聞聲識(shí)海豚

文 / 薩拉·普拉托（意大利） 譯 / 楊云舟

我從小就十分喜愛小動(dòng)物，身邊一直有小動(dòng)物陪伴。長(zhǎng)大之后，這份對(duì)動(dòng)物的親昵之情自然而然地讓我萌生了從事獸醫(yī)職業(yè)的想法。不過，我的父母一開始對(duì)此表示反對(duì)，他們始終希望我能去攻讀像法學(xué)一類的實(shí)用學(xué)位。但憑借著堅(jiān)持不懈的努力，我最終說(shuō)服了父母。也正是因?yàn)檫@份堅(jiān)持，我最終說(shuō)服了獸醫(yī)學(xué)教授允許我前去加納利群島旅行。在研究獸醫(yī)學(xué)的日子里，海豚這種動(dòng)物引起了我極大的興趣，而加納利群島廣闊的海岸能為我?guī)?lái)與海豚親密接觸的豐富機(jī)會(huì)。

在海島上，我花了很多時(shí)間來(lái)研究動(dòng)物們的行為，時(shí)不時(shí)還會(huì)向它們提供一些幫助。不過我知道，自己想要的不僅是這些。我希望能夠了解動(dòng)物之間的交流方式。當(dāng)還只有5歲的時(shí)候，我就有了第一次與動(dòng)物交流的經(jīng)驗(yàn)。通過模仿母貓的聲音，我成功地把小貓從藏身處哄出來(lái)一起玩耍。于是，在一位德國(guó)教授的幫助下，當(dāng)時(shí)還是學(xué)生的我從加納利群島搬到了以色列，繼續(xù)進(jìn)行著海豚研究。海豚和海豚之間——以及海豚與人類之間——究竟是如何互動(dòng)的？它們用什么方法來(lái)交流？它們又是如何傳達(dá)自己需求的呢？與此同時(shí)，我一直沒有忘記自己的另一個(gè)追求：為那些需要照料的動(dòng)物提供幫助。我曾前往美國(guó)和加拿大的多家機(jī)構(gòu)，與那里的工作人員一起為海洋動(dòng)物和其他動(dòng)物朋友們提供醫(yī)療和保護(hù)上的援助。

在這之后，2007年，我來(lái)到了中國(guó)，開始著手進(jìn)行博士后研究。自2017年開始到現(xiàn)在，我一直在江漢大學(xué)任教。

奇妙的海豚和奇妙的聲音

海豚和人類都是社會(huì)性哺乳動(dòng)物，都有著非常相似的社會(huì)結(jié)構(gòu)，即“裂變—融合社會(huì)”。什么叫裂變—融合社會(huì)呢？這其實(shí)指的是由不同個(gè)體組成的小家庭作為社會(huì)單位又組成了社會(huì)。一個(gè)裂變—融合社會(huì)中的家庭成員在各自的日常生活中都會(huì)有很多事情要分頭處理。例如，人類要上班，海豚則要出去捕食。我們每個(gè)人都會(huì)離開家庭去 做各自的事情，但是到了最后，大家又會(huì)聚在一起。但人類和海豚又大有不同。我們生活在不同的環(huán)境中，也因此進(jìn)化出了不同的感官系統(tǒng)來(lái)適應(yīng)環(huán)境。生活在堅(jiān)實(shí)的陸地上的我們有著獨(dú)特的大腦構(gòu)成，海豚的大腦則與我們的不同。不過，盡管有這樣那樣的差異，人類和海豚在小社會(huì)或大社會(huì)中卻都有著共同的交流需求。

薩拉·普拉托（Sara Platto，意大利），江漢大學(xué)生命科學(xué)學(xué)院副教授，中國(guó)生物多樣性保護(hù)與綠色發(fā)展基金會(huì)生物與科學(xué)倫理秘書長(zhǎng)。普拉托博士在動(dòng)物福利、動(dòng)物行為、野生動(dòng)物病理學(xué)等方面都有著研究貢獻(xiàn)。

