Aprendizaje del concepto de variable como incógnita a lo largo de la escuela secundaria

To answer the first research question, two types of research collaboration - the number of authors and the number of countries - significantly associate with increased citations in most categories and fields. The number of authors significantly associates with increased citations in all categories and broad areas except for Physics. The extent to which this factor associates with increased citation counts differs across the domains and it seems that it is less important for subject categories with a higher propensity for research collaboration, such as Space Science. The number of countries is significant for increased citations in all subject categories and fields except for Computer Science, Economics & Business, Engineering, Mathematics, Microbiology, Multidisciplinary, Neuroscience &

168

Behaviour, Physics, Psychology/Psychiatry, Social Sciences, General, and Space Sciences. There is substantial multicollinearity among the research collaboration factors in Physics and this may be the reason that the number of authors and the number of countries are not important factors for citation counts in this area.

The number of institutions associates with decreased citations or is an insignificant factor for citation counts even though it associates with increased citation counts in all categories when separately modelled. Nevertheless, this factor significantly associates with increased citation counts in Clinical Medicine and Social Sciences, General. Overall, it seems that the number of institutions contributing to a collaboration is unimportant even though it may appear to be important if it is modelled separately from the number of collaborating authors. In other words, the citation benefit of multi-institutional collaboration is probably due to the extra authors involved rather than due to the extra institutions involved.

For the second question, author impact is a significant factor for citation counts in all categories and broad areas. Institutional impact is a significant determinant of increased citation counts in all categories and broad areas except for Mathematics and Physical Sciences. However, the factor association with increased citations is weak (average 0.1% for an increase from the lower to upper quartile in MNCS scores). The unexpected results in the two subject areas may result from the limitations of the measure used to quantify institutional prestige. Country impact is a significant factor of increased citation counts and decreased zero citations in all the categories and an increase from the lower to upper quartile in the factor associates with an average 50% increase in the citation counts.

169

To answer the third question, journal and reference characteristics are significant determinants of increased citations to articles in all subject categories and broad areas. The Journal Impact Factor (JIF) very significantly associates with increased citation counts and decreased zero citations in all categories and fields and the percentage increase in the citation counts for each unit increase in JIF averages 20%. It seems that the JIF contribution to an increase in citation counts is higher in subject areas with a lower average journal Impact Factor such as Social Sciences, General. Reference impact significantly associates with increased citations to articles in the majority of categories except for Mathematics. Perceiving the cited work as a classic reference written by a well-known researcher in the field and using a comprehensive overview of high-impact literature are two recognised motivations for citations (Case & Higgins, 2000; Shadish, Tolliver, Gray, & Sengupta, 1995), showing that the intellectual content of a paper may not be the only reason why it is cited. Articles published in more international journals in terms of geographic dispersion of publishing authors receive more citations in most categories except for Biology & Biochemistry, Microbiology, Neuroscience & Behaviour, and Space Science. Articles using more international references in terms of geographic dispersion of authors also receive more citations in most categories except for Agricultural Sciences, Computer Science, Environment/Ecology and Immunology whereas reference citer internationality is not a good determinant of citation counts. Excessive multicollinearity was found for these factors in most fields, and this may have negatively affected the results of simultaneous models. The number of references

170

is also associated with increased citation counts in all categories and fields, although it is not a significant factor for zero citation in a number of categories.

To answer the fourth question, field size associates with increased citation counts in a number of fields, but is an insignificant determinant of either citation counts or zero citations in most categories and broad areas. This may be due to an ineffective measure of field size being used, however. Among the article size attributes, title length significantly associates with decreased citation counts in most categories showing that articles with shorter titles receive a higher number of citations whereas abstract length significantly associates with increased citation counts in all categories except for Agricultural Sciences, Economics & Business, Engineering, and Mathematics. Article length is not a good determinant of

increased citations in Biology & Biochemistry, Microbiology, and

Multidisciplinary but significantly associates with increased citations in all the other categories.

For the fifth question, abstract readability is not an important factor for citations in the majority of categories except for Social Sciences, General, in which it associates with increased citations.

To answer the sixth question, research funding was only modelled in the four broad areas due to data limitations. Based on the results, funded articles receive more citations in Physical Sciences, Life Sciences and Medicine but not in Social Sciences.

171