INTRODUCTION Cognitive tools could be defined as computational applications that are designed to support, extend and enhance thinking processes (Elsayed & Qiu, 2006). Representations of different kinds are also supposed to reduce cognitive load of learners. The aim of an educational representation is about communicating a specific message from an expert to a novice. According to Jakobson’s communication model (1960), there are six factors of communication that are needed to occur: context, addresser, addressee, contact, common code, and message. Although the model was developed to describe verbal acts of communication, it has a more general field of application, as it involves common code. In communication, we are not limited to using words and can actually use anything that functions semiotically, e.g. in instruction different kinds of visual representations are widely used to communicate knowledge. As context plays an important role in communication, it is crucial that while developing new digital learning objects (LOs), we supply them with sufficient contextualization elements. Visual literacy advocates stress that although in schools teachers are dealing with communication of new knowledge to students, verbal information is the one dominantly used to convey messages. However, in overall communication we heavily use visual modality, and therefore this should be the case in learning and instruction as well. Advocates of learning styles (visual, auditory, kinesthetic-tactile) would probably add that auditory modality is best for auditory learners, however visual learners are then somewhat neglected. Speaking about fields of natural sciences, e.g. chemistry, we are talking about a visual science. And without being visually literate it is very hard to understand the essence of chemistry at its sub-microscopic level. As communication is about manipulating signs, one of our aims was to see how well the students were able to make sense of the LOs they saw on the screens. Our second aim was to find out if students were able to translate information from a model which is more familiar to them applying more abstract and unfamiliar LOs of another model. METHODS The sample was composed of 100 students of 8th grade (age 14-16). Two interactive web-based models (Chemical Bonds http://bio.edu.ee/flash/keemside/index.htm and Oxides http://mudelid.5dvision.ee/oksiidid) were used in the study together with student worksheets of Chemical Bonds and Oxides. Learners were provided with specific instructions and tasks which they had to follow in a prescribed order and answer content-specific questions in-between and during the tasks. Such tasks were meant to help learners to create referential connection between the symbolic and sub-microscopic levels of representations. On the worksheets, learners were provided with tasks involving LOs from one model and were asked to map referential features of those onto LOs of the second model. This method was used in order to foster development of coherent understanding of the chemistry domains which is possible only when learners are able to translate visual information from language of one presentation to that of another using adequate domain-specific context. FINDINGS Our findings clearly show that even though before the application of models and worksheets the majority of students (66%) did not cope with translation of visual information from one model to another, the situation was different after the treatment. The post-test results clearly show that the students were statistically significantly (p<0.001) better in encoding information using visual code of an unfamiliar kind, as 69% of students succeeded. This finding gives us the prove which is also hinted at by other researchers, that actually visual literacy is and should be developed through curriculum which enables learners to manipulate visuals in a more intensive manner. At the same time, the fact that students were able to translate information from one model to another also showed that students developed a coherent understanding in and across studied topics as the tasks were both visual and domain-specific. Special attention in our models was on providing learners with sufficient context prior to the usage of models. However, do the students possess sufficient awareness of the contextual information? If context as one of the communication factors is left out, then this leads to miscommunication and development of misconceptions. In this respect our findings showed statistically significant (p<0.001) development in understanding of chemistry in both topics studied. From this, we concluded that students were able to gain sufficient awareness of the learning objects in the models. This finding is in good accordance with Jaakkola and Nurmi (2004) and Heyes (2006) studies, where creating appropriate context for LOs was found to be crucial aspect in increasing the effectiveness of learning. Overall we may conclude that while developing and applying new LOs, the decisive focus should be on supplying them with sufficient contextualization elements as well as supporting development of visual literacy.

learning objects, contextualization elements, visual literacy, cognitive tools