像海豚一樣在海底生活和交流可能會(huì)面臨著不少的挑戰(zhàn)。其中一個(gè)挑戰(zhàn)就是視覺能力。深海環(huán)境中的海水模糊不清，四周一片漆黑，幾乎沒有任何光線能到達(dá)這里。而就算在海水尚還清澈的地方，可見光也只能到達(dá)海平面以下100米處的深度。更何況，大海里還常常有海浪的干擾和海草等障礙物的阻擋。所以，我們?cè)诤Ｃ嫦潞苡锌赡苤荒芸吹綆酌?，甚至幾厘米開外的東西。這樣一看，視覺感官似乎對(duì)于海洋動(dòng)物來(lái)說(shuō)并沒有那么大的作用。但是，如果海豚的視力如此之差，它們又是怎么能夠如此自在地游來(lái)游去，和其他海豚交朋友，還要躲避其他捕食者的呢？它們要利用什么感官呢？答案就是——聲音！

聲音在海水中的傳播速度受到多種因素的影響。由于水和空氣的密度不同，聲音在海平面以下的傳播速度是在海平面以上時(shí)的4.5倍。除此之外，聲音的傳播速度還與海水的溫度和鹽度有關(guān)。水溫越高、海水越咸，聲音的傳播速度就越快。還有，海洋深處的水壓明顯高于海面，而此時(shí)聲音的傳播速度也會(huì)相應(yīng)加快。

我們?cè)谒镆材苈牭铰曇?。但海豚的聽力和我們一樣嗎？遺憾的是，由于人類耳朵的形狀和結(jié)構(gòu)，我們?cè)谒兄荒芙邮盏接邢薜穆曇纛l率范圍。出于同樣的原因，我們?cè)谟斡緯r(shí)雙耳也無(wú)法辨別聲音的方向。那海豚呢？它們?cè)谒械穆犛X能力要先進(jìn)得多，因?yàn)樗鼈儾幌袢祟悺祟愔荒芙邮?0Hz—15kHz的頻率，而海豚可以接收75Hz—150kHz的所有聲音頻率。

那么，海豚是如何發(fā)聲的？我們?nèi)祟愑寐晭?lái)發(fā)聲，而海豚則采用了另一種方法——它們通過自己鼻腔的器官發(fā)聲，這個(gè)鼻腔器官位于額隆部位（海豚頭頂?shù)膱A形部分）。空氣會(huì)通過海豚的呼吸孔進(jìn)入一個(gè)類似口袋狀的結(jié)構(gòu)中，一旦這個(gè)口袋狀的結(jié)構(gòu)發(fā)生震動(dòng)，就會(huì)產(chǎn)生聲音。但除了這一部分的器官，海豚還有另外的非常重要的發(fā)聲裝置——它們體內(nèi)的兩套唇狀器官。這兩個(gè)聲唇使它們能夠同時(shí)發(fā)出兩種聲音：既可以發(fā)出用來(lái)交流的哨聲，也可以發(fā)出用來(lái)掃描環(huán)境的定位回聲。

這些聲音在發(fā)出來(lái)后是怎么被海豚聽到的呢？海豚額隆里的脂肪組織和水的密度是一樣的。這些組織的功能就像一個(gè)透鏡，可以通過改變形狀來(lái)把聲音傳到各個(gè)不同的方向和角度。在海豚的下顎周圍也存在著類似的脂肪組織。當(dāng)聲音傳來(lái)時(shí)，頜骨內(nèi)的脂肪組織就會(huì)感知到它們的震動(dòng)，然后將聲音傳到海豚耳朵的內(nèi)部，而海豚的耳朵也被同樣的脂肪組織所包圍。雖然它們有耳朵，也有耳道，但由于結(jié)構(gòu)與人類不同，海豚在水面上的聽力不如在水下時(shí)的好。

海豚的“聲音百寶箱”

為了能夠更好地了解海豚所發(fā)出的聲音，研究人員將幾種不同模式的聲像圖分離了出來(lái)。從這些不同的聲音模式中，科學(xué)家們能夠辨別出這些聲音發(fā)出時(shí)的場(chǎng)景，如當(dāng)時(shí)海豚的心情怎樣，或者當(dāng)時(shí)它們是在趕路還是在做其他的事。

