From the public survey, we found that the only term that can be said to be popular among the general public in Japan is clinical study. Furthermore, the most gripping issue is that 80% or more of the respondents in the group of people 60s–70s indicated that they had never heard the following six terms: interventional study, prospective clinical study, cohort study, Phase 1 clinical trial, double-blind study, and placebo; and also the group of people under 60 had not heard the following six terms: interventional study, prospective clinical study, cohort study, Phase 1 clinical trial, double-blind study, and randomized clinical trial. Several of these terms have been studied in previous research in Japan. For instance, placebo has been studied by both Yoshida et al. (2013) and Tsutani et al. (2015); the results of awareness obtained by these researchers (former: approximately 14.9%; latter: approximately 30% [males 30.6%, females 27.1%]) and our results (the group of people under 60: 24.0%; the group of people 60s–70s: 14.7% [overall 20.8%]) indicate roughly equivalent levels of awareness. Yoshida et al. also polled respondents about the terms double-blind study and Phase 1 clinical trial; 7.3% and 8.6% of respondents were aware of these terms, respectively, consistent with our results. In comparison to these findings, we can surmise that the results of this study are valid.

In this way, the general public’s awareness of the above six terms is low. If the physicians engaged in the research can predict this accurately, they will be conscious of the need to provide sufficient explanations of medical research terminology to the general public. Unfortunately, however, the physicians’ survey revealed that physicians could not make correct predictions. In the physicians’ survey, physicians estimated that, compared to the group of people 60s–70s, a greater percentage of the group of people under 60 would be familiar with all surveyed medical research terms. However, most terms were more familiar to respondents in the group of people 60s–70s than those in the group of people under 60, indicating a gap between physician predictions and public awareness. This suggests the possibility that physicians are not providing the quality explanations that participants in the group of people under 60 require. We assume one reason for the generally higher awareness among respondents in the group of people 60s–70s is as follows. In 2019, the average life expectancy in Japan was 81.41 years for men (third highest in the world) and 87.45 years for women (second highest in the world), and in general, Japanese people are very conscious of health and medical care. In a survey of men and women aged 55 years and older conducted by the Japanese government, 90.7% reported that they habitually engaged in health behaviors. One of these activities included “gaining knowledge about health and medical care,” which was endorsed by more than one-third (36.5%) of the respondents (Cabinet Office, Government of Japan 2017). Perhaps their attention is partially drawn to medical research due to this mindset. Physicians must reanalyze their perceptions.

There were four terms for which physicians predicted public awareness to be significantly higher than actual awareness: placebo, cohort study, double-blind study (both age groups), and randomized clinical trial (the group of people under 60 only). These raise the possibility that the physician will not explain what participants need.

From these results, we found two factors that may hinder the proper IC in Japan: (1) many terms of medical research are not familiar to the general public, and (2) physicians generally fail to predict public awareness accurately. To remove these factors, it is considered that various measures should be taken, including the following.

First is “informing” the fact. It is critical to inform physicians about the general public’s low awareness of the six terms above and lesser familiarity (than assumed) with the following terms: placebo, cohort study, double-blind study, and randomized clinical trial. And also, informing those facts to research ethics committees (RECs) may be effective as they review informed consent forms. The second measure is “enhancing” the skill of physicians. Physicians should enhance their skills to explain medical research terminology to research subjects in an easy-to-understand manner. Many studies have been conducted to develop training programs to boost physicians’ communication skills for proper informed consent in medical research (Occa and Morgan 2018), and some of which have explored the explanation of the terms “randomization” and “placebo.” For example, Yap et al. recommended physicians for using metaphors like “flip of a coin,” “picking a number out of the hat,” “a roll of the dice,” and “luck of the draw” for “randomization” (Yap et al. 2009). However, as far as we know, no programs are focusing on the explanation of medical research terminology despite their need. Though the programs should be developed circumspectly, one idea would be to hold a workshop where physicians who are in charge of informed consent, the general public, and the patients (including ex-patients) who have experience participating in clinical research collaboratively discuss and create some samples of explanations text of terms. Through the workshop, it is expectable for physicians to learn whether the general public and patients can understand the explanations that are usually given, and what kind of information is needed for them. And then, the third measure is “sharing” the information. The created samples of explanatory text should be made public so that physicians and REC members can refer to them. In Japan, by relevant laws and guidelines, all persons involved in clinical research including physicians in charge of informed consent are obliged to undergo research ethics education programs before starting and during the research, and REC members are also required to take educational programs. In these circumstances, it is appropriate to incorporate those measures in such programs. Fortunately, we are conducting a project funded by a national research agency to produce video programs for researchers and REC members, respectively, and hold seminars on research ethics. We are willing to contribute to “informing” and “sharing” by producing video programs and “enhancing” by conducting seminars.

