A four-stage model for learning critical thinking skills using multimedia has recently been proposed, and here the instructional effectiveness of this model is reported. The Design for Multimedia in Learning (DML) Model has four distinct stages; of brainstorming cooperative group learning using synchronous media, then lateral-thinking collaborative learning using asynchronous media, followed by hypotheses-testing collaborative asynchronous, and finally sharing experiential-learning cooperatively using synchronous media. Signified hypertext links were purposively designed to complement the cooperative or collaborative style for each related stage. Empirical validation found that, while graduate students and closely-guided small groups could complete all four stages, students at the undergraduate level could successfully move through only the first two stages.
1.1 Previous models of learning
Two significant Models have been proposed to identify the essential steps of learning critical thinking skills; one by Dewey and another by Brookfield.
Dewey  proposed five phases of reflective or critical thinking--(1) suggestions, in which the mind leaps forward to a possible solution; (2) an intellectualization of the difficulty or perplexity that has been felt (directly experienced) into a problem to be solved, a question for which the answer must be sought; (3) the use of one suggestion after another as a leading idea, or hypothesis, to initiate and guide observation and other operations in collection of factual material; (4) the mental elaboration of the idea or supposition (reasoning, in the sense in which reasoning is a part, not the whole, of inference); and (5) testing the hypothesis by overt or imaginative action.
Brookfield  proposed also five phases to develop critical thinking--(1) a triggering event; (2) an appraisal of the situation; (3) an exploration to explain anomalies or discrepancies; (4) developing alternative perspectives; and (5) integration of alternatives in ways of thinking or living.
However, the steps given in the above models do not correlate with each other. The steps are not clearly distinguishable, and indeed their processes need not be sequenced linearly. So these models are not sufficiently clear to constitute the basis of a syllabus. A new clear and practical model is needed to provide the theoretic basis for an intelligent syllabus for acquiring critical thinking skills using multimedia based on the distinct ways of learning.
1.2 The distinct ways of learning
There are four distinct ways of learning ; learning alone independently, alone individually, in a group cooperatively, and in a group collaboratively. Here it is important to distinguish cooperative learning from collaborative learning, in order to deploy these in the proposed new Model.
Cooperative learning essentially involves at least one member of the group who 'knows' the content soon to be learnt by the other(s). Learning takes place through the 'knower' repeating, reiterating, recapitulating, paraphrasing, summarising, reorganising, or translating the point to be learnt.
Collaborative learning follows a scientific process of testing out hypotheses. A participant publicly articulates his (or her) own opinion as a hypothesis and being open to the value of conflict allows this to be negated if possible by others, in which case the original participant or another offers up a modified or alternative hypothesis for public scrutiny. In collaborative learning, disagreement and intellectual conflict are desirable interactions. All participants share in co-constructing the new knowledge together, and this learning occurs inside the group as a type of consensus achieved through analysis and argument. In collaborative learning, there was no 'knower' prior to the learning process taking place (in contrast to the situation of cooperative learning. …