Visual search experiment.

Experiment template for visual search, based on psychopy.

In this specific case, a set of stimuli appear in a circle around the center of the screen. On each trial, there is a 50% chance of the target stimuli to appear. The task for the subjects is to respond as fast as possible whether the target is present in the current trial.

To recreate this experiment, you can download this repository, open it on psychopy and run the visualsearch.py script. When you run the script, you will be prompted with a dialog to enter the id of the participant.

After each trial, the result will be written to a file data.csv next to the script.

You can press the esc key to exit the experiment.

Changes to the experiment.

There is a few options that you can play with in this script:

• Change the stimuli images: By default, a set of stimuli are included in the stimuli folder, and can be targets (in the target folder) or distractors (in distractor). Feel free to change the images in this folder for your experiment, but note that only jpg and png files can be used.

• Change condition blocks: In the provided example, 3 blocks of trials with different settings. You can change the existing blocks or add more to your experiment by editing the experiment_setup variable in the visualsearch.py script. The avaliable settings are:

  • set_size: Number of elements appearing on each trial.
  • radio: All elements appear in a circle of radio radio around the fixation (you should keep it between 5 and 15).
  • repetitions: Number of trials per block.
  • feedback_timeout: How long the feedback should be shown (in seconds).
  • prerun_timeout: How long will it pass between the start of the trial and when the stimuli are shown (in seconds).
  • response_timeout: Maximum allowed response time (if the participant does not respond on time, the trial answer will be marked as incorrect).
  • rotate_images: If True, the stimuli will be rotated randomly on each trial.

• Change the introduction and goodbye texts via the introduction_text and final_text variables.

• Change the size of the stimuli with the size_of_stimuli variable.

CSV file fields.

Description of the fields in the csv file where the data is stored.

Key	Value
sId	Id of the subject for the experiment.
age	Subject age.
handedness	Subject handedness.
sex	Subject sex.
run_number	For each subject, the id of the run. This allows differentiating when the same the subject runs the experiment multiple times.
target_present	True if the target was visible in the trial, otherwise False.
set_size	Number of conditions in the trial.
radio	Distance from the center of the screen to each stimuli.
feedback_timeout	Period of time where only the fixation was shown (before stimuli appear) in seconds.
prerun_timeout	Period of time where the feedback was visible (after participant responds) in seconds.
timestamp	Timestamp marking the beggining of a trial (Unix timestamp).
response_time	Time between the moment when the stimuli are shown and the participant response is detected.
correct_answer	whether the participant answered correctly (True) or not (False).
pressed_key	What key was pressed by the participant.
response_timed_out	True if the participand did not respond on time.
stimuli_rotated	True if the stimuli were rotated randomly for this trial.