An often-overlooked contributor to underachievement is undiagnosed learning differences. A gifted individual is less likely to be diagnosed with a learning disorder than a non-gifted classmate, as the gifted child can more readily compensate for their paucities. This masking effect is dealt with by understanding that a difference of one standard deviation between scores constitutes a learning disability even if all of the scores are above average. Assessments may also fail to identify some gifted students entirely because their underachieving behaviours keep them from being recognized as exceptional.