I'm planning an event-related fMRI-experiment to investigate the difference in processing natural and computer-generated facial emotion expressions. My supervisor and I are discussing different task instructions for the scanning session (see below).
Two often applied task instructions involve:
- Passive processing of facial emotion expressions Subjects are instructed to passively attend to the stimuli shown, no motor response or judgement required
- incidental processing of facial emotion expressions For instance, subjects are required to press a button in case an inverted face appears (in 10% of all cases for example)
As we do not have a MRI-compatible response box available, I prefer the passive processing task instruction, even though possible attention interferences may emerge as we cannot "control" cognitive processes of the subjects while scanning. My supervisor prefers the incidental processing because of these possible attention interferences and suggests subjects may answer with a hand signal. For me it will be impossible to track those hand signals because of the room setup and I am bothered about reviewers criticizing that we implemented a task that we were unable to control and report. Furthermore, I'm worried that the hand movements may interfere with the image quality as subjects are moving. My supervisor rejects all those arguments as sustaining attention of the subjects is the strongest argument for him and he thinks reviewers will criticize that if we implement a passive task.
How to implement an incidental task with low cognitive demands without a response box?
We discarded a recognition task after the scan (e.g. have you seen this picture before?) or a counting task during the scanning session (e.g. how many female faces?), as the cognitive load may be too high during the scanning session.