| Key Term | Definition |
| Nature | |
| Nurture | |
| Continuous Development | |
| Discontinuous Development | |
| Stage Theories | |
| Cognitive Development | |
| Neurotransmitters | |
| Reliability | |
| Interrater Reliability | |
| Test-Retest Reliability | |
| | Key Term | Definition |
| Validity | |
| Internal Validity | |
| External Validity | |
| Structured Interview | |
| Clinical Interview | |
| Correlation Coefficient | |
| Direction-of-Causation Problem | |
| Microgenetic Design | |
| Counting-On Strategy | |
|