Inclusion Criteria:  diagnosis of SCD ages 8-16 years maintained on monthly blood transfusions consistently for at least 3 months. patients will be proceed to the intervention phase only if they have a T-score > 75th percentile for Omission Errors on the Conners' Continuous Performance Test, 3rd Edition (CPT-3) or a T-score > 75th percentile for the Inattention subscale of the ADHD Rating Scale, Fifth Edition (ADHD-RS-V).  Exclusion Criteria:  estimated Intelligence Quotient < 70 motor, visual, or auditory impairment that prevents computer use known diagnosis of a mental health condition that precludes, or takes treatment precedence over, participation in cognitive training history of photosensitive seizures insufficient English fluency.