在海豚發(fā)出的不同聲音里，有一種被稱為“口哨”的聲音，平均頻率范圍在75Hz—24kHz（有時(shí)候會(huì)超過24kHz）。哨聲是全向的，這意味著很難根據(jù)它來(lái)辨別聲音的源頭。一聲哨聲由兩個(gè)部分組成：基礎(chǔ)頻率，即主哨，以及以基礎(chǔ)頻率的整數(shù)倍頻率傳播的諧波，通常都達(dá)到了超聲波（>20kHz）范圍。同時(shí)含有非指向性和指向性成分的哨音被稱為“混合指向”哨音。研究人員發(fā)現(xiàn)，哨聲中的諧波其實(shí)可以用來(lái)進(jìn)行方向追蹤。因此，當(dāng)海豚既要傳達(dá)自己的信息，又要表達(dá)自己的位置時(shí)，就會(huì)同時(shí)釋放出哨聲和諧波。

人都有自己的名字，每個(gè)人都通過對(duì)方的名字來(lái)認(rèn)識(shí)不同的人。海豚也有名字——這就是每只海豚的標(biāo)志性哨音。海豚可以用特定的哨音給自己貼上標(biāo)簽——就像名字一樣——每只海豚都有自己特有的哨音。這種標(biāo)志性哨音也可以被其他海豚模仿，用來(lái)呼喚單獨(dú)某一只海豚，就像我們叫一個(gè)人的名字一樣。

海豚頭部?jī)?nèi)聲音發(fā)收結(jié)構(gòu)示意（繪圖：Vko Gorter）

除了口哨聲外，海豚還有另一種聲音，是用來(lái)回聲定位的“嘀嗒聲”，聽起來(lái)就像木棍互相撞擊的聲音。海豚用這種聲音來(lái)掃描周圍的環(huán)境，尋找食物或障礙物。每一次嘀嗒聲之后都有一個(gè)間隔，在這個(gè)間隔中，海豚會(huì)等待回聲的返回，然后再發(fā)出下一次嘀嗒聲。通過測(cè)量這個(gè)時(shí)間間隔，海豚可以計(jì)算出自己與某個(gè)物體的距離，從而在腦海中繪制出一幅環(huán)境地圖。

海豚還有第3種聲音，叫作“脈沖聲”。脈沖聲包含了情感成分。當(dāng)海豚感到不高興或相互爭(zhēng)吵時(shí)，它們就會(huì)發(fā)出這種聲音?？茖W(xué)家們根據(jù)脈沖聲的細(xì)微不同把這種聲音分成好幾類，如喊聲、哭聲、啜泣聲。不同種類的海豚能夠發(fā)出的聲音其實(shí)不盡相同。例如，無(wú)鰭江豚就只能發(fā)出脈沖聲，而發(fā)不出口哨聲。

海豚感知的世界

人類主要通過視覺和語(yǔ)言來(lái)創(chuàng)造自己的現(xiàn)實(shí)。每當(dāng)看到新的事物，我們就會(huì)忙不迭地給它命名，從而也就認(rèn)識(shí)了它。一般來(lái)說(shuō)，“自我”概念建立的根基是大腦對(duì)如以自我為中心的空間和時(shí)間軸等外部信息的處理，以及頭部、身體的位置和方向等內(nèi)部信息的定位。這些都是構(gòu)建自我的要素。除此之外，記憶、期望、計(jì)劃等只不過是一些附加要素。對(duì)于海豚來(lái)說(shuō)，所有關(guān)于外部世界的信息都來(lái)自回聲定位。

