Knowledge Base

Important Concepts in Project Analysis

Independent Variables

Independent Variables

Independent Variables are factors that remain constant throughout an analysis, but can vary per participant. By default, each project contains the independent variables Age and Gender of the participant. These can be estimated by FaceReader, from the analyzed images. Alternatively, you can enter the values of these variables manually.

You can define more independent variables. Examples of independent variables are the native language of the test participant, or whether the participant has previous experience with the product under investigation.

Independent variables can be used to compare participant groups.

See Independent Variables

Stimuli and Event Markers

You can mark episodes that you are especially interested in. This can be, for example, a time fragment during which the test participant watches a certain commercial. Or it can be the time a participant is allowed to drink or eat a certain product you are interested in.

Stimuli

Use Stimuli to mark the parts of the analyses you are especially interested in. Stimuli are, for instance, the new commercials the test participants will watch or the pages of your newly developed website they will view. These time fragments have a fixed duration.

You can use a video fragment as Stimulus source, for example a video with the commercial. You can score a Stimulus manually during or after carrying out the analysis. But if you use The Stimulus Presentation Tool, any Stimulus included in the test is automatically recorded by FaceReader, so you do not need to score it manually.

See Stimuli and the Stimulus Presentation Tool

You can analyze the facial expressions over the time the Stimulus occurred and visualize the test participants face together with the Stimulus video. If you have the Action Unit Module you can also analyze Action Units and Custom Expressions. If you have the Vital Signs Module you can analyze heart rate, heart rate variability, and breathing rate.

Event Markers

With Event markers you can mark time fragments in the analysis, just like with Stimuli. In contrast to Stimuli, Event markers have no fixed duration and are not linked to a video. With Event markers you can, for example, mark episodes where something unexpected occurs, like a visitor entering the room, or mark events that have no fixed duration, like drinking a fruit juice. You score an Event marker manually and score it again, or score another one to set the stop time of the marker.

See Event Markers

Stimuli and Event Markers in The Observer XT

Stimuli and Event markers can be exported into the detailed log. If you use FaceReader together with the annotation software The Observer XT, the Stimuli and events are imported into The Observer XT as state events. These can then be used to select the time fragments for further analysis.

See FaceReader with The Observer XT

The Stimulus Presentation Tool

With the Stimulus Presentation Tool you can automatically present Stimuli to test participants. You do not have to score Stimuli manually. You can organize the Stimuli in Tests (see below). The Stimuli and analysis are automatically synchronized.

See The Stimulus Presentation Tool

Tests

In a test you define which Stimuli to present to test participants and in which order. Tests are carried out with the Stimulus Presentation Tool. When you carry out a test, a participant and analysis is automatically added to the project. The Stimulus Presentation Tool displays the Stimuli during the test while FaceReader records and/or analyzes the participant's face.

See Define a Test

Calibration Versus Baseline Correction

Instead of participant calibration, or continuous calibration, you can define a Neutral stimulus. Score this Stimulus when the test participant watches a neutral set of images or a neutral video fragment. In the analysis, calculate the facial expressions during the experimental Stimulus relative to the facial expressions during the neutral Stimulus.

Source: FaceReader 10 Reference Manual (Help), Noldus Information Technology