Controlling Variables in Biology, Chemistry and Physics. Higher Competences Through Higher Content Knowledge? Empirical Evidence from Two Studies

Since the introduction of competences in the German national science standards the relation of competences and science content knowledge is discussed. Competences are defined as the ability of a person to solve specific problems in variable situations. According to a strict interpretation of this definition competences can be touched and measured in variable situations independent form specific scientific knowledge. C onsequently competence tests e.g. in the context of experimental competence are d esigned so that they not require any specific content knowledge. However, theoretical discussions and empirical findings show that content knowledge is important and crucial in the process of experimentation. This study investigates the relation of students’ ability to control variables in experiments and their science content knowledge in Biology, Chemistry and Physics. Data from two cross-sectional studies are analyzed by structural equation modelling. The results show that students’ content knowledge and not their number o f school years p redict their ability to control variables. This finding was consistent over all three subjects and two studies. We discuss the consequences of this finding for research and science teaching based on four possible interpretations. Furthermore we propose an experimental research design for that o ffers deeper understanding of the relation between competences and content knowledge.

Making inquiry-based science learning visible: The influence of CVS and cognitive skills on contentknowledge learning in guided inquiry

Many science curricula and standards emphasise that students should learn both scientific knowledge and the skills associated with the construction of this knowledge. One way to achieve this goal is to use inquiry-learning activities that embed the use of science process skills. We investigated the influence of scientific reasoning skills (i.e. conceptual and procedural knowledge of the control-of-variables strategy) on students’ conceptual learning gains in physics during an inquiry-learning activity. Eighth graders (n = 189) answered research questions about variables that influence the force of electromagnets and the brightness of light bulbs by designing, running, and interpreting experiments. We measured knowledge of electricity and electromagnets, scientific reasoning skills, and cognitive skills (analogical reasoning and reading ability). Using structural equation modelling we found no direct effects of cognitive skills on students’ content knowledge learning gains; however, there were direct effects of scientific reasoning skills on content knowledge learning gains. Our results show that cognitive skills are not sufficient; students require specific scientific reasoning skills to learn science content from inquiry activities. Furthermore, our findings illustrate that what students learn during guided inquiry activities becomes visible when we examine both the skills used during inquiry learning and the process of knowledge construction. The implications of these findings for science teaching and research are discussed.


Stender, A., Schwichow, M., Zimmerman, C. & Härtig, H. (2018) Making inquiry-based science learning visible: the influence of CVS and cognitive skills on content knowledge learning in guided inquiry, International Journal of Science Education.

What students learn from hands-on activities

The ability to design and interpret controlled experiments is an important scientific process skill and a common objective of science standards. Numerous intervention studies have investigated how the control-of-variables-strategy (CVS) can be introduced to students. However, a meta-analysis of 72 intervention studies found that the opportunity to train CVS skills with hands-on tasks (g¼0.59) did not lead to better acquisition of CVS relative to interventions without a hands-on component (g¼0.74). We conducted an intervention study in which we investigated the differential effects of hands-on and paper-and-pencil training tasks on 161 eighth-grade students’ achievement. CVS was demonstrated to all students before they were grouped into a hands-on or a paper-and-pencil training condition. In both training conditions, students designed and interpreted experiments about which variables influence the force of electromagnets. Students in the hands-on group interacted with physical equipment while students in the paper-and-pencil group planned experiments using sketches and interpreted the outcome of experiments presented in photographs. We found no general advantage or disadvantage of hands-on tasks, as both groups did equally well on CVS and content knowledge tests. However, hands-on students outperformed paper-and-pencil students on a hands-on test identical to the training tasks, whereas the paper-and-pencil students outperformed hands-on students on a science fair poster evaluation task similar to the paper-and-pencil training. In summary, students learned task-specific procedural knowledge, but they did not acquire a deeper conceptual understanding of CVS or the content domain as a function of type of training. Implications for instruction and assessment are discussed.

Schwichow, M., Zimmerman, C., Croker, S., & Haertig, H. (2016). What students learn from hands-on activities. Journal of Research in Science Teaching (JRST). 53(7). p.980-1002.

The impact of sub-skills and item content on students’ skills with regard to the control-of-variables-strategy

The so-called control-of-variables strategy (CVS) incorporates the important scientific reasoning skills of designing controlled experiments and interpreting experimental outcomes. As CVS is a prominent component of science standards appropriate assessment instruments are required to measure these scientific reasoning skills and to evaluate the impact of instruction on CVS development. A detailed review of existing CVS instruments suggests that they utilize different, and only a few of the four, critical CVS sub-skills in the item development. This study presents a new CVS assessment instrument (CVS Inventory, CVSI) and investigates the validity of student measures derived from this instrument utilizing Rasch analyses. The results indicate that the CVSI produces reliable and valid student measures with regard to CVS. Furthermore, the results show that the item difficulty depends on the CVS sub-skills utilized in item development, but not on the item content. Accordingly, previous instruments that are restricted to a few CVS sub-skills tend to over- or underestimate students’ CVS skills. In addition, these results indicate that students are able to use CVS as a domain general strategy in multiple content areas. Consequences for science instruction and assessment are discussed.

