Types of Memory: Sensory, Short-Term, Long-Term, Iconic, Echoic
📘 7.1 Types of Memory: Sensory, Short-Term, Long-Term, Iconic, Echoic
Memory is the process of encoding, storing, and retrieving information. Different types of memory operate at various stages, serving specific cognitive functions.
🧠 1. Sensory Memory
Definition:
Sensory memory holds incoming sensory information for a very brief period (milliseconds to a few seconds), allowing initial processing before further encoding.
Key Features:
- Duration: < 1–3 seconds
- Capacity: Large but unprocessed
- Modality-specific (iconic, echoic, haptic)
Purpose:
Acts as a buffer, giving the brain time to select relevant information for further processing.
📸 a) Iconic Memory (Visual)
- Holds visual images for about 0.5 to 1 second.
- Named by Ulric Neisser, based on the Greek word “eikon” (image).
Example:
- When a flash of lightning appears, we briefly retain the visual impression.
🔊 b) Echoic Memory (Auditory)
- Holds auditory input for about 3–4 seconds.
- Helps in speech recognition and auditory tracking.
Example:
- When someone says something and you ask “What?”—but then recall it a second later, that’s echoic memory at work.
🔄 2. Short-Term Memory (STM)
Definition:
STM temporarily stores and processes a limited amount of information for about 15 to 30 seconds unless rehearsed.
Key Features:
- Capacity: 7 ± 2 items (Miller’s Law)
- Duration: 15–30 seconds
- Encoding: Acoustic or verbal
Example:
- Remembering a phone number long enough to dial it.
Real-life use:
- Holding an OTP received on mobile for typing into a form.
📦 3. Long-Term Memory (LTM)
Definition:
Stores information permanently for later retrieval; virtually unlimited capacity.
Key Types:
- Explicit (Declarative): Facts & events (e.g., names, historical dates)
- Episodic (personal experiences)
- Semantic (general knowledge)
- Implicit (Non-declarative): Skills, habits (e.g., riding a bicycle)
Example:
- Remembering concepts learned in high school.
- Procedural memory for typing without looking at the keyboard.
🔍 Comparison Table
| Type of Memory | Duration | Capacity | Encoding | Example |
|---|---|---|---|---|
| Sensory | <1 to 3 seconds | Large | Sense-based | Seeing a light flash, hearing a tone |
| Iconic | ~0.5 seconds | Visual sensory | Visual | Flashing images |
| Echoic | ~3–4 seconds | Auditory | Auditory | Echoes of spoken words |
| Short-Term | 15–30 seconds | 5–9 items | Mostly acoustic | Recalling a number |
| Long-Term | Years/lifetime | Unlimited | Semantic/Visual | Remembering how to ride a bike |
🏛️ Application in Governance & Education
- E-learning:
- STM and LTM distinctions help in designing chunked content for better retention (e.g., Mission Karmayogi training modules).
- Exam Preparation:
- Effective UPSC strategies often involve transferring STM (cram memory) to LTM (conceptual understanding) through revision and retrieval practice.
- Policy Communication:
- Public campaigns should repeat messages across multiple sensory channels (visual + audio) to optimize sensory and short-term memory for action triggers (e.g., COVID safety jingles).
🧠 Real-World Examples
| Situation | Type of Memory Used |
|---|---|
| Remembering an OTP briefly | Short-Term Memory |
| Recognising a road sign instantly | Iconic (Sensory) Memory |
| Understanding spoken instructions | Echoic Memory |
| Recalling your UPSC roll number | Long-Term Semantic Memory |
| Recalling the sound of a jingle | Long-Term (Implicit) Memory |
✍️ Answer Writing Tips
- Start with a clear definition of memory and introduce the classification.
- Explain each memory type in a structured format (definition, duration, encoding, example).
- Use Indian governance or education-related examples to show relevance.
- End with a comparison table or flowchart if space allows.
