英文編修, 論文校對, 論文修改, 論文翻譯, 期刊發表, 摘要翻譯
意得輯觀點Editage Insights - Why you should not use the journal impact factor to evaluate research
首頁 » 作者資源 »意得輯觀點 -為何不該使用期刊影響因子評估研究

Dr. Eddy 將在此專欄與您分享他身為一名研究員多年來累積的【論文投稿發表】經驗。 請閱讀 Dr. Eddy 分享成功發表論文的技巧與國際期刊研究趨勢。


熱門話題
為何不該使用期刊影響因子評估研究

尤金•加菲爾德(Eugene Garfield )1最初提出期刊影響因子的目的是為資料庫挑選期刊,不幸的是,期刊影響因子(JIF)經常被他人錯誤使用,包括用來評估個別研究的影響力,甚至研究人員的威信。近期,此指標因為既有限制性和頻繁的誤用而遭受批評。2-4

一份期刊的影響因子指的是論文在特定時間內被引用的平均次數。5指標的計算和功能已於另一篇文章《期刊影響因子和其他衡量期刊影響力的標準》裡有詳細描述。在此,我們將更進一步探討有關影響因子的謬論,並指出使用它時需有的考量。6


期刊影響指數的正確用法
  • 衡量一份期刊的權威性
  • 比較某特定學術領域裡不同期刊的權威性
  • 幫助圖書館人員管理機構的期刊訂閱
  • 讓研究人員鑑定學科領域內該留意和適合投稿的期刊
  • 方便期刊比較預期和實際的引用次數,並和同一領域內的其它期刊相比
  • 使出版社進行市場調查
期刊影響指數的錯誤用法7
  • 評估單篇論文的影響力和個別研究人員的學術成就
  • 比較不同學術領域期刊
  • 贊助機構用它做為分配獎金依據
  • 作者把它作為篩選期刊的唯一考量
  • 招聘和升遷委員會把它定為預測一位研究人員未來成就的標準
  • 作者用此與其它同儕比較

期刊影響因子的特性

為了避免誤用,請參考和了解下列有關本指標的優、缺點。

期刊影響因子衡量的是一份期刊的品質,而並非單篇論文的品質

。指標的重點是期刊裡所有論文被引用的總累計次數,而不是單篇論文被引用的次數。根據知名的80/20法則,一份期刊裡20%優秀的論文會占總引用次數的80%,即使是《自然》等知名期刊也不例外。8一篇刊登於高影響因子期刊並不表示論文本身有影響力,論文可能根本還沒有被其他人引用,反之若一份期刊在某一年內有幾篇論文被高度引用,隨著時間將導致該期刊的影響因子出現異常的趨勢。9

期刊引文
期刊影響因子應該謹慎的用在衡量及比較個別期刊權威性,而非衡量單篇論文,更不是用來直接或間接評估任何研究人員或計畫的指標。

-歐洲科學編及學會10
僅衡量兩年內被引用的論文

當計算影響因子時,被納入衡量的是指某期刊兩年前至今論文被引用的次數。然而,不同學科領域有不同的引用方式。例如,健康科學論文於登入不久後就會被引用,而社會科學論文則通常是在兩年後才會被大量引用。11因此,於二年後被引用的論文常被忽略其真正的影響力。

無視引用的性質。

期刊裡的論文一旦被引用,不論褒貶,都將有助於其影響因子。即使論文被反駁或被舉為不良研究,仍然能增加期刊權威性。事實上,遭撤回的論文仍然能幫助期刊增加影響因子,因為若被其他論文引用,他們的撤回將不會對後者有任何效應。

僅排名來源數據庫收錄的期刊。

包含一萬兩千多種期刊的湯森路透Web of Science是用來計算影響因子的數位資料庫。雖然期刊數目不少且每年更新,但是不包含所有的期刊(尤其是不以英文出版的刊物)。沒有被Web of Science收錄的期刊將不會有任何影響因子,所以不能與被收錄的期刊相比。

