Investment decision processes come in many forms. There is the lone wolf portfolio manager that has the ability to make decisions without input or approval from others. There will be constraints on his behavior but not explicit collaboration. The team or committee approach is often employed by larger money management firms that have longer investment horizons. This is more likely to occur with asset allocation decisions. Finally, there is the quantitative approach where a systematic model will generate the investment decisions. Of course, a committee or PM will likely oversee the decisions from the model. what is not often discussed with group decisions is the process of persuasion to achieve consensus.
Any group decision requires persuasion. Unfortunately, building consensus requires understanding the minds of the other decision-makers in the room. This is a skill or a consideration not generally discussed. Nevertheless, there has been interesting research on describing or classifying the decision-makers that will have to be sold to reach a conclusion. This classification scheme can be condensed in the Miller-Williams decision-making style matrix.
Any good presenter should be aware of the different types of decision-makers in his audience; however, this means investment decisions will be driven by a narrative and not just the output from a model.