人類在交談時(shí)會(huì)問：“你看到我所看到的了嗎？”或者“你看到我剛剛說(shuō)的了嗎？”海豚則不同，它們會(huì)問：“你看到我剛剛聽到的了嗎？”每當(dāng)海豚通過嘀嗒聲來(lái)回聲定位、掃描周圍的環(huán)境時(shí)，它們就能在大腦中構(gòu)建出一種“全息圖像”。令人驚奇的是，這些回聲可以被附近的另一只海豚接收到，而它們則會(huì)收到完全相同的“全息圖像”！當(dāng)不同的人從不同的角度看同一個(gè)物體時(shí)，他們看到的畫面也自然不一樣。這取決于他們每個(gè)人如何感知他們的現(xiàn)實(shí)?；芈暥ㄎ挥幸粋€(gè)與人類語(yǔ)言截然不同的特征，即在此處，海豚大腦對(duì)現(xiàn)實(shí)的構(gòu)建基于的其實(shí)是個(gè)體所產(chǎn)生的信號(hào)。在從回聲定位構(gòu)建現(xiàn)實(shí)的過程中，海豚可以彼此分享“原始”的感官信息。與我們用語(yǔ)言分享信息相比，這真是不同尋常。這些信息存在于聽覺領(lǐng)域，它們所產(chǎn)生的“物體”圖像就如同人類看到的畫面一樣真實(shí)。這是我們難以想象的。盡管這只是一種推測(cè)，但科學(xué)家認(rèn)為，海豚之間存在一種社會(huì)性或者共同感知的可能性是存在的。事實(shí)上，一個(gè)由共享的原始數(shù)據(jù)構(gòu)建的感知世界將賦予一個(gè)群體以不同尋常的凝聚力和個(gè)體概念。更有趣的是，海豚的感官共享有可能是一個(gè)主動(dòng)的過程，而非純粹被動(dòng)地接收。這就像每個(gè)人都能夠同樣感知到某一個(gè)人所看到的世界的畫面一樣。感官共享的能力將大大改變“自我”的界限，“個(gè)體”的概念也將得到重新定義。

當(dāng)一兩只海豚生病擱淺時(shí)，族群中其他的個(gè)體都會(huì)紛紛相隨

海豚大腦的特殊結(jié)構(gòu)為這一假說(shuō)提供了有力支持。人類的大腦可以劃分出3重主要復(fù)合區(qū)：爬蟲腦復(fù)合區(qū)、邊緣系統(tǒng)和新皮層。然而，在鯨類身上，我們看到了一個(gè)徹底的進(jìn)化跳躍——大腦結(jié)構(gòu)中加入了第4段。這個(gè)部分被稱為副邊緣，位于邊緣系統(tǒng)和新皮層之間，并突入新皮層之中。這種結(jié)構(gòu)只存在于鯨類動(dòng)物的大腦中。鯨類大腦的整個(gè)邊緣系統(tǒng)是用于處理情緒和形成記憶的多個(gè)結(jié)構(gòu)的組合，而副邊緣額葉這一獨(dú)特的進(jìn)化則表明鯨類或許有能力處理更復(fù)雜的思想和情緒。由于鯨類的這一系統(tǒng)非常大，而且獨(dú)特的副額葉又與新皮層雙雙合并，人們認(rèn)為，它們的大腦中可能會(huì)產(chǎn)生出情緒和認(rèn)知思維的混合。副邊緣額葉也被認(rèn)為是感覺區(qū)和運(yùn)動(dòng)區(qū)的延續(xù)。人類大腦中每個(gè)投射區(qū)之間的距離都很遠(yuǎn)，意味著我們從視覺、聲音和本能中接收到的所有信息都必須沿著纖維道一點(diǎn)點(diǎn)傳播到位。這一過程的時(shí)間和信息損失都非常大。鯨類的副邊緣額葉則將所有感官反射集于一身，以我們無(wú)法理解的豐富性和迅速性處理著所有信息。副邊緣系統(tǒng)的獨(dú)特進(jìn)化表明，在共同處理情緒和聲音信息的背后，海豚之間有一些非常精密、復(fù)雜的交流機(jī)制。它們的大腦可能已經(jīng)掌握了一種在動(dòng)物王國(guó)中前所未有的社會(huì)共性。這將把所謂“社會(huì)性”的概念提升到一個(gè)完全不同的層次。而事實(shí)上，海豚在群體層面有著很強(qiáng)的凝聚力，當(dāng)一兩只海豚生病擱淺時(shí)，族群中所有其他的個(gè)體都會(huì)紛紛相隨。這在很大程度上可能是情感依戀的產(chǎn)物，這些動(dòng)物可能有一種強(qiáng)烈的集體意識(shí)。一些科學(xué)家將海豚的這種凝聚力稱為“集體靈魂”。

