Effects of Multiple-Session Transcranial Direct Current Stimulation (tDCS) on Behavioral, Physiological, and Electrophysiological Measures With Adults With Autism Spectrum Disorder (ASD)

The purpose of this clinical trial is to investigate the effects of multiple sessions of transcranial direct current stimulation (tDCS) delivered while participants complete tasks that target social learning with high functioning adults with ASD and/or high traits of ASD. The main question it aims to answer is: What are the effects of multiple sessions of active compared to sham tDCS, with tDCS simultaneously paired with social learning tasks, from employing a within-subject, cross-over randomized controlled trial design? Participants will: * Complete a randomly assigned block of 5 sessions of active and a block of 5 sessions of sham tDCS, with a four-week break occurring between the two blocks. * Complete social learning tasks simultaneously during receipt of tDCS at each session (whether receiving active or sham tDCS). * Complete behavioral, physiological, and electrophysiological testing before and after each block of active or sham tDCS. * Complete a social validity questionnaire after completion of the study.

Inclusion Criteria: 1. Age 18-35 years 2. Proficient in English 3. Classification of autism or autism spectrum disorder on Autism Diagnostic Observation Scale, 2nd Edition (ADOS-2) or score of \>= 17 on Autism Quotient (AQ) 4. Good or corrected vision and hearing 5. Right-handed based on the Edinburgh Handedness Inventory 6. Score of \>= 85 on Shipley-2 Exclusion Criteria 1. No known loss of consciousness for \> 5 minutes 2. No immediate biological family members with a history of epilepsy or seizure disorder 3. No major medical needs (e.g., neurological disorders such as a seizure disorder; long-term illness) 4. No surgically implanted metal above the neck (example: metal pins or plates, cochlear implants, aneurysm clips, brain electrodes) 5. No hospitalization for depression, anxiety, or substance abuse in the past 12 months 6. No individuals who are currently pregnant 7. No pacemakers 8. No history of neurological disorders such as stroke, multiple sclerosis, bipolar disorder, encephalitis, epilepsy, seizure disorder, or amyotrophic lateral sclerosis