12月8号,发布在Neuropsychologia杂志上的一项报告"Does acquisition of Greeble expertise in prosopagnosia rule out a domain-general deficit"表明,脸盲症人不能识别出人面部的三维轮廓。
现实生活中有时我们会戏称自己有脸盲症,记不住谁是谁。实际上确实有病人一生都无法认清人的脸,或者在车祸后丧失了识别他人面孔的能力。
脸盲实验中所用的称为Greeble的立体物体
一位脑部受损的病人认不出人的面孔,这引发了关于人们怎么去识别复杂物体的科学讨论。
美国里士满大学的心理学家辛迪.布卡(Cindy Bukach)的调查报告中提出,一名脑部受损的病人没法记住脸的模样,是一种无法感知物体特征的一般征兆。患有脸盲症的病人不单单只是没法识别人脸,即使在强化训练后,他也识别不出电脑生成的三维立体物体。
布卡和她的同事们对患有脸盲症的病人LR进行了研究,LR在一场车祸后,右太阳穴下方的脑部受损,在这之后他连自己的女儿都没法认出来,但是却记得一些其他人显著的面部特征,比如某人的络腮胡子。
布卡说,其实有很多方法可以干扰到人识别脸部,但是根据我们现有证据表明,LR这种类型的脸盲症,影响到了他识别由多部分构成的复杂物体,脸部就是其中最常见的例子。眼睛,鼻子和嘴巴,它们的相对位置以及形状,这些都有助于把脸部作为一个单一整体来辨别。
在2006年的报告里,布卡的团队设计出了这样的实验,用两组眼睛、鼻子和嘴巴分别排列组合出8个不同脸部,让LR进行辨别。在短暂的观察后,LR在四分之一的时间里能成功的从这8种脸部中挑出正确的那个,如果他是根据某个单一面部特征来识别的话,那么大概就应该是这个概率。在后续实验里,布卡发现LR正是通过记住嘴部的特征来辨别脸部的。
在这项新的研究中,研究人员如法炮制出了8种称为Greeble的多维立体物体,同样是由三组部件,每组含两种不同的分部件分别排列组合而成,再让LR进行辨别。结果表明,LR只能在31%的时间里正确辨别,在几次强化训练后,情况仍然不能有所改善。 而让四个健康的人进行同样的辨别实验,一开始会有点困难,但经过强化训练后能辨别出大多数立体物体。
美国达特茅斯学院的心理学家布拉德利.杜查(Bradley Duchaine)之前曾报告过一个名字叫爱德华(Edward)的脸盲症病人,他一生都无法认清人的脸,但是通过学习却可以做到辨别Greeble这种立体物体。杜查认为,如果辨别脸部要依赖于学习辨别多个部件构成的物体,正常的实验者应该一开始,就和脸盲症患者一样,只能识别出很少的Greeble物体,但是经过训练过会比脸盲症患者表现好很多。杜查承认,LR的表现让人感到费解,这个研究的结果并不利于我们理解辨别脸部的机制。
关于这个问题布卡是这么回应的,不管是训练前还是训练后,LR识别物体的准确率都如此低的原因是,他每次都只着重看其中一个部件,当然不能很好的辨别整体。(生物谷Bioon.com)
doi:10.1016/j.neuropsychologia.2011.11.023
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Does acquisition of Greeble expertise in prosopagnosia rule out a domain-general deficit?
Bukach CM, Gauthier I, Tarr MJ, Kadlec H, Barth S, Ryan E, Turpin J, Bub DN.
According to the expertise account of face specialization, a deficit that affects general expertise mechanisms should similarly impair the expert individuation of both faces and other visually homogeneous object classes. To test this possibility, we attempted to train a prosopagnosic patient, LR, to become a Greeble expert using the standard Greeble expertise-training paradigm (Gauthier & Tarr, 2002). Previous research demonstrated that LR's prosopagnosia was related to an inability to simultaneously use multiple features in a speeded face recognition task (Bukach, Bub, Gauthier, & Tarr, 2006). We hypothesized that LR's inability to use multiple face features would manifest in his acquisition of Greeble expertise, even though his basic object recognition is unimpaired according to standard neuropsychological testing. Although LR was eventually able to reach expertise criterion, he took many more training sessions than controls, suggesting use of an abnormal strategy. To further explore LR's Greeble processing strategies, we assessed his ability to use multiple Greeble features both before and after Greeble training. LR's performance in two versions of this task demonstrates that, even after training, he relies heavily on a single feature to identify Greebles. This correspondence between LR's face recognition and post-training Greeble recognition supports the idea that impaired face recognition is simply the most visible symptom of a more general object recognition impairment in acquired prosopagnosia.