What are attributes?

Attributes are features that can be manipulated in building an experiment in PsyScope. Attributes of experiments, trials, and events can be changed. Because each of these structures possess different features, they each have different sets of attributes associated with them. A thumbnail sketch of attributes for the different types of structures is provided below to give the you a feel for features that can be easily manipulated in PsyScope.

Experiment Attributes : Attributes for experiments deal with broad operational features of an experiment. For instance...

Input devices : Allows you to specify how responses will be indicated during the experiment, e.g., by mouse, keypress, and/or buttonbox.

Timer : Allows you to specify which timer to use when measuring response latencies (internal Mac timer or buttonbox timer).

Number of trials per rest : Allows you to specify how many trials should be presented before allowing participants to take a break.

Trial Template Attributes : The trial attribute we will deal with most frequently is Condition Name. This attribute provides a descriptive label that aids in data analysis by sorting individual trials into their appropriate condition.

Event Attributes : There are two types of attributes falling under the Event attribute category : Stimulus Attributes and Event Attributes. The menu of stimulus attributes varies depending on the type of event presented. For instance, presentation of a text event will allow you to change the font, color, and position of the event, while attributes for a sound event will allow you to specify features such as the volume. Event attributes are those features associated with any event, for instance, its duration.

To see a full listing of attributes for a specific structure (Experiment, block, trial, etc.) you should open its attribute window. The Attributes window for specific structures are typically accessed through a button labelled ŒAttributes¹ within the structure¹s window. For instance, if you wanted to see the Experiment attributes window, you should first make sure you are looking at the Design window. Next...

1) Double click on the Experiment icon (red psi symbol) to open the Experiment window.

2) Inside the Experiment window is a button labelled ŒAttributes.¹ Click the mouse in this box. This will open the attributes window where you will see a menu list of attributes that can be varied. Adjacent to the list of attributes is a box with the word Default and a downward pointing arrow inside of it.

The Attributes window for other structures (trial templates, blocks, etc.) can be located in a similar fashion. Simply open the window for the relevant structure and click on the Attributes button.

**There is one exception to this. Accessing the attributes for Events requires you to simply double click on the event itself. This takes you directly to the Stimulus Attributes window.

Initially the attributes for all structures in the experiment are set to Default values. If you wish to change any values you may do so within the attributes window of the appropriate structure. You can change the settings for any attribute by clicking the mouse cursor in the box alongside the desired attribute. Holding the mouse button down will open up a pop- up window with the following options

Set to:

Default:

Vary by:

Script:

Set to: Selecting this option allows you to assign a fixed value to this attribute. Choosing this setting will open a dialog box specific to this attribute. Whenever this event or object is presented or activated the selected setting will be used. For instance, if you were presenting a text event and you wished to change font size you could have the font size ³set to² a particular size instead of the 12 point default value.

Default: This value is automatically assigned within PsyScope. Selecting this option returns the value to the pre-established settings.

>Vary by: This option allows the attribute to vary from trial to trial. The specific values to take on are determined by a list of values that is somehow linked to the experiment. When the ŒVary by¹ setting is selected, a second pop-up menu appears to let you specify where the values will be found. We typically rely on internal or external list objects for this purpose, so we would select ŒList¹ in the second pop-up menu.

Selecting the ŒList¹ option causes another window to open. This window has you identify the appropriate list and field (column) within the list to assign values for this attribute. (See List Objects in PsyScope below.)

Script: We typically do not rely on this setting. It allows you to link the value of an attribute to entities defined within the script of the experiment.

Lists provide a means for varying parts of a template from trial to trial. There are two types of list files in PsyScope: Internal and External. The fundamental difference between the two is that the values in internal lists are part of the Psyscope script and therefore Œtravel¹ with the experiment file. The values in internal files are viewable only within the PsyScope environment. External lists begin as separate text files and are linked to the experiment within PsyScope. Thus, these list files can be created and viewed with any text editor. One need not have a copy of PsyScope to view the contents of external files, consequently, they can be edited without opening PsyScope. Using external files is advantageous when the list of possible values is long. Despite these differences the two types of list objects function in very much the same way.

Structure of Lists. A list consists of a list of items in corresponding Œfields¹ (represented by columns across a row). A field simply refers to the type of attribute to be found in that particular column, for instance, the values listed may provide colors, fonts, or font sizes for text events. Once a field is defined, the entries within that column must be consistent with the definition. For instance, if the field is defined as ŒColor¹ the entries Œred,¹ Œgreen,¹ and Œblue¹ are acceptable entries in the list, but ŒHelvetica,¹ ŒTimes,¹ and ŒPalatino¹ are not.

Several different fields can be defined within the same list. In fact, this is the advantage of the list structure. The color, font, and position of an event can be varied simultaneously. Each time a trial is run, an item (row) is selected from each list. All values associated with that item apply to the current trial. Thus, each item in a list defines a unique trial in the experiment.

Written by: Penny Yee, Hamilton College

Modified by: Tiffany Mattson, Hamilton College

Last Modified: 6/4/96