那么，海豚算得上聰明嗎？它們必須要“像我們一樣”才能稱得上是智慧生物嗎？雖然鯨類動(dòng)物擁有包括人類在內(nèi)的動(dòng)物中最大的大腦，但這并不一定意味著它們比我們智力更高。不過，智力的定義其實(shí)是一個(gè)相當(dāng)模糊的問題。到目前為止，我們還沒有完全了解人類大腦的全部功能，也沒有找到定義智力的準(zhǔn)確標(biāo)準(zhǔn)。我們通常只會(huì)用我們的現(xiàn)實(shí)來(lái)定義其他動(dòng)物的智力：因?yàn)槲覀儠?huì)說(shuō)話、會(huì)寫字、做很多了不起的事情……所以我們把所有做不到我們能做的事的動(dòng)物都?xì)w類為不太聰明的物種。但是，在海豚的世界里，我們會(huì)表現(xiàn)得相當(dāng)愚蠢：我們無(wú)法在水下聽到聲音，無(wú)法把自己的腦袋變成聲吶發(fā)生器，也無(wú)法發(fā)出像海豚那樣多種多樣的聲音。但即便如此，我們就不“聰明”了嗎？不，我們和海豚只是不一樣罷了。那么，海豚必須要“像人類一樣”才能被人類視作平等的生物來(lái)對(duì)待嗎？我們是否需要其他動(dòng)物做到“像我們一樣”，才能給予它們平等的待遇？

問題在于，人類不可能完全平等地對(duì)待任何與他們不同的生物。

Growing up with pets around my house, I’ve found my fondness towards animals early in my life. I would tend to these lovely creatures with love and care that has naturally led myself to aspire after becoming a veterinarian in my future life. Yet, hoping me to get a “decent” degree in subjects like law, my parents were initially opposed to this idea. It was for my persistence that mom and dad finally let me have my way, and it was the same persistence that, when I was studying veterinarian, persuaded my professor to allow me on a travel to Canary Islands, where the sea presented profusion of intimacy with dolphins, my newly found passion.

Spending lots of time there studying animal behaviour and taking care of them, I knew that I wanted more than this. My ambition was to understand how animals communicate with each other. When I was only five, I have already had my first experience in animal communication. By mimicking the sound of the mother cat, I successfully coaxed the kittens out of their hiding place and played with them. With the help of a German professor, I moved to Israel to continue my study on dolphins. How they interact among themselves and with human beings? What methods they deploy to communicate? How do they convey their need?

All this time, I haven’t forgot the other seeking of mine: helping animals. I have been to facilities and institutes in the U.S. and Canada, working with staff there to offer medical treatment and protection mainly to marine animals.

After this, in 2007, I came to China, where my post-doctoral research awaited. I have collaborated with several institutes. Since 2017, I have been working here at Jianghan University.

The Wonders of Dolphins and Sounds

Dolphins and humans are both social mammals. In fact, these two types of mammals share a very similar social structure, namely the fission-fusion society. What does this mean? A fission-fusion society is where individuals are grouped into small families. Each individual in one family will have many agendas to attend on a routine basis—for example, humans have to go to work, and dolphins have to go out and hunt—each of us will leave for our separate business, but we all come back togetheragain at the end of the day. Yet, dolphins and humans are no doubt different. We live in different environments, thus we developed different sensory systems to adapt to and master these environments. We, living on firm lands, have our unique brain composition that are different to the brains of dolphins. Yet despite this difference, humans and dolphins share the need to communicate within their little or big societies.

Living and communicating undersea like dolphins may face quite a few challenges. One of the challenges is visual sight, for that a deep water environment can be dark and dense, the place where little light can reach. Even when the water is very clear, visible light can only travel 100 metres beneath the sea level. Actually, the sea water is hardly that clear, not to mention the disruption of waves and obstruction coming from seaweed and other things in the water. So it is far more likely that we can only see things metres, even centimetres away. In this, visual senses are not that useful for marine animals. But how can dolphins swim around, make friends with other dolphins, or hide away from predators with such poor eyesight? What senses are they going to utilize? The answer is sound!