The last measure is “increasing” literacy. It is necessary to raise the general public’s awareness of medical research terminology and literacy of medical research. As mentioned above, six out of the eleven terms were unheard of by more than 80% of the general public. This means that most of the general public will come across these terms for the first time when they or their family members are ill and are briefed by a physician for a clinical study. Considering previous research, there are concerns that such a situation may cause two adverse effects on obtaining proper informed consent. One is that research subjects may feel fear of becoming “a guinea pig” (Behrendt et al. 2011; Quinn et al. 2007), similar to “a last chance for someone who has no hope” (Quinn et al. 2007) or a “death sentence” (Quinn et al. 2012). For instance, in a study by Naidoo et al. on patients that participated in a randomized clinical trial, when providing IC, respondents felt fear of becoming “guinea pigs,” intimidated and confused by specialized terminology, and disappointment, anger, and depression at the prospect of allocation into the control group of the study; in short, these processes were associated with psychological burdens (Naidoo et al. 2020). Further, unless a participant knows the facts, such as that many clinical studies are conducted for the development of medicine or that various methods such as randomized allocation are used in clinical studies to obtain reliable data, they may feel distrust toward their physicians. Another possible effect is that “therapeutic misconception” (Appelbaum et al. 1987; Henderson et al. 2006) is more likely to occur. In this way, even if the requirement (i), namely information, for proper IC is met, it may be difficult for the participant to fully understand the explanation and make a decision on participation in situations where they are proposed to participate in the medical research. In these circumstances, it is crucial to raise the general public’s literacy of medical research, including medical research terms. To consider the way to raise literacy, it is necessary to investigate why the Japanese public is unfamiliar with medical research terminology. In this regard, Japan ranks high in scientific literacy, having performed second-best out of 37 countries on the 2018 Program for International Student Assessment (PISA), a test conducted by the Organization of Economic Cooperation and Development (OECD) to evaluate learning attainment among 15-year-olds (OECD 2019). We speculate a major cause for this low familiarity with medical research terminology, despite high scientific literacy, is a lack of education. Japanese students are not taught the basic knowledge related to medical research in secondary education. For this, the national government should consider implementing education related to basic knowledge of medical research. Along with that, taking measures to raise public literacy should be taken immediately. For us, we will produce educational tools such as videos or leaflets using the explanation texts of the terms made in the second measure above so that young people can easily learn about medical research.

It is difficult to establish whether the medical research terminology remains largely unfamiliar to the general public in other countries, as a similar survey has not been conducted before. However, concerning the term randomized clinical trial, a survey carried out in the UK that targeted the general public found that only 28.6% of respondents had heard of the term (Mackenzie et al. 2010); this is similar to our result among Japanese people. Further, a 2020 public survey conducted by the American National Cancer Institute found that 36.4% of respondents indicated “I don’t know anything about clinical trials,” whereas 49.9% indicated “I know a little bit about clinical trials” (National Cancer Institute 2020). These findings suggest that even in countries where the clinical research is quite common and advanced, the general public’s awareness of clinical research is probably not high. Therefore, the measures above are worth considering not only in Japan but also in countries where the general public’s literacy in medical research is not high.

Our study has some limitations. First, our subjects were individuals registered with an online survey company. According to a 2018 investigation conducted by the Japanese government, the country’s Internet usage rate exceeded 90% in every adult age group between the 20s and 50s but declined in older demographics (60–64 years: 81.2%, 65–69 years: 67.9%, 70–79: 46.7%, ≥ 80: 20.1%) (Ministry of Internal Affairs and Communication 2018). For this reason, Japanese adults over 60 years of age who register with online survey companies have superior access to information than their peers in the same generation. Previous studies in the USA have shown that those registered with online survey companies have a relatively high educational background (Chang and Krosnick 2009). Though we could not analyze this factor since we did not collect information regarding the respondents’ educational backgrounds, there may be a similar tendency in Japan. In addition, it should also be noted that the response rate of the general public survey was as low as 12.8%. Online survey company registrants were requested to respond to various surveys, so that those who responded to our survey might have already been relatively interested in medical research. And also, we defined the “general public” as those who were not likely to touch with medical research terminology for occupational reasons, then excluded the candidate who worked or had family members working in several professions. Thus, some bias may be present in our sampling methodology for the so-called general public. Further, some bias is also inherent in our physician sample, as only physicians registered with the online survey company were enrolled. Moreover, the number of respondents under the age of 40 was significantly smaller, and that of respondents in their 50s and above was significantly higher than the actual age distribution of Japanese physicians. Those limitations indicate vulnerabilities regarding the representativeness of the population of responses. Hence, in the future, it is necessary to verify and reinforce the findings obtained from these surveys, for example, through qualitative research.