Prosopagnosia and Its Relation with Face Specific Systems - Coursework Example

Prosopagnosia and its relation with face specific systems Prosopagnosia “Prosopagnosia, a loss in the ability to recognize faces, is easy to diagnose but difficult to explain” (Duchaine, 2000, p.79). Face recognition disabilities were reported even in nineteenth century; however it was not considered as a major disease till the beginning of the second half of the twentieth century. People with prosopagnosia may behave normally in all the other circumstances, except in circumstances in which they force to identify certain faces. They may recognize other objects quite normally, but when it comes to face recognition, they may struggle to identify the faces they observed in their past life. Since the exact reasons for prosopagnosia are still unknown, no therapies guarantee complete recovery from prosopagnosia. According to Oliver Sacks (a psychologist and a victim of prosopagnosia), “people with prosopagnosia need to be resourceful, inventive in finding strategies for circumventing their deficits: recognizing people by an unusual nose or beard, or by their spectacles, or a certain type of clothing” (Sacks, 2010). Face recognition is an important function of the brain and the importance of face recognition in human life cannot be underestimated. Consider a person who is living in this world without the ability to recognize his friends and relatives. A life with Prosopagnosia is horrible when we look into the consequences of this disease. Some people consider prosopagnosia as a normal disease whereas some others consider it as a psychological disorder. “Some investigators argue that it is caused by the impairment of a recognition system specialized for faces. Others argue in contrast that it is caused by an impairment of system of systems essential for face recognition, but not specialized for it” (Duchaine, 2000, p.79). It is a fact that in some cases people loss their face recognition ability after an accident which caused damages to the brain. On the other hand, there are many other cases in which people develop prosopagnosia gradually without a particular reason. That is why psychologists and medical experts are still searching the reasons for prosopagnosia in darkness. Recent researches have formulated many hypothesises and pointed out many reasons as the probable causes of Prosopagnosia. The existence of a face specific system is suggested by some of the researchers in this field. In their opinion, Prosopagnosia is caused by the problems occurred to the face recognition system rather than anything else. This paper analyses the above argument deeply with the help of some of the published studies. Prosopagnosia & face specific system “Much of the work on face perception has focused on front views of faces, but a face is a complex 3-D object that must be recognised from all directions” (Marotta et al, 2002, p.32). However, human ability to recognize faces from different angels is limited. It is easy for human to recognize a face when it is in a zero degree angle as shown in the figure below. Sample face from Max-Planck Face Database rotated in depth around the vertical axis. From left to right: full face (0°), right three-quarter (45°), and right profile (90°). (Marotta et al, 2002, p.37) In other words, full face will be visible to human eyes only when it is in zero degree angle. In all the other angles as shown in the figure above, some parts of the face will not be visible to a viewer. The ability of a normal human to recognize a face is more when it is viewed at zero angles than at any other angles. The above points will be helpful in further analysis of Prosopagnosia. The question; whether the human visual system consists of a standardized system for recognising objects or specific systems for identifying each objects, is a controversial and confusing one for psychologists and medical experts. This is because of the fact that people with Prosopagnosia disease show not many changes in recognising other objects even though they struggle to recognise faces. Farah et al (1995) conducted a comprehensive study to know whether people have same ability to recognise faces even when the faces were inverted. Their findings were given below. Does the human visual system contain a specialized system for face recognition, not used for the recognition of other objects? This question was addressed using the "face inversion effect" which refers to the loss of our normal proficiency at face perception when faces are inverted. Prosopagnosic subjects paradoxically performed better at matching inverted faces than upright faces, the opposite of the normal "face inversion effect". The fact that his impairment was most pronounced with the stimuli for which normal subjects show the greatest proficiency in face perception provides evidence of a neurologically localized module for upright face recognition in humans (Farah et al, 1995). The above findings reveal that Prosopagnosia patients have problems in identifying normal faces whereas they are able to recognize inverted faces. When the faces get inverted, Prosopagnosia patients started to identify those faces just as some other objects and were able to recognize it. However, when the faces become straight, they failed to recognize it. It should be noted that Prosopagnosia patients can recognize other objects irrespective of whether it