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=Cognitive Blink Suppression=

Cognitive blink suppression is a physiological phenomenon in which the act of blinking interferes with the ability to process cognition in the mind. Blinking is an essential human function, serving to protect the eyes, and thus humans blink countless times in a given day. However, humans blink 15-20 times a minute, far more than what is actually required for ocular lubrication. This suggests that cognitive processes, such as memory and focus, are interrupted quite frequently, more than what seems biologically necessary, throughout the course of a normal day. Specifically, the processes of iconic memory storage and recall, object perception , and attention are examples of processes negatively affected by voluntary blinking. Continued research on cognitive blink suppression looks to clarify which processes are affected by eyeblinks and to provide further evidence that definite causal relationships exist between blinking and various cognitive functions.

Early theories
Early theories on the relationship between blinking and cognition focused on determining a clear relationship between blinking and the brain. As blinking physically obscures the eyeball, initial research examined whether people consciously noticed a loss of vision as they blinked. Participants did not report a vision loss, despite reporting dimmed lights in a room as noticeably disruptive. This suggests that some neural mechanism is responsible for vision constancy during blinks. As well, voluntary blinking was found to be more disruptive than temporarily removing the stimulus from view. These early studies clearly established a connection between blinking and cognition, allowing for further research to continue with the assumption that blinking and thinking are related.

Types of blinks
There are three different types of blinks, of which voluntary blinks and endogenous blinks are most relevant to cognitive blink suppression research:

Continued research on the relationship between thought processes and eyeblinks focused on the causal effect of cognition on endogenous blink rates. Several early studies proposed and supported the theory that a high cognitive load slows involuntary, endogenous blinking. An inverse relationship between blinking rates and cognitive function has been shown in many studies since. For example, surgeons greatly reduce their rate of blinking while performing surgery (often by over 60%), because surgical procedures require a great deal of attention, careful thinking, and quick, accurate reflexes. This is despite the fact that accurate vision requires frequent blinking to replenish the tear film on the eye, which suggests that it is more critically important to maintain fixation at certain points in time. People often adjust their blink timings so that eyeblinks are performed more often when cognitive load is lowest, presumably because it is safe to do so without missing any important visual inputs. Therefore, blink rates can actually reflect the extent of cognitive processing that is occurring over a given time period in a person’s brain.

Saccadic eye movements
Research on saccades also contributed to early knowledge of the causal relationship between blinking and thinking. Saccades are the rapid movement of both eyes in the same direction and are thought to be neurologically similar to eyeblinks. Like eyeblinks, they also disrupt vision, because their jerky movements displace the image on the retina, and people cannot consciously detect that their vision is being interrupted. Saccades activate many of the same areas of the brain as eyeblinks, and have been shown in studies to negatively affect visual sensitivity in a phenomenon known as visual saccadic suppression. Saccades also interfere with cognitive processes that are related to vision, such as iconic memory processes.

Founding researchers
Laura E. Thomas and David E. Irwin, researchers at the University of Illinois, were the first to observe, identify, and name cognitive blink suppression as a phenomenon. They proposed that blinking shares some of the same effects on visuospatial cognition as saccadic eye movements, since the two are neurologically similar. By administering a memory task in which participants had to memorize an array of letters, the researchers observed that blinking after the array was shown negatively affected participants' ability to recall where each letter was on the array. To ensure that blinking was the specific cause of this effect and not just any unrelated action, participants in non-blink conditions were asked to press a button after the array was shown. Pressing a button did not negatively affect iconic memory. Blinking appears to affect the way people commit icons to memory, namely what they are and where they can be found.

Current Research and Applications
Recent research has investigated various possibilities as to why blinking so excessively, beyond what is necessary for ocular health, has developed in humans. Some studies have suggested that blinking allows people to briefly disengage from attentional tasks by reducing activity in some parts of the brain and activating the default-mode network. This presumably allows people to stop and gather their thoughts before proceeding to take in further information. However, as these studies are very recent, they must be replicated in more general situations with larger populations before the explanations they provide can be more widely supported.

Studies in vision science have investigated whether increased cognitive load contributes to asthenopia, commonly known as eye strain. Asthenopia is often associated with visual stress rather than cognitive stress, but it appears that cognitive stressors have a similar effect on eye strain. As many patients suffer from asthenopia, cognitive science and psychology have the potential to provide some physical relief with research into alleviating stressful cognitive loads.

As well, research into blinking and thinking has investigated people with autism spectrum disorders, who blink less frequently and don’t engage in synchronized blinking with others. Adults without autism spectrum disorders unconsciously synchronize their blinking with the people they interact with, effectively coordinating their eyeblinks to unconsciously communicate that they are listening. Adults with autism spectrum disorders did not show this pattern, likely because of the characteristic social impairments of individuals with autism spectrum disorders.

Future Research
Given what is currently known about the relationship between blinking and cognition, further research may be able to evaluate the implications of how blinking affects on autism research. It is possible that individuals with autism spectrum disorders are processing the speaker’s face abnormally. In addition, the general blinking patterns in general of people with autism spectrum disorders may provide insight into their cognitive processes and the likelihood that they will be interrupted. Research has begun in this area, studying toddlers with autism spectrum disorders alongside developmentally normal toddlers. Typical children are able to predict emotional moments and blink in anticipation of them, indicating that they are able to follow the story, whereas autistic children do not adjust their blinking patterns. However, they do show a response to actions and movements, confirming that autistic children are better able to track action than emotion. Future eyeblink studies could reveal more about the cognitive processes of autistic children.

Limitations
Most studies in this area have assessed cognition with accuracy on a specific cognitive task, such as a memory or fixation test. Generalizing these results to other types of processes while maintaining a defined causal relationship has been more difficult. For example, when trying to assess reaction times as a measure of cognition, it is unclear whether it is the blink itself or the general irrelevant response of blinking in addition to their primary task that causes the disruption in cognition. In iconic memory studies, a button press did not interfere with cognition, but it does seem to affect participants in reaction time studies. There is currently no conclusive and definite proof, therefore, that this effect is unique to blinking alone, particularly in some domains of cognitive processing.