The speed at which the sound travels in sea water is under multiple affecting factors. Because of the difference in density of water and air, sound can travel 4.5 times faster below the sea level than it does above. The transmission speed of sound also has to do with temperature and salinity. The warmer and saltier the water is, the faster the sound travels. More to this, in deeper areas of the ocean, where the water pressure is significantly higher than the surface, sound will accordingly travels at a faster speed .

We can certainly hear sounds in the water, too. But are dolphins hearing the same as we do? Unfortunately, we can only receive a limited range of frequencies of sound in the water owing to the shapes and structures of our human ears. It is for the same reason that we are not able to discern what direction the sound is coming from when swimming. How about dolphins? They are lot more advanced in regard of hearing under the water, unlike human, who can only receive frequencies in the range between 20 Hz to 15 kHz, while dolphins can pick up sound frequencies all the way from 75 Hz to 150 kHz.

How do dolphins make sounds? We human beings use our vocal cords to produce sounds, whereas dolphins have taken up a different method—they make sounds through the nasal organs, which are located in the melon (the round part on top of their head). Air will enter through blowholes into a pocketshaped structures which will vibrate, thus producing sounds. But the core of dolphin’s sound-making are their two sets of liplike organs. This dual-set of lips has allowed them to produce two types of sounds at the same time: whistles to communicate among individuals and echolocation to scan the environment.

Making sounds is just half of the equation. Now, how do dolphins hear these sounds? The fat tissue in the innerest part of the melon, it is of the same density of water. This tissue functions like a lens and can change its shape, transmitting the sound out in different directions. Around the jaws of a dolphin exists similar fat tissues. When the sound comes, fat tissues inside the jaw bones will perceive them, later transmit them to inner parts of dolphin ears that are also surrounded by the same fat tissues. Though they have ears, and also ear canals, but due to different structures from those of a human being, dolphins cannot hear as well out of water as they do under.

Dolphins’ Different Sounds

To understand sounds made by dolphins, researchers have separated out several patterns of sonograms. From these different patterns of sounds, scientists are able to identify the context where these sounds were made, what kind of emotions the dolphins are experiencing, or whether the dolphins are moving or are engaged in other things.

Now we will discuss different types of sounds a dolphin can make. First, there are sounds called “whistles”, of which the average frequency range can be between 75 Hz to 24 kHz (with some whistles going above 24 kHz). Whistles are omnidirectional which means it is difficult to identify which dolphin produces them. Whistles are composed by two parts: the fundamental frequency which is the main whistle, and the harmonics which occur at integer multiples of the fundamental frequency and usually extend into the ultrasonic (>20 kHz) range. Whistles that contain both non-directional and directional components are called “mixed directionality” sounds. In fact, researchers found out that the harmonics could be used for direction-tracking. So when a dolphin is both conveying his or her message and position, he or she will release both whistle sounds and harmonics. People have names, and we know each other by names. Dolphins have names, too - signature whistles. Each individual dolphin can label him or herself with a specific whistle tone - like a name - that is specific to each individual. The signature whistle can be also imitated by other dolphins to call upon the specific individual, just like we call the name of a person.

Besides whistling, dolphins have another type of sounds called echolocation clicks, which sounds like wooden sticks hitting each other. The dolphins use this type of sounds to scan their surroundings and look for food or obstacles. Each click sound is followed by an interval, in which dolphins are waiting for the echo of the click to come back and then to produce another click. Calculating this time lapse, dolphins can figure out how close they are to a certain object, thus mapping out the environment.

There is another type of sound called “burst pulse sound” which contains emotional components. This type of sounds are used by dolphins when they feel upset or argue with each others. Scientists would also describe this type of sounds with different names depending on how the sound goes: yelp, cry, weep. Different kinds of dolphins produce different kinds of sounds. For example, the finless porpoise, can only make pulse sounds but not whistles.