Schwichow, M., Christoph, S., Boone, W., & Haertig, H. (2016). The impact of sub-skills and item content on students’ skills with regard to the control-of-variables strategy. International Journal of Science Education (IJSE). 38 (2). p.216-237.

Teaching the control-of-variables strategy: A meta-analysis

A core component of scientific inquiry is the ability to evaluate evidence generated from controlled experiments and then to relate that evidence to a hypothesis or theory. The control-of-variables strategy (CVS) is foundational for school science and scientific literacy, but it does not routinely develop without practice or instruction. This meta-analysis summarizes the findings from 72 intervention studies at least partly designed to increase students’ CVS skills. By using the method of robust meta-regression for dealing with multiple effect sizes from single studies, and by excluding outliers, we estimated a mean effect size of g = 0.61. Our moderator analyses focused on design features, student characteristics, instruction characteristics, and assessment features. Only two instruction characteristics – the use of cognitive conflicts and the use of rule demonstrations – were significantly related to student achievement. Furthermore, the format of the assessment instrument was identified as a major source of variability between study outcomes. Implications for educational practice and future research are discussed.

Schwichow, M., Croker, S., Zimmerman, C. Hoeffler, T., & Haertig, H. (2016). Teaching the control-of-variables strategy: A meta-analysis. Developmental Review. 39. p.37-63.

Förderung der Variablen-Kontroll-Strategie im Physikunterricht

Damit Schüler/innen lernen selbstständig zu experimentieren, sollten im Unterricht Strategien der experimentellen Erkenntnisgewinnung thematisiert werden. Eine grundlegende Strategie der experimentellen Erkenntnisgewinnung ist die Variablen-Kontroll-Strategie(VKS). Der folgende Beitrag stellt ein VKS-Übungsexperiment zum Thema Leitfähigkeit sowie Merkmale von VKS-Übungsexperimenten und Befunde einer unterrichtlichen Erprobung in einer achten Jahrgangsstufe vor.

Schwichow, M., Christoph, S., & Härtig, H. (2015). Förderung der Variablen-Kontroll-Strategie im Physikunterricht. [Teaching the Control-of-Variables-Strategy in Physic Classes] Der mathematisch naturwissenschaftliche Unterricht (MNU). 68.(06).

Dissertation Schwichow, M. (2015): Förderung der Variablen-Kontroll-Strategie im Physikunterricht

The paper based dissertation of Martin Schwichow (2015) about teaching CVS in physics includes four published papers. (1) A meta-analysis of CVS interventions studies, (2) a paper about the development and validation of on CVS test instrument, (3) an intervention study that compares the effect of hands-on and paper-pencil training on students CVS skills and (4) a paper about the design of CVS training materials. The book is accomplished by a comprehensive introduction to the CVS in physics and a summary and discussion of all four papers (in German only). In addition the book includes an extended appendix of all teaching materials and test instruments.


Dissertation Schwichow, M. (2015): Förderung der Variablen-Kontroll-Strategie im Physikunterricht
Adobe Acrobat Dokument 5.7 MB

Das Waldschattenspiel - Nutzung eines kooperativen Brettspiels im Anfangsunterricht zur Optik

Das Waldschattenspiel ist ein kooperatives Brettspiel, das eine spielerische Auseinandersetzung mit den Phänomenen Licht, Schatten und Reflexion ermöglicht. Das Spiel eignet sich zum Einsatz im naturwissenschaftlichen Grundschulunterricht bzw. zum Einstieg in das Thema Optik in der 5. und 6. Jahrgangsstufe. Wie Lernspiele im Allgemeinen, so wirkt auch das Waldschattenspiel positiv auf die Schülermotivation und ermöglicht den Spielenden ein selbstständiges und kreatives Problemlösen (siehe Hendrik Härtigs Beitrag in diesem Heft). Die Entwicklung des Waldschattenspiels wurde durch die Waldorfpädagogik beeinflusst. Hier bilden Spiele einen Rahmen für die individuelle und aktive Entwicklung der Persönlichkeit sowohl auf kognitiver als auch auf emotional-affektiver Ebene. Das Waldschattenspiel schult kooperatives Handeln und ein aktives Miteinander, v.a. die gemeinsame Entwicklung und Umsetzung von Strategien und das Verfolgen gemeinsamer statt individueller Ziele.

Schwichow, M., & Kohnen, N. (2015). Das Waldschattenspiel. Nutzung eines kooperativen Brettspiels im Anfangsunterricht zur Optik. [The Forest Shadow Game. Utilizing a cooperative board game in optics introduction courses] Unterricht Physik. 149. P. 6.