Children’s acquisition and use of the control-of-variables strategy: effects of explicit and implicit instructional guidance

Direct instruction is a proven effective method to strengthen children’s ability to design unconfounded experiments using the control-of-variables strategy (CVS). Recent research suggests that task segmentation can also promote children’s use of this strategy. The present study investigated this assumption by comparing the relative effectiveness of both instructional approaches in elementary science classes. Children in the direct instruction condition (n = 22) were taught the CVS prior to investigating a multivariable inquiry task. Children in the task structuring condition (n = 23) were not, but received a segmented version of the inquiry task that addressed the variables in successive order. Children in the control condition (n = 22) investigated the multivariable inquiry task without additional support. Comparison among these three conditions revealed that task structuring equals direct instruction in effectiveness to promote children to use the CVS and draw valid inferences, and that either type of guidance is more effective than unguided inquiry learning. However, as children’s knowledge of the CVS improved as much in either condition, more practice seems needed for children to take full advantage of both instructional approaches.     

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.     

Children's and adults' evaluation of the certainty of deductive inferences,inductive inferences,and guesses

Two experiments investigated kindergarten through fourth-grade children's and adults' (N = 128) ability to (1) evaluate the certainty of deductive inferences, inductive inferences, and guesses; and (2) explain the origins of inferential knowledge. When judging their own cognitive state, children in first grade and older rated deductive inferences as more certain than guesses; but when judging another person's knowledge, children did not distinguish valid inferences from invalid inferences and guesses until fourth grade. By third grade, children differentiated their own deductive inferences from inductive inferences and guesses, but only adults both differentiated deductive inferences from inductive inferences and differentiated inductive inferences from guesses. Children's recognition of their own inferences may contribute to the development of knowledge about cognitive processes, scientific reasoning, and a constructivist epistemology.     

Effects of knowledge and display design on comprehension of complex graphics

In two experiments, participants made inferences from weather maps, before and after they received instruction about relevant meteorological principles. Different versions of the maps showed either task-relevant information alone, or both task-relevant and task-irrelevant information. Participants improved on the inference task after instruction, indicating that they could apply newly acquired declarative knowledge to make inferences from graphics. In Experiment 1, participants spent more time viewing task-relevant information and less time viewing task-irrelevant information after instruction, and in Experiment 2, the presence of task-irrelevant information impaired performance. These results show that domain knowledge can affect information selection and encoding from complex graphics as well as processes of interpreting and making inferences from the encoded information. They also provide validation of one principle for the design of effective graphical displays, namely that graphics should not display more information than is required for the task at hand.     

Searching and planning: young children's reasoning about past and future event sequences

Six experiments examined children's ability to make inferences using temporal order information. Children completed versions of a task involving a toy zoo; one version required reasoning about past events (search task) and the other required reasoning about future events (planning task). Children younger than 5 years failed both the search and the planning tasks, whereas 5-year-olds passed both (Experiments 1 and 2). However, when the number of events in the sequence was reduced (Experiment 3), 4-year-olds were successful on the search task but not the planning task. Planning difficulties persisted even when relevant cues were provided (Experiments 4 and 5). Experiment 6 showed that improved performance on the search task found in Experiment 3 was not due to the removal of response ambiguity.     

Inference making ability and its relation to comprehension failure in young children

Young children's reading comprehension skill is associated with their ability to draw inferences (Oakhill 1982, 1984). An experiment was conducted to investigate the direction of this relation and to explore possible sources of inferential failure. Three groups of children participated: Same-age skilled and less skilled comprehenders, and a comprehension-age match group. The pattern of performance indicated that the ability to make inferences was not a by-product of good reading comprehension, rather that good inference skills are a plausible cause of good reading comprehension ability. Failure to make inferences could not be attributed to lack of relevant general knowledge. Instead, the pattern of errors indicated that differences in reading strategy were the most likely source of these group differences.     

