A psychological experiment for quantitative evaluation of degree of external opinions influencing the choice of a participant in conditions of uncertainty was suggested. A computer-driven experiment was performed, with 256 participants. In the experiment participating volunteers were shown a series of images accompanied by two not-evident alternative answers for a question “what is this?”, and were prompted to make their choice under different condition. These conditions were: (i) a free individual choice (control group); (ii) a choice when each participant sees the results of real answers of other subjects of his experimental group (“true” group); (iii) a choice when the participants see false response promptings generated by a special computer program (“false” groups). Quantitative results were obtained showing an influence of “psychological pressure” to a frequency of occurrence of alternative answers. A laser-like model is presented for energy levels in a brain and for decision making in such conditions. The laser-like model is based on a usual system of kinetic equations describing dependence of population of excited and ground levels (before and after the answer, respectively), and the number of different answers (zero known answers for control group, number of real or manipulated answers for "true" and "false" groups). By fitting parameters of the model to results of the experiment, numerical values of parameters of the model (“coefficients of stimulating influence” analogues to Einstein coefficients Bik for stimulated emission of radiation) were determined.