractor Interval specifies the time in milliseconds between distractor presentations. Range specifies the variability of the Inter-Distractor Interval. Setting this value to something other than 0 will generate a constant probability distribution with a minimum value equal to the Inter-Distractor Interval minus the Range, a maximum value equal to the Inter-Distractor Interval plus the Range and a mean equal to the Inter-Distractor Interval. The Range may not be greater than the Inter-Distractor Interval. Distractor Token(s) is a list of tokens to be used as distractors. Payoffs CPTs are essentially Go/No Go signal detection tasks. It is well known that payoffs can affect response probabilities, biasing β. Most CPT analyze assume an ideal observer and a symmetrical payoff matrix, calculating β as simply the p(noise) / p(signal). When Payoff matrices are asymmetrical however the equation becomes: ߚ =ݐ ) ݐ ݎݐ ݎݎ ( ) ݏ ( + ( ) ݎ ݏ ) ݏ( (ℎ )ݐ + ( )ݏݏ Checking the Display Score box causes a display box to appear in the upper left corner of the test screen. The value displayed in this box can be set to an initial value. That value is subsequently modified by a specified amount, reflecting the participant s response (hit, miss, false alarm, correct rejection) at the end of each presentation cycle. Initial Value specifies the initial number or points allocated to the participant. Values for hits, misses, false alarms and correct rejections are entered into their respective boxes. The value for any outcome should be assigned a number. Numbers can be either positive or negative. If the initial value is set to 0 then the accumulated score from the last block will be used as the initial value for the current block Normative Data There is currently no normative data for any of our continuous performance tests. 16

17 References Mackworth, N. H. (1948). The breakdown of vigilance during prolonged visual search. Quarterly Journal of Experimental Psychology, vol. 1, pp.6-21 Rosvold HE, Mirsky AF, Sarason I, Bransome ED, Beck LH (1956) A continuous performance test of brain damage. J Consult Psychol 20:

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