您知道嗎
《天文物理期刊》一份特刊裡的13篇論文被引用的次數異常的高,導致期刊影響因子從2003年的6.247升至2004年的15.231。
影響因子會因期刊出版的文章類別而有所變動。

評論文章通常會整理及介紹先前所有的相關研究,因為他比先前的研究都還要複雜許多。因此有發表評論論文的期刊往往會有較高的影響因子。13

影響因子和學科領域有直接關係。

影響因子指標僅限於同一學科領域裡的期刊,不可跨學科使用。這是因為不同學科間的引用方式差異很大。14 例如,和數學相關的期刊因子都偏低,即使是最佳代表刊物也不例外。然而,和分子生物學有關的期刊一般都有較高的影響因子。

影響因子的計算數據並不對外公開。

期刊影響因子是湯森路透的產品之一。湯森路透是一間私人公司,沒有義務對外公開計算指標的數據和分析方法。至今,還沒有另一組織能成功預測或複製湯森路透所發表的影響因子報告。8

影響因子可以被操控。

編輯們可以利用各種方法來操控所屬期刊的影響因子。他們可以選擇刊登較多篇的評論文章和停止發表案例報告。前者因為能被大量引用而有助於提高影響因子,反觀後者則極少被引用。更糟的是,有些期刊編輯被發現,他們把論文退回給作者,並要求他們自我引述─即在論文裡引用該期刊發表過的其他論文。15

您知道嗎
孟德爾觀查碗豆8年,並發表了2篇相關的論文。然而,他的同儕無法了解其研究的重要性。40年後,他的生物遺傳定律才被de Vries和Correns重新發現,但孟德爾已逝世多年。
我們之前列出了幾個原因,向您解釋為何不該使用期刊影響因子做為測量研究品質的指標。如果贊助機構或您所屬的大學使用影響因子作為指標,我們建議您除了列出刊登您文獻的期刊的影響因子外,也列出你個別論文的h-指數和引用數據。不管刊登您文獻的期刊是否有權威性,這將有助於增加您文獻中論點的品質和影響力。

結論
最後,請切記,研究結果的影響力未必立刻能被學術界理解和接受。歷史上不少重要的研究發現都是在多年後,甚至是相關研究人員過世後才被承認的。要確定一份研究的真正價值不能單憑數值指標,更重要的是親自閱讀和複製其中的實驗以驗證該研究的真正價值。

Contributors


Why you should not use the journal impact factor to evaluate research

Eugene Garfield,1 the founder of the Journal Impact Factor (JIF), had originally designed it as a means to help choose journals. Unfortunately, the JIF is now often used inappropriately, for example, to evaluate the influence of individual pieces of research or even the prestige of researchers. This metric has recently come under considerable criticism owing to its inherent limitations and misuse.2-4

The impact factor of a journal is a simple average obtained by considering the number of citations that articles in the journal have received within a specific time frame.5 A previous article, “The impact factor and other measures of journal prestige” touched upon its calculation and features. This article delves a little deeper into the fallacies of the impact factor and points that you should consider when using it.

How the JIF should be used
  • As a measure of journal prestige and impact
  • To compare the influence of journals within a specific subject area
  • By librarians, to manage institutional subscriptions
  • By researchers, to identify prestigious field-specific journals to follow and possibly submit to
  • By journals, to compare expected and actual citation frequency and compare themselves with other journals within their field
  • By publishers, to conduct market research6
How the JIF should not be used
  • To evaluate the impact of individual articles and researchers
  • To compare journals from different disciplines
  • By funding agencies, as a basis for grant allocation
  • By authors, as a singular criterion of consideration for journal selection
  • By hiring and promotion committees, as a basis for predicting a researcher's standing
  • By authors, to compare themselves against their peers3,7

Characteristics of the JIF

Below are listed some of the features and shortcomings of the JIF that should be well understood in order to prevent misuse of this metric.

