Characteristics of Memory Stores: Duration
This page explores the duration of information retention in short-term memory (STM) and long-term memory (LTM), highlighting two influential studies that have shaped our understanding of memory persistence.
Duration of Short-Term Memory
Peterson and Peterson (1959) conducted a groundbreaking study to determine the duration of short-term memory. Their experiment utilized nonsense trigrams and a distraction task to prevent rehearsal.
Procedure:
- Participants were shown a nonsense trigram (e.g., WKQ) along with a three-digit number.
- They were instructed to count backward by threes from the given number while viewing the trigram.
- The delay between seeing the trigram and recalling it increased by 3 seconds after each trial.
Definition: A nonsense trigram is a sequence of three letters that doesn't form a meaningful word, used to minimize the influence of prior knowledge on memory performance.
The researchers calculated STM duration by identifying the longest delay at which participants could correctly recall the nonsense trigram.
Highlight: The study concluded that short-term memory has a duration of 18 to 30 seconds without active rehearsal.
This finding has significant implications for understanding the temporary nature of information in STM and the importance of rehearsal for retaining information beyond this brief window.
Duration of Long-Term Memory
Bahrick (1975) investigated the duration of long-term memory through a fascinating study on face recognition over extended periods.
Procedure:
- American university graduates were asked to match names to photographs from their high school yearbooks.
- The study included participants who had graduated at various time points in the past.
Results:
- 90% of participants correctly matched names and faces 14 years after graduating.
- 60% of participants accurately matched names and faces 47 years after graduation.
Highlight: Bahrick's research suggests that long-term memory can potentially last an individual's lifetime.
This study demonstrates the remarkable persistence of certain types of information in LTM, particularly for personally significant memories like those associated with high school classmates.
Comparison of Memory Stores
The page concludes with a table summarizing the characteristics of all memory stores:
| Characteristic | Sensory Register | STM | LTM |
|----------------|-------------------|-----|-----|
| Capacity | Very large | 5 to 9 items (7±2) | Unlimited |
| Encoding | All 5 senses | Acoustic | Semantic |
| Duration | Very limited | 18 to 30 seconds | Lifetime |
This comparison highlights the distinct properties of each memory store, from the fleeting but rich sensory register to the limited but crucial STM, and finally to the vast and enduring LTM.
