The counterbalance construct group provides a placeholder for one or more constructs on the trials timeline. This group can be allocated to one or more cells on the trials screen for random construct selection and/or random spatial allocation of constructs on each trial.
- a group containing one construct allocated to two screen cells will allocate that construct randomly to one of the two cells (random placement)
- a group containing two constructs allocated to one screen cell will allocate a random construct to that cell (random construct selection)
- a group containing two constructs allocated to two screen cells will allocate those constructs randomly to the two cells (random placement)
- a group containing three constructs allocated to two screen cells will allocate two random constructs randomly to the two cells (random construct selection, random placement)
- and so on...
Creating a counterbalance construct group
Counterbalance construct groups can be added to trials timelines. Click New item, select
Counterbalance construct group from the type list and select one of the following creation options:
New: create a new counterbalance construct group.
Copy: copy another counterbalance construct group from the current study.
Editing counterbalance construct group
Click anywhere along its row (Figure 1) to open the editor.
Figure 1. Open construct editor
Adding a construct to the group
Any number of constructs can be added to a counterbalance construct group. In edit mode, click on the
Construct dropdown menu and select
New item... (Figure 2)
Figure 2. Add new construct
When creating a new construct, you can choose to start with a blank slate, to copy an existing construct from this or another trial, or to clone an existing construct from another trial.
Cloning is an important part of response button position randomization and response keyboard key value randomization across multiple trial blocks.
Selecting a construct to edit
In edit mode, click on the
Construct dropdown menu and select the construct that you wish to edit (Figure 3). For details on editing specific constructs, please see their individual reference documentation.
Figure 3. Construct menu
Removing a construct from the group
In edit mode, click on the
Construct dropdown menu and click Delete next to the corresponding construct (Figure 3).
In edit mode, the following properties can be set via the timing table:
- Start mode
Fixed: start time will be measured from the beginning of the trials timeline.
Offset from previous item: start time will be measured from the end of the previous item on the trials timeline. If there is no previous item, or the timeout of the previous item is set to
nil(infinite), then start time will be measured from the beginning of the trial.
- Start time (ms): when to initiate construct.
- Duration mode
Fixed: duration will be a fixed time period.
Random: duration will be a random time period bound by minimum and maximum values.
Factor: duration will be a randomly chosen level from the factor selected.
Level: duration will be set to the value of the chosen level.
- Timeout (ms): duration of construct presence.