  • The JIF is a measure of journal quality, not article quality. The JIF measures the number of citations accrued to all the articles in a journal, not to individual articles. Following the well-known 80-20 rule, the top 20% articles in a journal receive 80% of the journal's total citations; this holds true even for the most reputed journals like Nature.8 So, an article published in a journal with a high JIF has not necessarily had high impact: it is very well possible that the article itself has not received any citations. Conversely, a few highly cited papers within a particular year can result in anomalous trends in a journal’s impact factor over time.9
Journal speak Journal impact factors are used only – and cautiously – for measuring and comparing the influence of entire journals, but not for the assessment of single papers, and certainly not for the assessment of researchers or research programs either directly or as a surrogate.- European Association of Science Editors10
  • Only citations within a two-year time frame are considered. The JIF is calculated considering only those citations that a particular journal has received within 2 years prior. However, different fields exhibit variable citation patterns. While some fields such as health sciences receive most of their citations soon after publication, others such as social sciences garner most citations outside the two-year window.11 Thus, the true impact of papers cited later than the two-year window goes unnoticed.
  • The nature of the citation is ignored. As long as a paper in a journal has been cited, the citation contributes to the journal’s impact factor, regardless of whether the cited paper is being credited or criticized.8,11 This means that papers being refuted or exemplified as weak studies can also augment a journal’s impact factor. In fact, even papers that have been retracted can increase the impact factor because, unfortunately, citations to these papers cannot be retracted.
  • Only journals indexed in the source database are ranked. Thomson Reuter's Web of Science®, the source database for the calculation of the JIF, contains more than 12,000 titles. Although this figure is reasonably large and is updated annually, several journals, especially those not published in English, are left out. Thus, journals not indexed in Web of Science don't have an impact factor and cannot be compared with indexed journals.12
  • Did you know?

    The impact factor for the Astrophysical Journal Supplement Series jumped from 6.247 in 2003 to 15.231 in 2004, owing to extremely high citation rates recorded for 13 papers in a special issue.
  • The JIF varies depending on the article types within a journal. Review articles are generally cited more often than other types of articles because the former present a compilation of all earlier research. Thus, journals that publish review articles tend to have a higher impact factor.13
  • The JIF is discipline dependent. The JIF should only be used to compare journals within a discipline, not across disciplines, as citation patterns vary widely across disciplines.14 For example, even the best journals in mathematics tend to have low IFs, whereas molecular biology journals have high IFs.
  • The data used for JIF calculations are not publicly available. The JIF is a product of Thomson Reuters®, a private company that is not obliged to disclose the underlying data and analytical methods. In general, other groups have not been able to predict or replicate the impact factor reports released by Thomson Reuters.8
  • The JIF can be manipulated. Editors can manipulate their journal's impact factor in various ways. To increase their JIF, they may publish more review articles, which attract a large number of citations, and stop publishing case reports, which are infrequently cited. Worse still, cases have come to light wherein journal editors have returned papers to authors, asking that more citations to articles within their journal〞referred to as self-citations〞be added.15

Did you know?

Gregor Mendel’s peers failed to grasp the significance of his 8-year-long experiment on peas and the 2 relevant papers he published. It was only 40 years later, after Mendel’s death, that deVries and Correns, recognized his work as depicting fundamental laws of inheritance.
These are some of the reasons you should not look at the JIF as a measure of research quality. It is important to explore other more relevant indicators for this purpose, possibly even in combination. If the JIF is used by a grant-funding body or your university, it might be a good idea to list your h index and citation counts for individual articles, in addition to the impact factors of journals in which you have published. This will help strengthen your argument on the quality and impact of your papers, regardless of the prestige of the journals you have published in.

Concluding remarks
Finally, remember that the nature of research is such that its impact may not be immediately apparent to the scientific community. Some of the most noteworthy scientific discoveries in history were recognized years later, sometimes even after the lifetime of the contributing researchers. No numerical metric can substitute actually reading a paper and/or trying to replicate an experiment to determine its true worth.
Contributors