Cognition: do we all think in the same way? 

With the link between (inter­nal) lan­guage, thought, and self-aware­ness being estab­lished, the ques­tion aris­es as to whether depri­va­tion of this abil­i­ty affects cog­ni­tive and metacog­ni­tive func­tions. In some cas­es of non-flu­ent apha­sia, par­tial or com­plete loss of the abil­i­ty to speak aloud because of brain lesion, inter­nal speech is also affect­ed. In these cas­es, cog­ni­tive and mem­o­ry prob­lems are often also observed. How­ev­er, these dis­or­ders are not nec­es­sar­i­ly due to the deficit in inner speech, as the brain lesion itself can affect sev­er­al cog­ni­tive processes. 

A piece of the puz­zle can be found in stud­ies of indi­vid­u­als who start­ed talk­ing late in child­hood, the famous “late-talk­ers”. A famous case is that of Albert Ein­stein, who is said to have had a lan­guage delay in child­hood. In these indi­vid­u­als, can con­cepts still emerge and be manip­u­lat­ed men­tal­ly, with a poor­ly devel­oped sense of language? 

The math­e­mati­cian Jacques Hadamard record­ed Einstein’s tes­ti­mo­ny on his cog­ni­tive func­tion­ing¹. When asked about the men­tal images or forms of “inner words” he employed in think­ing, Albert Ein­stein replied, “the words or the lan­guage, as they are writ­ten or spo­ken, do not seem to play any role in my mech­a­nism of thought. The psy­chi­cal enti­ties which seem to serve as ele­ments in thought are cer­tain signs and more or less clear images which can be ‘vol­un­tar­i­ly’ repro­duced and combined.” 

Thus, Einstein’s use of lan­guage only came at a sec­ond stage, in which he had to “trans­late” his thoughts into words for oth­ers. It is not clear whether this non-ver­bal mode of think­ing is causal­ly relat­ed to his late onset of speech, but it does reveal that a form of con­cep­tu­al think­ing can take place with­out lan­guage. It is even pos­si­ble to con­sid­er that think­ing can some­times take place in some indi­vid­u­als not only with­out lan­guage but also with­out visu­al images and phys­i­cal sen­sa­tion. Indeed, recent research in cog­ni­tive sci­ence reveals that men­tal rep­re­sen­ta­tions are some­times amodal, or abstract.

Think­ing can some­times take place not only with­out lan­guage but also with­out visu­al images and phys­i­cal sensation.

The nature of men­tal rep­re­sen­ta­tions has long been the sub­ject of debate, between pro­po­nents of embod­ied, or somatosen­so­ry, cog­ni­tion and defend­ers of the abstract men­tal­ist con­cep­tion. These debates have been rekin­dled recent­ly by the obser­va­tion of atyp­i­cal forms of men­tal imagery. 

In 2010, the neu­rol­o­gist Adam Zeman and his team report­ed the case of a patient who lost the abil­i­ty to vol­un­tar­i­ly visu­alise after an angio­plas­ty². His men­tal visu­al­i­sa­tion deficit was not accom­pa­nied by any visu­al recog­ni­tion or oth­er impair­ment. For exam­ple, he was able to describe his city per­fect­ly, but was unable to pic­ture it in his mind.  Zeman’s arti­cle received a lot of media atten­tion and many peo­ple spon­ta­neous­ly report­ed that they were born with­out visu­al imagery. Sur­veys then revealed that a sig­nif­i­cant pro­por­tion of the gen­er­al pop­u­la­tion appears to lack vol­un­tary visu­al men­tal imagery innately. 

In 2015, Zeman and his team there­fore intro­duced the term ‘aphan­ta­sia’, from the Greek φαντασία (“imag­i­na­tion”), to describe this spe­cif­ic lack of men­tal imagery³. It has also emerged that the inabil­i­ty to vol­un­tar­i­ly cre­ate men­tal images can extend to oth­er sens­es: sounds, smells, tastes, touch. There is still no objec­tive test to know whether one has aphan­ta­sia or not, but some recent exper­i­ments seem promis­ing. For exam­ple, researchers have shown that prim­ing bias­es in men­tal imagery that are usu­al­ly observed when pre­sent­ed with ambigu­ous visu­al stim­uli are absent in peo­ple who self-report aphan­ta­sia. Fur­ther­more, neu­roimag­ing stud­ies have revealed pat­terns of neur­al acti­va­tion mod­u­lat­ed by the strength of indi­vid­ual visu­al imagery. Tak­en togeth­er, these results sug­gest that aphan­ta­sia may be a gen­uine absence of sen­so­ry cor­re­lates dur­ing men­tal representation.

