he and his friends searching. how accurate is eyewitness testimony? how science shows our memories and powers of perception are far less reliable than we believe. a whole host of factors that influence what we see from stress to time, even suggestibility. in fact, psychologist has been able to recreate what the impact of distance is. for example, if you were standing about 50 feet away from me, this is what i would look like. at 100 feet, though, i would look something like this. at 200 feet like this. you get the idea here. 400 feet i'm pretty much unidentifiable. even when we're up close, our minds aren't always as perspective as we think they are. we set up an experiment at the cnn center with my good friend and colleague elizabeth cohen getting ready to tape a story in the food court. in the middle there's an interruption. when we asked bystanders what they noticed, it surprised us what they saw. >> the woman looked a little upset. >> she had like a red colored looking dress. >> she was wearing a two-piece suit. >> i think it was brown or blue maybe. i'm not sure. not sure. >> the perpetrator is my producer trisha. if you were paying attention you would have noticed her big goofy glasses and a black dress and purple sweater. very fascinating. joining me to talk about it more, author of "incognito the secret lives of the brain." welcome back to the show, david, good to have you. >> good to be here sanjay. >> what did you think of that scenario we showed there. interruption as elizabeth was doing her piece. people had a hard time identifying specifics. what did you make of that? >> well, this is very typical. this is always what happens with eyewitness testimony, if you have a crowd, people's perception are aren't reliable. their memory of what they saw tends to drift around. this has been a problem. there are probably 2,000 papers in the cognitive science literature on the unreliability of eyewitness testimony. >> in fact, you've said it's some of the worst technology in use in courtrooms. you think of eyewitness testimony, you think if you have an eyewitness that's going to pretty much seal the deal. you're saying no so fast? >> well, yeah. that's the interest part is that it does seal the deal. for jurors it is extraordinarily swaying for someone to say, look, i don't know about all that other stuff but i know what i saw and i saw this with my own eyes that has an incredible amount of sway on jurors. the reason it's the worst technology in the courtroom, because when you compare it to the other sorts of techniques allowed to be introduced into courts, those go through strict verification processes. there's debate whether they should be allowed in the courtroom, for example, neuroimaging evidence. when it comes to eyewitness testimony, that gets a free pass where everybody assumes it's probably pretty good, and it's not. >> you look at something with your eyes, your brain is processing it, your seeing with your mind. your brain is making decisions on what is necessary to see. how does the brain make that? even with elizabeth and trisha there, how is the brain deciding to focus on one thing and ignore something obvious. what factors come into play there? >> really all we ever see is our internal models of what we think is out there. if you think oh, there's a person and there's some interference, part of it is the data coming between these two holes in your skull but a lot of it is what you believe you're seeing. this is how magic tricks work of it's very easy to have your attention pulled in one place or the other. you believe you've seen something even though what happened right in front of your place is something else. >> this is coming before the supreme court and this is your area. if you were giving advice or testifying, is there a way to quantify how reliable eyewitness testimony is or how well somebody remembered something in terms of how correct it was? >> now, in the legal system, the only way we can estimate this is by looking at, for example, the number of exxonerations that have happened based on dna evidence and then look at how many of those people were actually convicted based in whole or part on eyewitness testimony. what you find is that the vast majority of them had eyewitne eyewitnesses in the case that said i know that's the guy. i'm 100% sure that's the guy who did it and that's the one i saw. in fact we find out later they were exonerated. the numbers are 190 out of 250 exonerated cases relied on eyewitness testimony. >> it's amazing. you and i very in to neurosciences, the tricks that can be played on brains and minds, you delve spoke this stuff, great to speak to you. leather jacket, blue shirt, ring on left finger and mike on your lapel right here. right? got it. >> yes, that's right. >> i think you wore that jacket the last time we spoke as well. that could be my mind playing tricks. i don't know. >> no, it's the same jacket, different shirt. thank you, sanjay. >> hope to have you back again soon. i want to introduce you to ashley smith. she's a young woman and she suffers from paranoid ski schizophrenia. it's a mental illness we don't talk about enough. she's determined to not let her troubles get in the way of her dreams. >> i heard voices, so images of people following me that scared me. >> ashley smith knows what it's like to nearly lose it all. >> i thought my life was in danger. i felt like family members and strangers on the street were against me. >> when she was in college her insanity started slipping away. >> i thought everyone was against me. >> overwhelmed ashley blamed it on stress. >> i would pray a lot about it. i thought if i just continued to cope with it the best way i knew how, i would get through it. >> she didn't. ashley stole a military truck and led police on a high-speed chase. she ended up in jail. two months went by before ashley received a diagnosis of paranoid schizophrenia along with treatment. national alliance says 2 million americans have