is inverted or straight. For example, if a bottle is placed in straight and inverted positions alternatively, in front of the Prosopagnosia patients, they will be able to recognise it in both the cases. On the other hand, they may recognize an inverted face, but may struggle to recognise the upright faces. The above finding clearly shows the possibility of a specific element in our brain systems which recognize upright faces. Marotta et al (2002) also conducted similar studies in order to know more about the uncanny ways through which human brain recognises faces. They conducted their experiments on two prosopagnosic patients; (RN & CR) and their findings are listed below. The current study investigated the sensitivity of face recognition to two changes of the stimulus, a rotation in depth and an inversion, by comparing the performance of two prosopagnosic patients, RN and CR, with non-neurological control subjects on a face-matching task. The control subjects showed an effect of depth rotation, with errors and reaction times increasing systematically with rotation angle, and the traditional inversion effect, with errors and reaction times increasing under inverted conditions. In contrast, RN showed no effect of rotation or inversion on his error data but did show a less sensitively graded effect of rotation and the traditional inversion effect on reaction times. CR did not show a graded effect of rotation on his errors or reaction times. Although CR showed the traditional inversion effect on his error data, he displayed an inversion superiority effect on his reaction time data, which supports the claim that the damaged holistic processing systems continue to dominate face processing in prosopagnosia even though they are malfunctioning. These results suggest that the damage that occurs to the ventral temporal cortex in prosopagnosia may have forced the patients to rely on sources of information that are not dependent on the view of the face and, moreover, cannot be adapted to deal with rotated faces under both upright and inverted conditions (Marotta et al, 2002, p.31). The face inversion effects on Kilgour et al (2004) also yielded similar results as obtained by Marotta et al. They have pointed out that “some prosopagnosic individuals do not demonstrate the typical inversion effect, while others process inverted faces better than upright faces” (Kilgour et al 2004, p.707). In other words, it is not necessary that all the prosopagnosic individuals may respond to the face inversion testing in a similar fashion. In fact some of the prosopagnosic individuals may not show many differences while they respond to upright faces or inverted faces. The functioning of brain in recognising objects is still unknown to medical science. When the face recognition area of the brain undergoes damages, we will lose our ability to recognise people. When a face appears in front of the prosopagnosic patients, eyes will quickly transfer the signals from that face to the brain, from where these signals will be transferred to the face recognition area of the patient. Since the patient does not have the ability to process that information, the face may not be recognised. On the other hand, when an inverted face appear in front of the prosopagnosic patients, instead of sending signals to the face recognition area, brain will send those signals to the object recognition area. Since the object recognition area function well among prosopagnosic patients, they will recognize the inverted face more quickly. It should be noted that all the input signals from the senses are initially processed by the brain systems before sending these signals to particular areas of brain for more detailed analysis and synthesis. A considerable body of evidence from prosopagnosia seems to indicate that faces are processed by a more or less independent system. Prosopagnosia is a rare condition in which brain damage reduces a persons ability to recognize faces. Although the condition is almost always accompanied by other visual impairments, the deficit can be remarkably specific to faces. One possible explanation is that face recognition is in some way more difficult than other types of recognition, so mild damage to a general-purpose recognition system could affect face recognition more than nonface object recognition (Dailey et al, n. d, p.1) Naturally, face is the most active element on a human body. Unlike other parts of human body, face reveals many things about a person. That’s why; the nature or the creator incorporated a specific system for recognising faces. “Although perception of identity is important for social communication insofar as we interact differently with different people, perception of the changeable aspects of the face plays a far greater role in facilitating social communication” (Haxby et al, 2000, p.223). It is an accepted fact that more than 60% of the messages were communicated through nonverbal means in a direct face to face communication between two people. In other words, nonverbal communication means such as gestures, facial expressions, body languages etc are important in a direct communication process. Face is the most important organ which helps a person to communicate effectively using the nonverbal channels of communication. In other words, while communicating with others, a person may give more emphasize to the facial expressions of the opposite persons. Thus, while