- Language Delay
- Language Development
- Language Disorder
- Law of Effect
- Lawrence Kohlberg
- Leadership
- Learned Helplessness
- Learning Curve
- Learning Disability
- Learning Theory
- Learning-To-Learn
- Left-Brain Hemisphere
- Leon Festinger
- Lewis Terman
- Libido
- Lie Detection
- Localization (Brain Function)
- Localization (Sensory)
- Locus of Control
- Logical Thinking
- Longitudinal Study
- Loss and Grief
