"Long before it's in the papers"
January 27, 2015


Study: Your brain sees things you don’t

Nov. 14, 2013
Courtesy of the University of Arizona
and World Science staff

The brain pro­cesses and un­der­stands vis­u­al in­put that we may nev­er con­sciously per­ceive, a study sug­gests.

The find­ing chal­lenges cur­rent views on how the brain pro­cesses vis­u­al in­forma­t­ion, said Uni­vers­ity of Ar­i­zo­na doc­tor­al de­gree can­di­date Jay San­guinetti, who au­thored the stu­dy. It is pub­lished on­line in the jour­nal Psy­cho­log­i­cal Sci­ence

San­guinetti showed study par­tic­i­pants im­ages of what ap­peared to be an ab­stract black ob­ject. Some­times, how­ev­er, there were real-world ob­jects hid­den at the bor­ders of the black sil­hou­ette. In this im­age, the out­lines of two sea­horses can be seen in the white spaces sur­round­ing the black ob­ject. (Cred­it: Jay San­guinetti )

San­gui­netti showed study par­ti­ci­pants a se­ries of black sil­hou­ettes, some of which con­tained real-world ob­jects hid­den in the white spaces on the out­side. He worked with psy­chol­o­gists at the uni­vers­ity to mon­i­tor peo­ple’s brain­waves while they viewed the ob­jects.

“We were ask­ing the ques­tion of wheth­er the brain was pro­cess­ing the mean­ing of the ob­jects that are on the out­side of these sil­hou­ettes,” San­gui­netti said. “The spe­cif­ic ques­tion was, ‘Does the brain pro­cess those hid­den shapes to the lev­el of mean­ing, even when the sub­ject does­n’t con­sciously see them?”

The an­swer, he added, seems to be yes. Study par­ti­ci­pants’ brain­waves in­di­cat­ed that even if a per­son nev­er con­sciously rec­og­nized the shapes on the out­side of the im­age, their brains still pro­cessed those shapes to the lev­el of un­der­stand­ing their mean­ing.

“There’s a brain sig­na­ture for mean­ingful pro­cess­ing,” San­gui­netti said. A peak in the av­er­aged brain­waves called N400 in­di­cates that the brain has rec­og­nized an ob­ject and as­so­ci­at­ed it with a par­tic­u­lar mean­ing, he ex­plained.

“It hap­pens about 400 mil­lisec­onds af­ter the im­age is shown, less than a half a sec­ond,” said Mary Pe­ter­son, San­gui­netti’s ad­vis­er and di­rec­tor of the uni­vers­ity’s cog­ni­tive sci­ence pro­gram, who worked with him.

“The par­ti­ci­pants in our ex­pe­ri­ments don’t see those shapes on the out­side; none­the­less, the brain sig­na­ture tells us that they have pro­cessed the mean­ing of those shapes,” said Pe­ter­son. “But the brain re­jects them as in­ter­preta­t­ions, and if it re­jects the shapes from con­scious per­cep­tion, then you won’t have any aware­ness of them.”

The find­ing raises the ques­tion of why the brain would pro­cess the mean­ing of a shape when a per­son is ul­ti­mately not go­ing to per­ceive it, San­gui­netti said. “The tra­di­tion­al opin­ion in vi­sion re­search is that this would be waste­ful in terms of re­sources,” he ex­plained. “If you’re not go­ing to ul­ti­mately see the ob­ject on the out­side why would the brain waste all these pro­cess­ing re­sources and pro­cess that im­age up to the lev­el of mean­ing?”

“Many, many the­o­rists as­sume that be­cause it takes a lot of en­er­gy for brain pro­cess­ing, that the brain is only go­ing to spend time pro­cess­ing what you’re ul­ti­mately go­ing to per­ceive,” added Pe­ter­son. “But in fact the brain is de­cid­ing what you’re go­ing to per­ceive, and it’s pro­cess­ing all of the in­forma­t­ion and then it’s de­ter­min­ing what’s the best in­ter­preta­t­ion.”

“This is a win­dow in­to what the brain is do­ing all the time,” Pe­ter­son said. “It’s al­ways sift­ing through a va­ri­e­ty of pos­si­bil­i­ties and find­ing the best in­ter­preta­t­ion for what’s out there. And the best in­ter­preta­t­ion may vary with the situa­t­ion.”

Our brains may have evolved to sift through the bar­rage of vis­u­al in­put in our eyes and iden­ti­fy those things that are most im­por­tant for us to con­sciously per­ceive, such as a threat or re­sources such as food, Pe­ter­son sug­gested. In the fu­ture, Pe­ter­son and San­guinetti plan to look for the spe­cif­ic re­gions in the brain where the pro­cess­ing of mean­ing oc­curs.

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The brain processes and understands visual input that we may never consciously perceive, a study suggests. The finding challenges current views on how the brain processes visual information, said University of Arizona doctoral degree candidate Jay Sanguinetti, who authored the study. It is published online in the journal Psychological Science. Sanguinetti showed study participants a series of black silhouettes, some of which contained real-world objects hidden in the white spaces on the outsides. He worked with psychologists at the university to monitor people’s brainwaves while they viewed the objects. “We were asking the question of whether the brain was processing the meaning of the objects that are on the outside of these silhouettes,” Sanguinetti said. “The specific question was, ‘Does the brain process those hidden shapes to the level of meaning, even when the subject doesn’t consciously see them?” The answer, he added, seems to be yes. Study participants’ brainwaves indicated that even if a person never consciously recognized the shapes on the outside of the image, their brains still processed those shapes to the level of understanding their meaning. “There’s a brain signature for meaningful processing,” Sanguinetti said. A peak in the averaged brainwaves called N400 indicates that the brain has recognized an object and associated it with a particular meaning, he explained. “It happens about 400 milliseconds after the image is shown, less than a half a second,” said Mary Peterson, Sanguinetti’s adviser and director of the university’s cognitive science program, who worked with him. “The participants in our experiments don’t see those shapes on the outside; nonetheless, the brain signature tells us that they have processed the meaning of those shapes,” said Peterson. “But the brain rejects them as interpretations, and if it rejects the shapes from conscious perception, then you won’t have any awareness of them.” The finding raises the question of why the brain would process the meaning of a shape when a person is ultimately not going to perceive it, Sanguinetti said. “The traditional opinion in vision research is that this would be wasteful in terms of resources,” he explained. “If you’re not going to ultimately see the object on the outside why would the brain waste all these processing resources and process that image up to the level of meaning?” “Many, many theorists assume that because it takes a lot of energy for brain processing, that the brain is only going to spend time processing what you’re ultimately going to perceive,” added Peterson. “But in fact the brain is deciding what you’re going to perceive, and it’s processing all of the information and then it’s determining what’s the best interpretation.” “This is a window into what the brain is doing all the time,” Peterson said. “It’s always sifting through a variety of possibilities and finding the best interpretation for what’s out there. And the best interpretation may vary with the situation.” Our brains may have evolved to sift through the barrage of visual input in our eyes and identify those things that are most important for us to consciously perceive, such as a threat or resources such as food, Peterson suggested. In the future, Peterson and Sanguinetti plan to look for the specific regions in the brain where the processing of meaning occurs.