A combined approach to strengthen children’s scientific thinking: direct instruction on scientific reasoning and training of teacher’s verbal support

Inquiry-based lessons have been demonstrated to improve children’s scientific thinking (i.e. reasoning abilities and domain-specific knowledge). Although empirical evidence shows that inquiry-based learning requires instruction, research comes from two approaches that have not been bridged yet: direct instruction of scientific reasoning and teacher training of verbal support. We investigated how these two types of instruction separately or combined strengthened children’s scientific thinking by comparing four conditions: baseline, direct instruction, verbal support, and a combined approach. Effectiveness of an inquiry-based lesson series on scientific reasoning abilities, vocabulary, and domain-specific knowledge (near and far transfer) were studied among 301 fourth graders. Results showed that both approaches strengthened different components of scientific reasoning abilities, and that a combination of instructions was most effective for scientific reasoning abilities, vocabulary, and domain-specific knowledge. Domain-specific knowledge acquisition was strengthened only when both instructions were provided. It can thus be concluded that each type of instruction has unique contributions to children’s science learning and that these instructions complement each other. Our study thus showed that inquiry-based lesson series when preceded by direct instruction of scientific reasoning and scaffolded with verbal support are most effective.     

Two levels of inferential behavior in young children.

5- and 6-year-old children made inferences about the spatial locations of animals and people in a series of 3 experiments. The tasks employed manipulable models to represent the spatial relations involved and were made as simple as possible. 2 levels of inferential behavior were found. The first constituted the ability to draw an inference consistent with information given, but with minimal understanding of the way in which inferences can assist in decisions between alternative outcomes. At the second level, children succeeded in discriminating inferences which were logically necessary from those which were merely consistent with the premises. Most 5-year-olds were at the first level, most 6-year-olds at the second level. 2 criteria for the identification of young children's behavior as inferential were established, and the results of the present study were discussed in terms of recent related work with both younger and older children.     

Sequential effects of high and low instructional guidance on children’s acquisition of experimentation skills: Is it all in the timing?

We report the effect of different sequences of high vs low levels of instructional guidance on children’s immediate learning and long-term transfer of simple experimental design procedures and concepts, often called “CVS” (Control of Variables Strategy). Third-grade children (N = 57) received instruction in CVS via one of four possible orderings of high or low instructional guidance: high followed by high (HH), high followed by low (HL), low followed by high (LH), and low followed by low (LL). High guidance instruction consisted of a combination of direct instruction and inquiry questions, and low guidance included only inquiry questions. Contrary to the frequent claim that a high degree of instructional guidance leads to shallow learning and transfer, across a number of assessments—including a 5-month post-test—the HH group demonstrated a stronger understanding of CVS than the LL group. Moreover, we found no advantage for preceding high guidance with low guidance. We discuss our findings in relation to perspectives advocating “invention as preparation for future learning”, and the efficacy of “productive failure”.     

Reasoning in a reading context: Deductive inferences in basal reading series

This study examined three basal reading programs published by Heath (1989), Silver Burdett Ginn (1993) and Houghton Mifflin (1993), to determine how frequently logically necessary relationships are expressed in text used by basal readers, and whether direct instruction in making logically necessary inferences accompanies such expressions in basal reader series. The complete contents of the basal readers, from grades one through eight, and all teachers' instructions pertaining to content read by students, were examined for each series. Frequency counts made by independent raters indicated that readers of these three series have a steady and frequent rate of opportunities to make logically necessary inferences, and to observe such inferences being modeled by the text; no significant differences were found between any of the series in the number of such opportunities. We found that while children's reading materials clearly offer a natural context in which logical understanding may be constructed, instructions for teachers in the basal series we examined did not include directly teaching students to use this kind of reasoning in reading comprehension. Suggestions are offered for how such instruction might be integrated with current teaching strategies in inference-making.     