schizophrenia, in the african-american community it is often misunderstood and not discussed. ashley did something remarkable. she decided to be open about her diagnosis to help others. >> do i look like a person with schizophrenia? >> today she helps train law enforcement officers. they are trained on symptoms. she started a nonprofit organization, embracing my mind, which helps low income and homeless people with mental illness get help. she is studying to be a therapist. >> it's a lifelong process to overcome schizophrenia. i do it through my medication, my support network, which is my treatment team and peers and family. >> ashley hopes sharing her story will reduce stigma surrounding mental health. >> those newly diagnosed or struggling with illness. i say there are going to be ups and downs and very manageable and you can succeed. >> schizophrenia, in case you're wondering, typically appears for the first time in someone's 20s or 30s. still ahead, you'll meet another gupta, no relation to me, who needs your help. progresso. it fits! fantastic! 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[ male announcer ] new glucerna hunger smart. a smart way to help manage hunger and diabetes. leukemia is a word no one wants to hear. the young man i'm about to introduce you to is diagnosed with it. a type of cancer that starts in bone marrow. he needs a transplant, he needs it soon. opportunity for survival is about 35%. a match would double survival. minorities are severely underrepresented in the donor pool. the odds of finding a perfect match are without one in 20,000. ahmed gupta joins us from woodbridge, connecticut. i should point out we have the last night. we are not related but i've been hearing so much about you on social media, facebook and tweets. let me ask, how are you doing? you just finished chemo a few days ago? >> a couple weeks ago. i'm doing well. i start my next round in about a week. this the best i'll feel for the next six months or so. >> right. when you're going through it or immediately after, how tough is it for you? >> towards the end it gets kind of rough. there's a lot of mouth symptoms and just fatigue. it gets tough. >> you're barely 30 years old. before all this, you were perfectly healthy, you never had a problem or any health problems to speak of. >> yeah, not really. >> so what happened? when did you first notice you weren't feeling well and it was serious? >> i think early in september i just started feeling tired a lot. other than that, i just had a couple other things like i spiked a fever one weekend. bright lights started looking really bright. random things. i went to see my daughter, one thing led to another and he told me i had leukemia. >> a tough question to ask. you're a young guy. you hear news like this. what goes through your mind? >> it just felt so unfair. honestly i think i cried more in that first week than i have in my entire life. spent a lot of time feeling sorry for myself, which isn't something i'm proud of but it was a hard week. >> i think anybody would completely understand that, myself included. so you're an entrepreneur. you're someone who has had success in this world. at some point do you say, okay, let me try and use my skills to try and do something for myself and for people who like me? >> yeah. there's lots of different ways. we haven't really used other types of media besides social media so far and we went from having two drives, one planned for my friends in new york and another in san francisco to having 30, 40, 50 drives across the united states, some australia, some canada. the national marrow donor program told us they have had higher traffic to their site in the past two weeks than they have ever had in the past. we actually brought the site down the first day we started talking about this. >> is that right? the registry for bone marrow went down because of this. what we're talking about here is drives to try and register people to become bone marrow donors. >> that's right. >> what does that mean? can you explain what the process is for someone to do that? >> sure. it's pretty easy. basically, it's much more difficult than a blood match test. they need to get people in and rental sister in case you end up matching someone someday. what you do, give you a couple swabs, q tips, you rub the inside of your mouth gently with q-tip and they do a dna typing on that to see if you're a match for someone. >> to be clear, i'm in the bone marrow registry because i did exactly what you described, and i'm in the registry. one thing that strikes me as well when i talk to people about this. they worry if they become -- this is an apprehension. if they are a donor, it's going to involve a painful procedure to give bone marrow to transplant. that causes anxiety. let's say if you and i were a match. i was called and they said you're a match for him, what would that be asking of me? >> basically what they do, they do a thorough health test. there's no cost to you for any of this. they do a thorough health test. they make sure you are healthy and able to donate. a few days before my transplant is supposed to happen, they would give medications you would overproduce your bone marrow cells and they would spill over into your blood. the process of actually harvesting those bone marrow cells is similar to giving blood. they basically hook you up to a line in one arm and a line in another and they are able to filter the bone marrow out without a needle or invasive procedure. >> it's important to hear, life giving blood to try to provide bone marrow for someone like amit. i hope this helps. i hope people are watching and hear your story and want to help you. it's really not that hard, and for a lot of other people as well. thanks for joining us. we'll keep in touch, keep tabs. thank you for joining us. >> thank you so much. >> if you want to help out amit, check out his website. there's information about upcoming drives and information about becoming a donor as well. keep tabs on him, post a link on my life stream @cnn gupta. finding happiness, something we can all learn. you're not going to want to miss this. what's this? 