The Apologist and the Revolutionary

Ra­tion­al­ists com­plain that most peo­ple are too will­ing to make ex­cuses for their po­si­tions, and too un­will­ing to aban­don those po­si­tions for ones that bet­ter fit the ev­i­dence. And most peo­ple re­ally are pretty bad at this. But cer­tain stroke vic­tims called anosog­nosi­acs are much, much worse.

Anosog­nosia is the con­di­tion of not be­ing aware of your own dis­abil­ities. To be clear, we’re not talk­ing minor dis­abil­ities here, the sort that only show up dur­ing a com­pre­hen­sive clini­cal exam. We’re talk­ing paral­y­sis or even blind­ness1. Things that should be pretty hard to miss.

Take the ex­am­ple of the woman dis­cussed in Lish­man’s Or­ganic Psy­chi­a­try. After a right-hemi­sphere stroke, she lost move­ment in her left arm but con­tin­u­ously de­nied it. When the doc­tor asked her to move her arm, and she ob­served it not mov­ing, she claimed that it wasn’t ac­tu­ally her arm, it was her daugh­ter’s. Why was her daugh­ter’s arm at­tached to her shoulder? The pa­tient claimed her daugh­ter had been there in the bed with her all week. Why was her wed­ding ring on her daugh­ter’s hand? The pa­tient said her daugh­ter had bor­rowed it. Where was the pa­tient’s arm? The pa­tient “turned her head and searched in a be­mused way over her left shoulder”.

Why won’t these pa­tients ad­mit they’re par­a­lyzed, and what are the im­pli­ca­tions for neu­rotyp­i­cal hu­mans? Dr. Vilaya­nur Ra­machan­dran, lead­ing neu­ro­scien­tist and cur­rent holder of the world land-speed record for hy­poth­e­sis gen­er­a­tion, has a the­ory.

One im­me­di­ately plau­si­ble hy­poth­e­sis: the pa­tient is un­able to cope psy­cholog­i­cally with the pos­si­bil­ity of be­ing par­a­lyzed, so he re­sponds with de­nial. Plau­si­ble, but ac­cord­ing to Dr. Ra­machan­dran, wrong. He notes that pa­tients with left-side strokes al­most never suffer anosog­nosia, even though the left side con­trols the right half of the body in about the same way the right side con­trols the left half. There must be some­thing spe­cial about the right hemi­sphere.

Another plau­si­ble hy­poth­e­sis: the part of the brain re­spon­si­ble for think­ing about the af­fected area was dam­aged in the stroke. There­fore, the pa­tient has lost ac­cess to the area, so to speak. Dr. Ra­machan­dran doesn’t like this idea ei­ther. The lack of right-sided anosog­nosia in left-hemi­sphere stroke vic­tims ar­gues against it as well. But how can we dis­con­firm it?

Dr. Ra­machan­dran performed an ex­per­i­ment2 where he “par­a­lyzed” an anosog­nosiac’s good right arm. He placed it in a clever sys­tem of mir­rors that caused a re­search as­sis­tant’s arm to look as if it was at­tached to the pa­tient’s shoulder. Ra­machan­dran told the pa­tient to move his own right arm, and the false arm didn’t move. What hap­pened? The pa­tient claimed he could see the arm mov­ing—a clas­sic anosog­nosiac re­sponse. This sug­gests that the anosog­nosia is not speci­fi­cally a deficit of the brain’s left-arm mon­i­tor­ing sys­tem, but rather some sort of failure of ra­tio­nal­ity.

Says Dr. Ra­machan­dran:

The rea­son anosog­nosia is so puz­zling is that we have come to re­gard the ‘in­tel­lect’ as pri­mar­ily propo­si­tional in char­ac­ter and one or­di­nar­ily ex­pects propo­si­tional logic to be in­ter­nally con­sis­tent. To listen to a pa­tient deny own­er­ship of her arm and yet, in the same breath, ad­mit that it is at­tached to her shoulder is one of the most per­plex­ing phe­nom­ena that one can en­counter as a neu­rol­o­gist.

So what’s Dr. Ra­machan­dran’s solu­tion? He posits two differ­ent rea­son­ing mod­ules lo­cated in the two differ­ent hemi­spheres. The left brain tries to fit the data to the the­ory to pre­serve a co­her­ent in­ter­nal nar­ra­tive and pre­vent a per­son from jump­ing back and forth be­tween con­clu­sions upon each new data point. It is pri­mar­ily an apol­o­gist, there to ex­plain why any ex­pe­rience is ex­actly what its own the­ory would have pre­dicted. The right brain is the seat of the sec­ond virtue. When it’s had enough of the left-brain’s con­fab­u­lat­ing, it ini­ti­ates a Kuh­nian paradigm shift to a com­pletely new nar­ra­tive. Ra­machan­dran de­scribes it as “a left-wing rev­olu­tion­ary”.

