steven pinker is the author of the book "better angels of our nature." dr. death than any other point in history. you spend six chapters. give me the cliffs notes version now if you would. >> violence has declined on many scales of time and magnitude. homicide is down compared to centuries ago. wars are less common and deadly. domestic violence is down. racial minority violence is down. people spank their kids less than they used to. any way you want to measure violence, the trend is downward. >> even when you control for war, that trend has been downward? >> that is right. most dramatically since the end of world war ii. when the most destructive kind of war, when you have two big rich countries fighting each other, has almost disappeared off the map. for most of history, the 800-pound gore wiillas were at other's throats. since 1953, big countries stay out of each other's faces. >> what accounts for the long piece in your book? >> the world is more connected. countries trade with each other and it becomes cheaper to buy things than to plunder them. there i

it is hard to imagine where you would have the two pinkers.re are two block boxes. >> so let me ask you about the pinging deviced and at this point you are not sure if your deviced were dispatches to that aircraft or were in those black boxes but i found it iraq lus to suggest that we could have black boxes that could ping for years. can you explain that? >> so the way it works. this is our 30 day pinger. this is what we use right now. this is not the wuone that is i the plane that we are talking about. as so as soon as it hits the water it emits that sing nal. these are used on air frames they are new going into the market. this is going to be active for 90 days. the difference in price is $100. those technologies as soon as they hit the water you have the sound and the reality is to get longer life time. so the listening device or the active seeker sends a signal out and we make these all the time and it is a common instrument to put into the ocean. this is a thing we call an under water trance ponder. you can go all the way up to something

think there are a lot of reasons to believe this is a false positive and it didn't correlate to the pinker oig from the aircraft. it would have been an incredible stroke of luck if it were. it's interesting the length the australi australian authorities are going as if it is. >> if they don't ever detect any pings again, do you stay confident this is the area where it was from the black poxes and how do you deal with the search? >> well, you have to deal with it exactly what the australia krans are doing. and they're doing the right thing. whether this were -- this is all they have right now, so if they never hear the pings again, they literally have to throw everything at it. this shall the last best hope. so they he have to make certain they have exhausted all possible avenues for the sake of aviation safety and security, but also for the sake of the families. so if there is anyway to find anything in the area where they heard this acoustic event, that's what they have to do and fortunately that's what they're doing. >> in a nugget, explain what you mean by the false positives, jeff. >>

i'm just talking about the pinkers oig now. floating debris is another issue. >> let's get to the floating debris later. let's stick with the pingers for now yet. >> a lot of false positives on the float dag bring debris. but they would accepted the aircraft into help verify this independently of the ship. and then i would imagine they would move in the tow locaters. those are much more accurate as you probably hoe. they can go to great depths. and the pingers don't have a tremendous range. you want to find out exactly where it's at so you can send in the robotic subs with their live scan sonar to try to map the wreck alleage pattern and then probably followed by robotic photographic devices to photograph the wreck. and then they would go after the recorders first after they find those, make the decision what they want to bring up. obviously they want to recover as much as they can first of all to recover the human remains just out of respect to the families. but they may not -- about this is very deep water, they may decide af

the batteries that run the pinkers, only r only good for about 30 days.y would go silent any day now. >>> it has been 31 days since the jet liner disappeared. many of the families are still hoping for answer. >> reporter: it began with the inexplicable failure of the flight to arrive at beijing airport. hundreds of relatives who had never met suddenly became the center of a media frenzy. in the coming days there would be torment, also anger at the alleged withholding of information by officials, and even a protest in front of the malaysian embassy. that's why we went to the embassy, because we just want to find the news. >> reporter: steve has become the spokesman for the relatives. >> we're just sitting on a roller coaster, and we are exhausted mentally. >> reporter: as the days turned into weeks, this hotel has become home for many relatives like this woman who's grand parents were on the flight. >> translator: we reached the consensus that we can only wait quietly for definite news. >> reporter: several hundred of the relatives are still here. in the a

because they're hearing pinkers, what they believe two different signals from far away, it done mean that. two miles, three miles but that's the minimum range? >> that's what the faa does, set the minimum standards. we don't set the maximum standards. >> you're thinking that they're within two or three miles. >> it makes it much harder. it's 160 dessiabilities, as loud as a gunshot, it's the gunshot at frequency of a dog wising. humans can't hear it. that's how loud it is under water. think about being in the mountains and hear a gunshot and trace down where that gunshot went, not an easy thing to do. >> les abend, where do you think most of the assets should be devoted, air or sea? >> i think continue assets in both directions, in the sea and on the air because -- on the water because i think those fragments debris fragments are important to locate just by beginning, you'll agree with me, i think, david, first part of the investigation process and of course we know how important the black box. >> who was it, miles you said in another show, they're not going to hear pingers and start

. >> when you look at the graphic, i think you can see where the ship was or the pinker was -- pinger doesn't mean that is where the plane was -- >> why is it spread out? because sound bounces around on the water? >> exactly, sound bounces around, and depending on where the tpl is, the sound, it depends on where they go, with the layers and the topography. >> that is why they're getting the opportunity to hear more pings -- >> it would be like standing up on the mountains in the colorado mountains, shouting, you hear the echo go out, sometime it goes over the mountains, you could be standing on the rock on the other side and not hear that shout. that is kind of what is going on. that is how you get it closer, saying that is an echo, a refracted area -- >> how long do you think they will continue with the pinger locater? because we know -- 30 days is supposedly the life span of this thing. i talked to i think it was captain matthews who said we'll maybe give it as much as 45 days just in case. >> yeah, i think when we were talking to matthews at that time, he referred to mostly saying

. >> reporter: the ocean shield is pulling a towed pinker and it's described the way you would mow our lawn. martha: why aren't they using remote controlled submarines to look for this wreckage? >> reporter: investigators know they heard pings this weekend and now they don't hear them. they don't know if there is even a black box down there at all. >> there have been no further contacts with any transmission and we need to continue that for several days right up to when -- the point at which there is absolutely no doubt that the pinger batteries will have expired. so it will be several days more. until we stop the pinger search, we'll not demoistur -- we'll noy the submersible. >> they should be able a hear a ping one mile in each direction. martha: the depth is something to be contended with in this whole situation. bill: a pretty good depiction on the map. that's the ocean shield, the australian vessel that trolls on the top of the ocean floor. upwards of 3 miles deep in this part of the indian ocean. this is the cable that stretches down. based on the information we have that cable

one day's work for the pinker o oig locater would take a full week for the submersible. don't find a seg natura signal, the search effort will get much slower. >> will, we appreciate it. each new lead sounds promising, but ends in dashed hopes. let's talk about that. an social search specialist and a company that produces advanced underwater communications systems joins us pull welcome, gentlemen. >> good morning. >> is it surprising that searchers koochcouldn't pick up anymore pings? >> it's disappointing, but not surprising. we've all learned a lot about debris. now we're learning about underwater acoustics. we're learning that sound when it's traveling through water does not travel like sound through air. it's bent by temperature, bylen factors. >> does the absence of any new pings mean necessarily that the batteries are dead on the black boxes? >> absolutely not. first of all, the pink ee ee ees have a margin. they last a minimum of 30 days. so the life time is dependent on a lot of other parameter, how it was handled, how it was stored. it could be much longer than