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Top1. Introduction
With the advances in medical technology, the average life expectancy of world population is increasing. Since the probability of becoming cognitively impaired increases with age (roughly 10% of over 65 years old people), one side effect of increasing life expectancy is the emerging number of dementia patients. It is said that currently there are already around 40 million dementia patients all over the world. The situation is particularly severe in developed countries where the problem of aging population proceeds. Japan, probably is the country in the most severe situation over the world. According to a recent statistical data report, the number of dementia patients in Japan has already exceeded two million (1.6% of the population), and the percentage will keep increasing to 4.45 million (4.1% of the population) by 2035 (Ministry of Health, Labour and Welfare, 2008).
On the other hand, another social phenomena associated with the transition to modern society is the growing occurrence of “lonely death,” i.e. people who live alone and died alone without being noticed. This is due to the increasing number of nuclear families and decreasing marriage rate of modern society. Particularly for elderly people who go out less frequently than young people, the lack of social relationship and the stress of being feeling lonely is considered to accelerate the progress of dementia. The connection with the separately living younger family of the children of elderly people (if available) is getting its importance.
Due to the fact that there is no really effective treatment of dementia available, the only way to relieve the situation is to assist the daily life of dementia patients or to prevent the progression of its symptoms. Reminiscence or life review (Butler, 1974) is a well-known method to slow the progress of the most prominent symptom of dementia and memory impairment. It is also reported in the literature (Lazarov et al. 2005; Kempermann, Gast, & Gage, 2002) that repetitive stimuli on cognitive functions in the environment are also effective in suppressing the degradation of specific cognitive abilities.
Pollak (Pollack, 2005) summarized current research trend of three assistive functions for elderly people with cognitive impairment:
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Ensuring that the elder is safe and that he/she performs the necessary daily activities, and, if not, alerting a caregiver
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Helping the elder to compensate for his/her impairment by assisting in the performance of daily activities
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Assessing the elder’s cognitive status
In particular, we believe that a conversational humanoid can perform the third function stated above. Conversation is a very high-level cognitive activity and involves large brain areas, language understanding, language production, and so on. It is believed that keeping engaging in conversation can activate brain activities, i.e. can mitigate the progress of cognitive impairment. The assessment should be natural, and it should not be unduly stressful for elderly people. If the agent system (Wang, 2009) can assess the patient’s cognitive status through conversations, that will be a more natural way of measuring the cognitive status of the patients. Moreover, interpersonal communication is one of the most preferable daily activities for elderly people.