The relation between the control-of-variables strategy and content knowledge in physics in secondary school

The control-of-variables strategy (CVS) is considered a hallmark in the development of scientific reasoning. It holds that informative experiments need to be contrastive and controlled. Prior evidence suggests that CVS is connected to the acquisition of science content knowledge. In a cross-sectional study involving 1283 high school students (grades 5–13), we investigate whether students’ mastery of CVS is related to their science content knowledge in physics. A latent variable model indicates that CVS is substantially associated with students’ science content knowledge, even when controlling for common effects of general reasoning abilities. Substantial differences in students’ CVS skills and their science content knowledge exist between the lower grade levels in secondary school when students receive physics education. A latent profile analysis shows that the most difficult aspect of CVS is understanding the impact of confounding. This sub-skill emerges in late secondary school and it requires that students master more procedural sub-skills of CVS. These findings indicate that CVS and science content knowledge are closely related within secondary school science contexts. In addition, the findings emphasize that students show various distinct patterns of CVS skills. The identified skill patterns can inform researchers and science educators about the CVS skills that students typically show and thus can be utilized in inquiry activities in different school grades, while the CVS skills students are lacking might be trained in focused interventions.     

The development of distrust

Preschool-age children's reasoning about the reliability of deceptive sources was investigated. Ninety 3- to 5-year-olds watched several trials in which an informant gave advice about the location of a hidden sticker. Informants were either helpers who were happy to give correct advice, or trickers who were happy to give incorrect advice. Three-year-olds tended to accept all advice from both helpers and trickers. Four-year-olds were more skeptical but showed no preference for advice from helpers over trickers, even though they differentiated between helpers and trickers on metacognitive measures. Five-year-olds systematically preferred advice from helpers. Selective trust was associated with children's ability to make mental state inferences.     

Scientific reasoning during adolescence: The influence of instruction in science knowledge and reasoning strategies

The mechanism linking instruction in scientific topics and instruction in logical reasoning strategies is not well understood. This study assesses the role of science topic instruction combined with logical reasoning strategy instruction in teaching adolescent students about blood pressure problems. Logical reasoning instruction for this study emphasizes the controlling-variables strategy. Science topic instruction emphasizes variables affecting blood pressure. Subjects receiving logical reasoning instruction link their knowledge of blood pressure variables to their knowledge of controlling variables more effectively than those receiving science topic instruction alone—their specific responses show how they attempt to integrate their understanding.     

Facilitating Students’ Conceptual Change and Scientific Reasoning Involving the Unit of Combustion

This article reports research from a 3 year digital learning project to unite conceptual change and scientific reasoning in the learning unit of combustion. One group of students had completed the course combining conceptual change and scientific reasoning. The other group of students received conventional instruction. In addition to the quantitative data, six students from each group were interviewed to evaluate their conceptual change, correct concepts and scientific reasoning. Results indicate that the experimental group’s students significantly outperformed the conventional group on the Combustion Achievement Test (CAT), Scientific Reasoning Test (SRT) and Combustion Dependent Reasoning Test (CDRT). Moreover, the experimental group’s students use higher levels of scientific reasoning more frequently and changed their alternative concepts more successfully than did the conventional group. Furthermore, once the experimental group’s students’ successfully changed their conceptions, their concepts tended to be more stable than the conventional group’s students, even after the 6th week of learning. These results demonstrate that combining conceptual change and scientific reasoning indeed improves students’ conceptual change and scientific reasoning ability more effectively than conventional instruction.     

The Interaction of Domain-Specific Knowledge and Domain-General Discovery Strategies: A Study with Sinking Objects

Recent work on scientific reasoning has largely focused on either domain-specific content knowledge or domain-general reasoning knowledge. This study investigated the interaction between the 2 types of knowledge in a real-world domain in which strict control of variables was not possible. We used a context, sinking objects, in which 10-, 12-, and, 14-year-old children's strong a priori beliefs could be revealed by participant-designed experiments. The results showed that most children initially believed weight alone determined an object's sinking rate. Older, but not younger, participants typically viewed experimentation as a means of exploring the effects of attributes other than weight. However, experimentation did help all children to understand the effects of object shape and material on sinking rates. The results suggest a number of questions for further research, including how children come to understand experimentation as a matter of evaluation rather than demonstration, and the role of unexpected experimental results in driving conceptual understanding.     

