By: RJ Allen, AD Baddeley, GJ Hitch
Presentation By: Danielle Paterno
- Found a relatively automatic but fragile visual feature binding mechanism in working memory
- Into: What is working memory and the episodic buffer?
- Baddeley and Hitch Model of Working Memory – limited capacity system for the temporary storage and manipulation of information obtained through sensory systems
- The subsystems of working memory: Acquiring information from different sensory organs that enters and is manipulated in separate areas of the brain
- Visuospatial sketchpad – stores and processes information in a spatial form
- Phonological loop – deals with spoken and written material that enters the store and is repeated mentally (like in a loop) to retain the information
- Central Executive – a higher system of cognitive function that requires attention responsible for information integration and interpretation
- Baddeley and Hitch propose adding a new subsystem (episodic buffer) to explain the binding of features and chunking components of multi-featured information so the retrieval of one component evokes the remainder
- Working hypothesis: access from subsystems to episodic buffer goes through the central executive therefore requiring attentional resources
- Purpose:
- investigate the process of binding the features of frequently perceived visual stimuli
- attempt to provide evidence for a theoretical bridge between what is known about visual short term memory and a broader working memory system
- working memory is capable of temporarily holding multifeature objects in an integrated form; however, whether simple combinations of visual features are bound through effortful, active processing, or if this can be achieved in a relatively automatic manner, at no extra cost to executive resources is not clear
Experiment 1
Four conditions objects were presented
- Shape-only: four empty shapes were presented (250ms) à blank screen (900ms) à test probe (In original array? Yes/No)
- Color-only: four blocks of color were presented (250ms) à blank screen (900ms) à test probe (In original array? Yes/No)
- Either shape or color: Told either memory for the shape or color of an object in the original array would need to be recalled but did not know which until test – four colored shapes were presented (250ms) à blank screen (900ms) à test probe = either unfilled shape or colored block (In original array? Yes/No)
- Combination: four colored shapes were presented (250ms) à blank screen (900ms) à single colored shape presented at test (In original array? Yes/No)
Results
– Color only results were better than shape only
– The either condition and the combination conditions did not significantly differ
– Memory for shapes was significantly better when tested in the single feature condition than in the either condition
– Memory for color was not significantly different when tested in the single feature condition than in the either condition
Shape is more complex than color leading to a greater susceptibility to partial information loss
Experiment 2
Is the binding demonstrated in Experiment 1 created and maintained in working memory automatically, or are executive based attentional resources required?
Due to previous evidence of the frontal lobe involvement in feature binding, indications are strong for attentional resources from the central executive playing an important role in feature binding.
Examines the effects of attention-demanding concurrent tasks on binding under the short exposure conditions of Experiment 1.
Participants performed Experiment 1 whilst performing a backward counting task to sufficiently load the central executive and disrupt attention.
Results
In line with experiment 1, memory for combinations of shape and color was equivalent to memory for the shapes themselves and accuracy was highest in the test of color alone.
Binding of features appears to require the same resources/demands to process and maintain as less salient feature dimensions.
Backwards counting did show a substantial detrimental effect in every condition
Experiment 3
Attempt a different concurrent task to load the central executive
Participants performed recall of digit strings concurrently with the memory task
- did sufficiently disrupt visual memory performance equivalently across shape, color, and combination conditions
Experiment 4
New concurrent task: backward counting in steps of three, performed only during encoding and retention
Continued to support evidence that shape and color can be bound into integrated 
object representation and held in working memory without additional support from the central executive
Experiment 5
Compared simultaneous representations of the stimuli to sequential to test fragility of integrated object representations
If representations of feature combinations in working memory are more fragile than those for single features, accuracy in the binding condition should be low with sequential presentation relative to simultaneous presentation; likewise single features should be less susceptible to retroactive interference
Sequentially:
Memory for combinations of features was significantly worse to a greater degree than shape or color memory alone.
Concludes: features may be integrated with relatively no additional CE demands the connections between them are more fragile