Combining internet research and critical thinking, you will explore key milestones and potential concerns related to the aging brain. This assignment is designed to help you demonstrate your understanding of how this essential organ changes over time. Begin by selecting any two ages you are interested in learning more about, then:
Compare and contrast brain development and function at both ages. For example, you might look at the brain at two years old versus nine years old.
Summarize the cognitive abilities and/or possible age-related effects for each group.
Step 1: Research
Start by gathering information on brain function and development for the two ages you’ve chosen. Use credible sources such as those found in our Online Library (opens in a new window) or through scholarly internet searches. Do not use Wikipedia. You must include information from at least two different sources and avoid relying solely on one website.
Age 9: The Period of Refinement and Efficiency
By age 9, the period of rapid over-wiring is largely complete. The brain shifts its focus from creating connections to "pruning" and refining them, making the entire system much more efficient.
| Feature | Description |
| Brain Growth & Wiring | By age 9, the brain has reached about 90% to nearly 100% of adult size and is undergoing synaptic pruning. Connections that are frequently used become stronger and faster (often via myelination, which speeds up information transfer), while unused connections are eliminated. The brain is getting more specialized and efficient [Source 2]. |
| Neuroplasticity | While the brain remains plastic throughout life, its ability to reorganize and form new connections in general begins to decline from its peak. Learning is now more reliant on specific, focused effort rather than effortless, broad absorption. |
| Structural/Functional Focus | The frontal lobe (the control center) is much more developed than at age 2. Cognitive development is now shifting towards complex, integrated functions across different brain regions. |
Export to Sheets
Cognitive Abilities and Age-Related Effects
Age 2
This period is marked by an enormous cognitive leap centered on language acquisition and an emergent sense of self.
| Cognitive Abilities | Possible Age-Related Effects/Concerns |
| Language Acquisition | Rapid vocabulary growth; children can combine two or more words, and frequently use over-regularization (e.g., saying "foots" instead of "feet"). |
| Memory & Attention | Limited working memory and short attention spans. This limitation, however, is theorized to be an advantage (the "less-is-more" hypothesis), forcing the brain to focus on smaller, stronger patterns in linguistic input, thus aiding language learning [Source 1]. |
| Cognitive Control | Poor inhibitory control (impulsivity) and limited capacity to follow multi-step instructions (usually limited to two steps). Strong focus on actions of adults and imitation. |
| Vulnerability | The highly plastic and immature brain is especially vulnerable to chronic stress, neglect, or toxins. Negative experiences during this stage can build a fragile foundation for future learning and social-emotional capacity [Source 3]. |
Export to Sheets
Age 9
At this stage (middle childhood), cognitive abilities are more organized and abstract, moving toward the complexity of adult thought.
| Cognitive Abilities | Possible Age-Related Effects/Concerns |
| Working Memory & Executive Function | Significantly improved working memory, cognitive control, and selective attention (the ability to ignore distractions). Children can now engage in more proactive, goal-based thinking [Source 1]. |
Sample Answer
Brain Development and Function: Age 2 vs. Age 9
Age 2: The Period of Synaptic Explosion
At age 2, a child is in the middle of a phenomenal period of brain growth and wiring, often described as a "synaptic explosion" or "critical period."
| Feature | Description |
| Brain Growth & Wiring | By age 2, the brain is about 80% of its adult size and contains up to 50% more synapses (connections between neurons) than the adult brain, peaking around age 3. Over a million new neural connections are formed every second. The focus is on rapid proliferation of connections. |
| Neuroplasticity | This is the brain's period of highest plasticity (flexibility). The brain is incredibly susceptible to environmental influences—both positive and negative—which rapidly strengthen or weaken the connections that will form the brain's architecture for life. The brain is like a sponge, soaking up all stimuli. |
| Structural/Functional Focus | Development proceeds from the back of the brain (sensory areas like vision and hearing) to the front (frontal lobe). The frontal lobe, responsible for higher cognitive functions like executive control, is still highly immature. |