Summary: New research indicates the existence of an unconscious iconic memory store that supports predictions made by the global workspace theory of consciousness. It also shows that visual masking does not erase memory traces of masked stimuli but only limits conscious access.
Source: Damian Pang / University of Pennsylvania
Visual masking renders briefly presented images invisible. New research published in Scientific Reports shows that repeating strongly masked stimuli can elicit conscious perception.
Visual masking was long held to erase or overwrite memory traces of an image that is briefly presented. This new study indicates that memory traces are likely retained for brief periods of time but with limited conscious access. Visual data can accumulate in the absence of conscious awareness in this memory buffer store and elicit clear perception when sufficient evidence is available.
The global workspace theory of consciousness suggests that perception is the result of bottom-up and top-down processes: Top-down directed attention and bottom-up stimulus strength both play an important part in what ultimately enters awareness.
This process requires information to be stored subliminally and has led to predictions for the existence of such a subliminal memory buffer store that lasts at least a few hundreds of milliseconds. This new research offers empirical evidence in support of such a buffer store.
This research by Damian Pang and Stamatis Elntib found that this newly described memory buffer is time-sensitive. Meaningful extraction becomes severely compromised after around 300 milliseconds and is almost completely lost after 700 milliseconds. This time course is strikingly similar to the duration of iconic memory.
While this memory buffer conforms to iconic memory in many ways, the stark difference is that its content can be unconscious. For this reason, this memory store does not seem to fit into any existing memory classification but conforms to the theoretical predictions made by the global workspace theory.
This study also shows that perception of a visual stimulus can be controlled to a very high degree when masked and repeated by varying the repetition interval. Future research in the areas of perception, consciousness, memory, and attention could employ this method to control awareness.
About this memory research news
NeuroscienceNews would like to thank Damian Pang for submitting this research news for inclusion on the website.
Strongly masked content retained in memory made accessible through repetition
A growing body of evidence indicates that information can be stored even in the absence of conscious awareness. Despite these findings, unconscious memory is still poorly understood with limited evidence for unconscious iconic memory storage.
Here we show that strongly masked visual data can be stored and accumulate to elicit clear perception.
We used a repetition method across a wide range of conditions (Experiment 1) and a more focused follow-up experiment with enhanced masking conditions (Experiment 2). Information was stored despite being masked, demonstrating that masking did not erase or overwrite memory traces but limited perception.
We examined the temporal properties and found that stored information followed a gradual but rapid decay. Extraction of meaningful information was severely impaired after 300 ms, and most data was lost after 700 ms.
Our findings are congruent with theories of consciousness that are based on an integration of subliminal information and support theoretical predictions based on the global workspace theory of consciousness, especially the existence of an implicit iconic memory buffer store.