* INCLUSION CRITERIA:
Inclusion Criteria for In-lab Participants
A subject can be included in the in-lab portion of the study if he/she:
* is in good general health;
* is between 18 and 65 years old;
* has visual acuity of 20/40 in at least one eye (corrected with contact lenses is okay);
* has no hearing impairment requiring a hearing aid.
* is capable of understanding the procedures and requirements of this study;
* is willing and able to provide his/her own informed consent.
Inclusion Criteria for On-line Participants
A subject can be included in the on-line portion of the study if he/she:
* is in good general health;
* is between 18 and 65 years old;
* is capable of understanding the procedures and requirements of this study;
* is willing and able to provide his/her own informed consent.
Inclusion Criteria for Genetic Screening/Off-site Participants
A subject can be included in the off-site portion of the study if he/she:
* is between 13 and 65 years old;
* is in general good health;
* is capable of understanding the procedures and requirements of this study;
* is willing and able to provide his/her own informed consent.
EXCLUSION CRITERIA:
Exclusion Criteria for In-lab Participants
A participant is not eligible for participation in the in-lab portion of this study if any of the following exclusion criteria are present, as self-reported by the prospective participant or determined during clinical testing following consent:
* Participant is pregnant
* Participant has serious vision or hearing problems; for some sub-studies focused on mechanisms of normal color vision, subjects who are colorblind will also be excluded;
* Participants without consent capacity will not be enrolled;
* Participant has a debilitating neurological disorder (examples include, but are not limited to: brain tumor, epilepsy, Alzheimer's Disease, Parkinson's Disease, multiple sclerosis) or a psychiatric disorder (examples include, but are not limited to: schizophrenia, clinical anxiety, severe depression, attention deficit hyperactivity disorder (ADHD), schizophrenia). Patients with non-debilitating conditions such as prosopagnosia, prosopometamorphosia (PMO), or aphantasia will have their conditions noted but will not be excluded);
* Participant has had a serious head injury or has a history of brain surgery. Head injury is defined as an injury to the brain from some external force resulting in loss of consciousness of 30 minutes or more;
* Participant has psychoactive drug or alcohol abuse or dependence in the past three months, as determined by the Drug Abuse Screening Test (DAST), except nicotine and caffeine. A score of 6 or greater on the DAST will be considered exclusionary. The effects of nicotine and caffeine in neuroimaging are attenuated if participants do not smoke or consume caffeine 2-3 hours before the scan session; Over-the-counter medication/herbals will not be a criterion for exclusion;
* Participant is an NEI employee within the Perception, Cognition and Action section.
Additional Exclusion Criteria for MRI Sub-studies
Contraindication to MR scanning include the following: metallic tattoos or metallic eyeliner; claustrophobia; inability to lie still on their back for approximately 2 hours; implanted cardiac pacemaker or auto-defibrillator; surgical aneurysm clips; implanted neural stimulator; artificial heart valves or pumps; metal fragments in cranial cavity, body or eyes (e.g., history as a metal worker); nitroglycerin patch (foil backer); cochlear implants (tubes are okay); weight \> 450 lbs; metal rods, plates, screws in body; shrapnel or bullet wound; intrauterine device (IUD) not approved on mrisafety.com (most IUDs are okay); vestibular or inner ear abnormality such as Meniere's disease; metallic braces; hair extensions attached with metallic wires; transdermal patches; movement disorders; dental implants; consumed of nicotine or caffeine in the two hours prior to the experimental session. Subjects may participate in this study but will not be allowed to have a 7.0 T MRI scan if they have metallic dental crowns or a bridge.
Exclusion Criteria for Genetic Screening/Off-site Participants
Off-site participation will be biased to participants with XY chromosomes until the genetic sequencing capability changes. We do not limit to just XY patients to provide the possibility of evaluating newer genetic sequencing capacity and because sequencing on XX can provide some information, even if it is not as decisive as on XY patients.
Exclusion Criteria for On-line Participants
Subjects may not participate in the on-line portion of the study if they:
* Do not have access to compatible equipment. For example, smartphone screens are too small to be used. The online platform will outline which devices may be used.
* Are unwilling to allow permission for JavaScript to run on the site and disable any script blockers.
* Are unwilling to agree to the on-line testing platform's terms and conditions.
