What Repetition Blindness Means

Have you ever had this happen to you? You've spent weeks working on a research paper and have proofread it multiple times before handing it in for grading. When your instructor returns your paper, you discover that you made a mistake and repeated the words "the the" in a sentence resulting in points lost over a simple editing error.

Frustrating, isn't it? This type of mistake is actually surprisingly common in what is known as a rapid serial visual presentation display, most often lists of words and sentences. In certain instances, people are actually remarkably poor at detecting repetitions. This failure to a second instance of the same thing in a series of words or images is known as repetition blindness.

For example, read the following:

I love Paris in the

the Spring.

Did you spot the second instance of the word the? These repetitions slip by us far too often, but why do we so frequently fail to spot two instances of the same word or image?

What exactly causes repetition blindness? A few different explanations have been suggested. One of the most basic accounts for repetition blindness is that the second occurrence of the word is not recognized as a distinct event, so the second word essentially become assimilated with the first occurrence of the word. For example, in the sentence "she ate the noodles and chicken even though the noodles were undercooked," many participants would show very poor recall of the second instance of the word "noodles."

Some of the more prominent theories to explain repetition blindness:

• Researcher Nancy Kanwisher proposes that the phenomenon is the result of a perceptual problem often referred to as the 'types and tokens' hypothesis. According to this approach, each stimulus in a sequence is recognized by the instance (token) of a category (type). When the same stimulus is repeated, it is identified by type but not tokenized. Because of this, the second appearance of an item is quickly lost from short-term memory before it can be recognized.
• Fagot and Pashler, on the other hand, argue that repetition blindness is the result of memory-retrieval failure. In one experiment, they found that observers displayed repetition blindness for the second occurrence of a letter if subjects attempted to repeat the letters in the order of presentation. This effect disappeared if the participants repeated the letters in reverse order.
• Other researchers including Whittlesea suggest that poor encoding cues lead to an inability to accurately reconstruct a sequence.

"Repetition blindness not only causes observers to miss words or letters, it can also cause observers to create illusory words. For example, if the words lake, brake, and ush are presented rapidly, one after another, for about 100 msec with a 15 to 39 msec break between the words, observers report seeing lake and brush and are astonished when told that brush was never presented." (Revlin, 2013)

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