watching a person, facial aspects are stored more quickly in the minds of the viewer, than any other body aspects of that person. It is difficult for us to identify another person if his face is masked. Even if we are able to see all the other body parts of a person, it is difficult to recognize a person without facial identification. In short, the importance of face in identification process cannot be underestimated. From the above discussions, one thing is clear; some kind of face recognition system is prevailing among normal human beings. Now the question is whether these systems are inherited or developmental in nature. In other words, the question whether a person gets the inherited ability to recognize others or he should develop it as time goes on. According to Duchaine et al (2006), “face recognition involves developmental mechanisms different from those producing other visual recognition mechanisms”(Duchaine et al, 2006, p.1). They have conducted comprehensive studies in this topic and concluded the following things; “for each case that has been tested there have always been several untested alternative explanations that could account for the case. As such, each of these individuals has not been sufficiently tested to provide conclusive evidence for face-specific processes” (Duchaine et al, 2006, p.1). It is a fact that small children have less ability in recognising others compared to the adults. For example, it is difficult for a small child of the age of four or five to recognise a person after few years. On the other hand, it is easy for a normal adult to recognise people even after many years. In other words, face recognition ability is only in the beginning stages as far as the small children are concerned whereas for adult, such ability is already matured. As in the case of other developmental characteristics such as memory, emotions physical growth etc, face recognition ability also undergo exhaustion once a person started to enter his final phase of life. That is why extremely older generation often complain about their inability to recognize others. Many people often believe that such complaints are not caused by the problems in vision; however there are many old people with good eye sights, who make complaints about their inability to recognize others. It is evident that these people are facing face recognition problems rather than eye sight problems. Busygny et al (2010) have added another dimension to the concept of existence of face recognition systems in human mind. They have pointed out that prosopagnosic patients have problems in recognising objects in homogeneous categories. Their research findings are given below; We tested the prosopagnosic patient (PS) in three delayed forced-choice recognition experiments in which visual similarity between a target and its distractor was manipulated parametrically: novel 3D geometric shapes, morphed pictures of common objects, and morphed photographs of a highly homogenous familiar category (cars). In all experiments, PS showed normal performance and speed, and there was no evidence of a steeper increase of error rates. It seems that brain damage in adulthood may lead to selective recognition impairment for faces, perhaps the only category of visual stimuli for which holistic/configural perception is not only potentially at play, but is strictly necessary to individualize members of the category efficiently (Busygny et al, 2010, p.2051) The above findings rule out the possibility of acquired prosopagnosia. In other words, prosopagnosia is caused by some kind of malfunctioning of brain due to some specific reasons. If prosopagnosia is developmental, all the people irrespective of their intelligence, or health should develop prosopagnosia at some point of time in their lives. However, there were many people who recognized people without any problem even after the completion of 80 or 90 years of age. In short, it is difficult to conclude whether prosopagnosia is developmental or not. Harris et al (2005) have pointed out that “developmental prosopagnosia is defined by substandard behavioural performance in laboratory tests, not by clinical etiology” (Harris et al, 2005, p.2). In other words, prosopagnosia may appear among different people in different forms. It is not necessary that the prosopagnosia patients may demonstrate uniformity in their disease, even though all of them are affected by the same problem or disease. Conclusions Prosopagnosia is a mental disease which prevents a person from recognising the faces of others. It is possible for the prosopagnosic patients to identify other objects. Moreover it is possible for prosopagnosic patients to identify inverted faces more easily than upright faces. The above findings clearly point towards the existence of a specific face recognition system in human brain. Moreover, it is logical to believe that object recognition and face recognition systems in our brain are two distinctive entities. References 1. Busygny T, Graf M, Mayer E & Rossion B (2010). Acquired prosopagnosia as a face- specificdisorder: Ruling out the general visual similarity account. Neuropsychologia 48 (2010) 2051–2067. Retrieved from http://www.nefy.ucl.ac.be/facecatlab/PDF/BusignyG_Neuropsychol_2010.pdf 2. Dailey MN, Cottrell W G & Padgett C (n. d). A Mixture of Experts Model Exhibiting Prosopagnosia. 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