Nor­mally these two sys­tems work in bal­ance. But if a stroke takes the rev­olu­tion­ary offline, the brain loses its abil­ity to change its mind about any­thing sig­nifi­cant. If your left arm was work­ing be­fore your stroke, the lit­tle voice that ought to tell you it might be time to re­ject the “left arm works fine” the­ory goes silent. The only one left is the poor apol­o­gist, who must tire­lessly in­vent stranger and stranger ex­cuses for why all the facts re­ally fit the “left arm works fine” the­ory perfectly well.

It gets weirder. For some rea­son, squirt­ing cold wa­ter into the left ear canal wakes up the rev­olu­tion­ary. Maybe the in­tense sen­sory in­put from an un­ex­pected source makes the right hemi­sphere un­usu­ally aroused. Maybe dis­tor­ing the bal­ance sense causes the eyes to move rapidly, ac­ti­vat­ing a la­tent sys­tem for in­ter-hemi­sphere co-or­di­na­tion usu­ally re­stricted to REM sleep3. In any case, a pa­tient who has been deny­ing paral­y­sis for weeks or months will, upon hav­ing cold wa­ter placed in the ear, ad­mit to paral­y­sis, ad­mit to hav­ing been par­a­lyzed the past few weeks or months, and ex­press be­wil­der­ment at hav­ing ever de­nied such an ob­vi­ous fact. And then the effect wears off, and the pa­tient not only de­nies the paral­y­sis but de­nies ever hav­ing ad­mit­ted to it.

This di­vorce be­tween the apol­o­gist and the rev­olu­tion­ary might also ex­plain some of the odd be­hav­ior of split-brain pa­tients. Con­sider the fol­low­ing ex­per­i­ment: a split-brain pa­tient was shown two images, one in each vi­sual field. The left hemi­sphere re­ceived the image of a chicken claw, and the right hemi­sphere re­ceived the image of a snowed-in house. The pa­tient was asked ver­bally to de­scribe what he saw, ac­ti­vat­ing the left (more ver­bal) hemi­sphere. The pa­tient said he saw a chicken claw, as ex­pected. Then the pa­tient was asked to point with his left hand (con­trol­led by the right hemi­sphere) to a pic­ture re­lated to the scene. Among the pic­tures available were a shovel and a chicken. He pointed to the shovel. So far, no cra­zier than what we’ve come to ex­pect from neu­ro­science.

Now the doc­tor ver­bally asked the pa­tient to de­scribe why he just pointed to the shovel. The pa­tient ver­bally (left hemi­sphere!) an­swered that he saw a chicken claw, and of course shov­els are nec­es­sary to clean out chicken sheds, so he pointed to the shovel to in­di­cate chick­ens. The apol­o­gist in the left-brain is hel­pless to do any­thing be­sides ex­plain why the data fits its own the­ory, and its own the­ory is that what­ever hap­pened had some­thing to do with chick­ens, dammit!

The log­i­cal fol­low-up ex­per­i­ment would be to ask the right hemi­sphere to ex­plain the left hemi­sphere’s ac­tions. Un­for­tu­nately, the right hemi­sphere is ei­ther non-lin­guis­tic or as close as to make no differ­ence. What­ever its thoughts, it’s keep­ing them to it­self. know, my mouth is still agape at that whole cold-wa­ter-in-the-ear trick. I have this fan­tasy of gath­er­ing all the lead­ing cre­ation­ists to­gether and squirt­ing ice cold wa­ter in each of their left ears. All of a sud­den, one and all, they ad­mit their mis­takes, and ex­press baf­fle­ment at ever hav­ing be­lieved such non­sense. And then ten min­utes later the effect wears off, and they’re all back to talk­ing about ir­re­ducible com­plex­ity or what­ever. I don’t mind. I’ve already run off to up­load the video to YouTube.

This is surely so great an ex­ag­ger­a­tion of Dr. Ra­machan­dran’s the­ory as to be a par­ody of it. And in any case I don’t know how much to be­lieve all this about differ­ent rea­son­ing mod­ules, or how closely the in­tu­itive un­der­stand­ing of it I take from his pa­per matches the way a neu­ro­scien­tist would think of it. Are the apol­o­gist and the rev­olu­tion­ary ac­tive in nor­mal thought? Do anosog­nosi­acs demon­strate the same patholog­i­cal in­abil­ity to change their mind on is­sues other than their dis­abil­ities? What of the ar­gu­ment that con­fab­u­la­tion is a rather com­mon failure mode of the brain, shared by some con­di­tions that have lit­tle to do with right-hemi­sphere failure? Why does the effect of the cold wa­ter wear off so quickly? I’ve yet to see any re­ally satis­fy­ing an­swers to any of these ques­tions.

But whether Ra­machan­dran is right or wrong, I give him enor­mous credit for do­ing se­ri­ous re­search into the neu­ral cor­re­lates of hu­man ra­tio­nal­ity. I can think of few other fields that offer so many po­ten­tial benefits.


1: See An­ton-Babin­ski syndrome

2: See Ra­machan­dran’s “The Evolu­tion­ary Biol­ogy of Self-De­cep­tion”, the link from “posits two differ­ent rea­son­ing mod­ules” in this ar­ti­cle.

3: For Ra­machan­dran’s thoughts on REM, again see “The Evolu­tion­ary Biol­ogy of Self De­cep­tion”