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[ male announcer ] progresso. you gotta taste this soup. you know, the world health organization presix.ducts that in less than 20 years, depression will be the second most widespread ill inspect world behind only hiv/aids. even now in any given year, one in ten americans suffers from a mood disorder it makes you wonder exact what i is happening here and who can help us understand this better than dr. andrew while, wrote a new book called "spontaneous happiness" which offers a few ideas. thanks for joining us again. you and very gotten know each other over the years and i have to say when i started reading this book, some of this surprised me just about you, this is something you haven't shared your own struggles with depression. first of all, you are doing well now, right? >> this was in my 20s, 30s and 40s, mostly. as i have gotten older, it has receded. i think some of that may have to do with getting old and a lot has to do with lifestyle changes i have made i wanted to share that information. i never had major depression. >> what was it like for you. >> there were many days, periods where more days than not, i was just feeling in a blue mood. i often didn't feel like getting out of bed and doing things. i would go ruminate about feelings of worthlessness and i also found i withheld myself from social interaction when i was in that state, which is probably one of the worst things i could do, because scientific research says social interaction is strongly protective against depression. >> you have -- people know who you are, know some of the things you stand for in the world of medicine and health what did you do at that time, years ago, for your own depression? >> i tried various forms of psychotherapy, filled a prescrin for zoloft and stopped, it made me feel terrible it made my body feel bad and it numbed my mind and i decided maybe this is something i have to live with it is existential and a sort of feeling somehow my creativity was linked to these periods. i have talked about that in the book there is a striking correlation between creativity, artistic success, literary success and depression. there is a very interesting new idea of depression that comes out of evolutionary psychology, suggesting that we may be programmed to be depressed because it's a state of inward focus and rumination maybe the way we solve problems. so, there may be a value in experiencing depression, as long as it is not overpowering. at any rate, as i say, i made a loft changes in my life in midlife, one of them was becoming more physically active. another was taking regular doses of fish oil and eating oily fish. getting my vitamin d levels to the right level. >> some of these things because of you myself. >> good. good. good. but then i became very flood meditation, and technique of eastern psychology for managing thoughtsism think, for most of us, thoughts are usually the source of sadness, anxiety, fear and a real challenge to learn how to do that one way is by improving attention and doing meditative practice. >> were you doing this to try to stave off your depression or something you were learning about simultaneously? >> i think it was bothism knew that would be good thing for know do over the years that practice has been very valuable to me. i rarely have -- i rarely experience depression today. and even when bad things happen to me or i have to deal with bad situations, i think i bounce back from them pretty quickly. that kind of resilience is something that can be cultivated. >> you have been productive your whole life, seemingly, but this had idea that you're more creative in these periods were you're blue or you're -- >> not necessarily in the periods but coming out of them -- >> i see. >> seems like i dip into some well and get ideas and thoughts. i just had had a sense had that that was so. >> you come out with some burst of productivity? >> exactly right. >> medication -- and your views on a lot of medications are pretty well known but for people thought listening who have serious depression, a serious illness here what do you tell them? >> severe depression is a severe illness and that needs to be managed professionally. the use of medication may be important. i would never tell anybody to stopped me cation if they are bipolar. is there growing scientific of evidence, ssris, most popular anti-depresents are not that good. data showing for most cases they work no better for placebos, certainly in mild to moderate depression. they are not benign, they have toxic effects. the most problem recently cited is they create their own need, when you increase serotonin at neural junctions, the body responds,logically, by making less serotonin and dropping receptors and it becomes very hard to get off this is called the tarttive disfor ya, a lingering depression caused by the drugs f people want to use these it might be good to use them for lame mitted period and figure out other things you can be do and get off them. >> always fascinating to speak with you, and i'm glad you're well. >> thanks. >> congratulations on the book. >> take care of yourself, don't tour too much. and we will be right back with a good laugh. i promise. stay with us. glucerna shakes. like they have slowly digestible carbs to help minimize blood sugar spikes, which can help lower a1c. 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[ male announcer ] ask your doctor if cialis for daily use is right for you. for a 30-tablet free trial offer, go to cialis.com. last but not least this morning, i tell you this all the time, but laughter is the best medicine. here is a bit of "the "daily show"" from hall weechblt as it turns out, at my oaks spence. >> i wanted to come as you, i thought that would be a funny costume. i s