Student Interpretations of Phylogenetic Trees in an Introductory Biology Course

Phylogenetic trees are widely used visual representations in the biological sciences and the most important visual representations in evolutionary biology. Therefore, phylogenetic trees have also become an important component of biology education. We sought to characterize reasoning used by introductory biology students in interpreting taxa relatedness on phylogenetic trees, to measure the prevalence of correct taxa-relatedness interpretations, and to determine how student reasoning and correctness change in response to instruction and over time. Counting synapomorphies and nodes between taxa were the most common forms of incorrect reasoning, which presents a pedagogical dilemma concerning labeled synapomorphies on phylogenetic trees. Students also independently generated an alternative form of correct reasoning using monophyletic groups, the use of which decreased in popularity over time. Approximately half of all students were able to correctly interpret taxa relatedness on phylogenetic trees, and many memorized correct reasoning without understanding its application. Broad initial instruction that allowed students to generate inferences on their own contributed very little to phylogenetic tree understanding, while targeted instruction on evolutionary relationships improved understanding to some extent. Phylogenetic trees, which can directly affect student understanding of evolution, appear to offer introductory biology instructors a formidable pedagogical challenge.     

Children's use of motives and intentionality in person perception and moral judgement.

Preschool, second-, and fifth-grade children watched films and heard stories which portrayed an actor who intentionally or accidentally injured another for either good or bad motives. After each film or story, children were interviewed to determine their understanding of the actor motives and the intentionality of his act and their moral judgements. The results suggest that children of all ages understood the concepts of motive and intentionality, but that the ability to make accurate inferences about motives and intentionality develops with age. Motives affected children's evaluations at all ages, but intentionality affected only grade school children's evaluations. The results for moral judgment were discussed in terms of a theory which included features of both cognitive-developmental and social learning explanations of moral development.     

First Possession,History, and Young Children's Ownership Judgments

It is impossible to perceive who owns an object; this must be inferred. One way that children make such inferences is through a first possession bias—when two agents each use an object, children judge the object belongs to the one who used it first. Two experiments show that this bias does not result from children directly inferring ownership from first possession; the experiments instead support an alternative account according to which the first possession bias reflects children's historical reasoning. In Experiment 1, eighty‐five 3‐ to 5‐year‐olds only based inferences on first possession when it was informative about the past. In Experiment 2, thirty‐two 5‐year‐olds based ownership judgments on testimony about past contact, while disregarding testimony about future contact.     

Young children's causal inferences

We report 2 experiments that show a striking development between the ages of 3 and 4 years in children's ability to make causal inferences about sequences of events. The task in the first experiment was to work out what had caused the change to an object that started out as odd (noncanonical) in 1 way and ended up as odd in 2 ways--starting, for example, as a broken cup and ending as a wet and broken cup. When asked to choose the instrument that had caused the change, 3-year-olds often selected the instrument that could have caused the initial state (a hammer, in our example) and not the instrument that would produce the change. 4-year-olds hardly ever made this mistake. In the second experiment, the 3-year-olds were able to make the correct choice when the change was from a canonical to a noncanonical state (cup-wet cup) but had much more difficulty when the change was from noncanonical to canonical (wet cup-dry cup). The difference was much smaller in the older group. The first of these tasks can be solved simply on the basis of knowledge that a particular instrument can cause a particular effect without reference to the initial state. The second task requires attention to the differences between initial and final state. We conclude that the ability to make genuine causal inferences develops between the ages of 3 and 4 years.