At the Lab­o­ra­toire de Psy­cholo­gie et Neu­roCog­ni­tion in Greno­ble, we launched a large online study on this top­ic in July 2021. The study is still in progress and can be con­duct­ed in Eng­lish or French⁴⁵. It includes ques­tion­naires on men­tal rep­re­sen­ta­tions and imagery and an audio per­cep­tu­al test. We have recruit­ed our par­tic­i­pants very broad­ly and by tar­get­ing the net­works of peo­ple con­cerned with aphan­ta­sia. To date, out of approx­i­mate­ly 1,000 par­tic­i­pants, we have already iden­ti­fied 200 peo­ple whose respons­es to the ques­tion­naires sug­gest aphan­ta­sia. Some of these peo­ple report that they can speak to them­selves inter­nal­ly, but that their inner lan­guage is not aur­al: it is just words, no voice sen­sa­tion, no into­na­tion, no visu­al image of writ­ten words or ges­tures (of sign lan­guage). In con­trast, our sur­vey revealed that some peo­ple have audi­to­ry ver­bal hyper­phan­ta­sia, i.e. an abil­i­ty to gen­er­ate very loud, vivid and clear­ly sen­so­ry inner ver­bal­i­sa­tions⁶.

Inner speech with­out audi­to­ry or visu­al sen­sa­tion, audi­to­ry and visu­al ver­bal aphan­ta­sia, rep­re­sents a chal­lenge to cur­rent the­o­ries of cog­ni­tion and lan­guage. Can we access words with­out their sound, their spelling, or their sign? Research in psy­cholin­guis­tics sug­gests that there is a lev­el of rep­re­sen­ta­tion, the lem­ma, in which we have access to cer­tain char­ac­ter­is­tics of the word, with­out hav­ing the phono­log­i­cal form, the sound, in mind. This is the “tip-of-the tongue” phe­nom­e­non. When speak­ing, we can some­times remem­ber cer­tain details of the word we are look­ing for, like the num­ber of syl­la­bles, the con­so­nant with which it begins, with­out being able to say it to our­selves in its whole form and there­fore to men­tal­ly sim­u­late its sound. 

At the oth­er extreme, hyper­phan­ta­sia, the abil­i­ty to hear voic­es in one’s head as clear­ly as in real­i­ty, rais­es the ques­tion of the lim­it between men­tal imagery and hal­lu­ci­na­tion. How can we avoid con­fus­ing the imag­ined voice with a voice actu­al­ly perceived?

Some stud­ies seem to pos­tu­late that aphan­ta­sia is a dis­or­der, but recent research sug­gests rather that it is sim­ply a spe­cif­ic mode of oper­a­tion, an atyp­i­cal men­tal func­tion­ing.  So, the ques­tion remains unre­solved. As does the ques­tion of whether hyper­phan­ta­sia is an advan­tage or a dis­ad­van­tage, espe­cial­ly when flash­backs or imag­ined sen­sa­tions become too intense. There is still lit­tle research on the con­se­quences of atyp­i­cal forms of men­tal imagery. It can be assumed that peo­ple with aphan­ta­sia process infor­ma­tion in a more seman­tic, fac­tu­al, or descrip­tive way, where­as peo­ple with hyper­phan­ta­sia would engage in more detailed sen­so­ry pro­cess­ing. The prac­tice of inner lan­guage in these two atyp­i­cal pop­u­la­tions prob­a­bly gives rise to very dif­fer­ent rep­re­sen­ta­tions of the self and it can be hypoth­e­sised that self-aware­ness is itself con­struct­ed in an extreme­ly var­ied man­ner. It is there­fore impor­tant to con­tin­ue to explore the diver­si­ty of forms of inner lan­guage and to sur­vey as many indi­vid­u­als as possible. 

Take part in our online sur­vey and fur­ther the research!

Interview by Pablo Andres