8a: Visual Memory

Definition: Iconic memory refers to the fleeting visual memory that holds an image of a visual stimulus just after it is perceived. This type of memory allows the retention of visual information for a very short period of time.
- briefly stores visual info after a stimulus disappears
- analogy: a mental snapshot that fades within ms
Stimulus Duration: Iconic memory can last from 15 milliseconds (ms) to 500 ms.
- Whole Report Method: In experiments utilizing this method, individuals were asked to report as many letters as possible presented briefly (for example, the letters G, F, C, J, A, P, W, C, S, T, N, O).
- Regardless of the stimulus duration, findings indicated that participants could reliably report approximately 4 items.
- suggests limited capacity of visual memory
Partial Report Method: In alternative experiments, such as those conducted by Sperling (1960), participants were cued to a specific row of letters after presentation, allowing for a more focused retrieval.
- Results showed that individuals could accurately report the letters from the cued line, demonstrating a “partial report advantage,” where participants performed better than in the whole report scenario.
- iconic memory holds more info than whole report reveals, it just fades too quickly to access all of it without a cue.

High Capacity: Iconic memory can hold a significant amount of visual information.
Rapid Decay Function:
- Tested by varying the time between the display of visual information and the presentation of the tone cue.
- Accuracy significantly decreases with a delay of just 100ms, indicating that by 1000ms no relevant information is retrievable (which shows no significant difference compared to the whole report).

0 ms delay (tone right after display): Participants recalled almost all letters from the cued row. Iconic memory was fresh.

• 100 ms delay: Accuracy dropped. The visual trace had already started fading.

• 1000 ms delay (1 second): Performance was no better than in the whole report method. The iconic memory had completely decayed.

Susceptibility to Overwriting: Iconic memory can be overwritten or masked by new stimuli, especially if they occur shortly after the original stimulus presentation.

Definition: VSTM refers to the capacity to hold visual information in an accessible state for a longer duration (compared to iconic memory) but with limited capacity.
Comparison with Iconic Memory:
- Capacity: VSTM has relatively low capacity compared to iconic memory.
- Duration: VSTM has an indefinite duration if information is actively maintained, contrasting with the short-lived nature of iconic memory.

Methodology by Luck & Vogel (1997):
- Participants engaged in a task to determine if two arrays displayed to them were the same or different, often referred to as the “same/different” task.
- This task measured the correctness of responses as a function of load (the number of items in the set).
- Set Sizes Tested: 4, 8, and 12 items were tested in the experimental design.
- Results Representation:
  - Graph: Percentage of Correct Responses (% Correct) plotted against Set Size.
  - Findings demonstrated varying levels of accuracy based on the load.

All stimuli are robustly represented in VSTM, revealing that they are not sensitive to variations in timing between the presentation of two arrays (within reasonable limits).
Unlike iconic memory, not all items displayed in a visual array are guaranteed to enter the VSTM, suggesting selectivity in what is retained.
VSTM is resilient against masking, meaning it can hold its contents despite the presence of interfering stimuli in the environment.

once something enters VSTM, it’s stored with stable detail
if you're shown two sets of images or objects, one after the other, and there's a short delay between them, your memory of the first set doesn’t get weaker just because of that delay.
not all items enter VSTM (selective)
if new stimulus appears, VSTM can still hold onto the original content

Question: What are the similarities between iconic memory and visual short-term memory on one hand and the two stages of the two-stage attentional bottleneck model on the other hand?
- Considerations: Analyze how both memory types operate regarding information processing, retention duration, and capacity in relation to attention mechanisms as described in theoretical models.