Dolphins’ Perceptual World

Human beings mainly create their reality through visions and speeches. We see something new, we name it, therefore recognize it. In general, the concept of “self” is based on information processed by the brain such as external information about reference axis of space and time with the self at the centre, and internal information about the position and orientation of the head and the body. These are elements of construction of the self. Memories, expectations, plans and so on are just additional elements. For dolphins, all the information about the external world come with the echolocation.

While human would say, “do you see what I see” or “do you see what I am telling you?” (if the person is talking about something), dolphins put it in another way, “do you see what I hear”. Every time a dolphin produces echolocation clicks to scan the surrounding environment, the echoes of the clicks will come back to the source, giving a sort of “holographic image” of what has been scanned. Here comes the amazing part: these echoes can be picked up by another dolphin in the vicinity who will receive the exact same type of “holographic image”. When different humans see the same object, they will perceive it differently, that depends on how each of them perceive their reality. Echolocation shares an unusual structural feature with human language, namely, the construction of the reality by the brain, is based on a signal generated by an individual. In the construction of a reality from echolocation, dolphins could share “raw” sensory information with one another, which would be even more unusual than the way we share information with language. Since the information are in the auditory domain, the “objects” that they generate would be as real as human seenobjects rather than heard-objects, that are so difficult for us to imagine. Even though it is just a speculation, the possibility of a social or communal cognition is something can be seriously considered. In fact, a perceptual world constructed from shared raw data would permit unusual group cohesion and a different kind of individuation. The dolphins’ social world could be an active rather than purely passive communal world. It would be as if humans were able to share the exact same image perceived by one individual. Therefore, the concept of an “individual” would be redefined where a communal experience might change the boundaries of the self to include several individuals.

This hypothesis could be supported by the special structure of the dolphins’ brain. The human brain can be differentiated into three main complexes: the reptilian complex, the limbic system and the cortex. However, with cetaceans we see a radical evolutionary jump with the inclusion of a fourth segment. This segment, called the paralimbic, features between the limbic and cortex, and it erupts into the cortex. This structure is present only in cetaceans and not in any other animal on earth. This unique evolution of the cetacean’s entire limbic system, which is a combination of multiple structures in the brain that deal with emotions and the formation of memories, suggests that cetaceans have the ability to process more complex thoughts and emotions. Since the system is so large in cetaceans, and the unique paralimbic lobe merges with the cortex, it is believed that the lobe may create a mixture of both emotional and cognitive thinking. The paralimbic lobe is also believed to be a continuation of the sensory and motor areas. For humans, projection areas are widely separated from one another, meaning anything we perceive from sight, sound and impulses must travel along fibre tracts with a great loss of time and information. The cetacean’s paralimbic lobe brings this all together in one, processing information rapidly with a richness that we cannot understand. The unique evolution of the paralimbic system suggests that the animals are doing something very sophisticated or complex while they’re processing together, emotions and sounds, and their brains may have adapted for a type of social connectivity unprecedented in the animals kingdom, taking the concept of social to a different level. Dolphins have a very strong cohesiveness in term of grouping: in fact, when one or two animals are sick and stranded, all the rest of the herd follows. A lot of this comes down to the “emotional attachment”, with a possible strong sense in these animals that if something happen to an individual, it happens to the entire group. Some scientist identify this type of cohesion among dolphins as a “collective soul”.

So do we need dolphins to be “l(fā)ike us” to be considered intelligent? Cetaceans have the biggest of the brain among animals, including humans, but this does not make them more intelligent than us. Defining intelligence is a tricky issue, and till now we did not yet completely understand the functions of human brain and found out the structure that defines intelligence. We, usually, define intelligence in other animals with the construction of our reality: we talk, we write, we do amazing things...and we classify animal species as less intelligent because they are not able to do things we do. But in a dolphin world we would be pretty stupid beings: we are not able to hear sounds underwater, to produce sonar with our heads, and to make the sounds as dolphins do. Are we less intelligent because of that? No. We are just different. So, do we need dolphins to be “l(fā)ike humans” to be treated as equal? Do we need other animals to be “l(fā)ike us” to have them treated as equal?

The problem lies in the fact that humans are mostly unable to treat as equal any being different from them. (

Yang Yunzhou contributed to this article

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