 Genetic variation is a primary contributor to individual differences in baseline dopamine neurotransmission. Individuals with specific alleles in genes coding for high baseline dopamine demonstrate better performance on tasks probing working memory, cognitive control, and social cognition. Genetic variants in baseline dopamine neurotransmission would therefore be expected to modulate performance-enhancing effects of L-DOPA, such that individuals with low endogenous would be expected to have increased performance upon exogenously increasing dopamine neurotransmission; whereas individuals with high endogenous dopamine would be expected to have performance deteriorate from exogenously increasing dopamine neurotransmission. In support of this hypothesis, a recent study found an interaction between L-DOPA administration and endogenous dopamine neurotransmission as indicated by a polygenic score pooled across catechol-O-methyltransferase COMT, dopamine transporter protein DAT, dopamine D1 receptor DRD1-3 on motor learning performance, such that individuals with a combination of alleles coding for higher baseline dopamine demonstrated a weaker learning benefit from L-DOPA, whereas individuals with a combination of alleles coding for lower baseline dopamine demonstrated a stronger learning benefit from L-DOPA. These data demonstrate the non-linear relationship between performance and dopamine levels, suggesting that any investigation of potential effects of boosting dopamine neurotransmission as a means of boosting learning needs to account for baseline dopamine neurotransmission. 