As countermeasure for preventing dementia of aging population, coimagination method has been developed. The coimagination method helps participants in utilizing brain cognitive functions of maintaining recent episodic memorization, retention and recall by the process of conversations. Hence, the risk of older adults in getting into mild cognitive impairment (MCI), which is a previous stage of dementia caused by disuse of brain cognitive functions, will decline. However, we observed situations of some older adults that recent episodic memory functions were not activated as expected. Such situations are older adults who talk about knowledge rather than episodic memories or older adults who talk about past experiences rather than recent experiences. Therefore, a novel coimagination program named coimagination method with expedition was developed to solve these situations. By adding expedition in a sightseeing area before the coimagination method, older adults have the opportunity to find topic of conversations through expedition. During conversation supported by the coimagination method, older adults are expected to recall their episodic memories in expedition and talk about it. The purpose of this research is to verify the effect of the coimagination method with expedition in older adults, by comparing mental time of older adults in the coimagination methods with and without expedition. Firstly, we estimate the mental time of older adults by analyzing their utterances during conversations supported by both coimagination methods. The past, present and future mental times of participants are enumerated in percentage. Secondly, we study the mental time travelling of participants during conversations. Finally, we study the transition points of mental time to find tendency of participants to talk about recent experiences. In this research, the analytical results validate the effectiveness of helping older adults to talk about recent episodic memories during conversation supported by the coimagination method with expedition compared to the coimagination method.

The increase of dementia patients is one of the problems caused by aged population not only in Japan but in many developed countries. As cognitive enhancement method for prevention of dementia, coimagination method is proposed: designed group conversation whose themes are selected from recent topics for training of recent episodic memory functions, since recent episodic memory functions decline before the onset of dementia. It is known that people who are disuse particular cognitive functions have higher risk of loosing the functions. However, the participants of the conversations supported by coimagination method sometimes refer to past topics rather than recent topics. The method is required for analyzing whether the topics deal with recent or past for effective intervention, which has not been established. Purpose of this study is to propose method for analyzing the temporal characteristics of the topics during conversation. Mental time travel, or chronesthesia, is the ability to be aware of one’s present, past or future which has been evolved in humans in particular. In order to estimate the mental time of the speaker from topics during conversation supported by coimagination method, we propose mental time estimation method by analyzing tenses and senses. We applied the method to the scripts of conversation supported by coimagination method. The result suggests that it’s possible to estimate mental time from analysis of the topics in conversation. The ratio of the reference of past, present and future of each speaker was enumerated. The individual differences of the tendencies were demonstrated as the ratios.