Same Decisions Are More Probable to Be Correct

Bias in perceptual decisions comes to pass when the advance knowledge colluded with the current sensory evidence in support of the final choice. The literature on decision making suggests two main hypotheses to account for this kind of bias: internal bias signals are derived from (a) the residual of motor response-related signals, and (b) the sensory information residues of the decisions that we made in the past. Beside these hypotheses, a credible hypothesis proposed by this study to explain the cause of decision biasing, suggests that the decision maker neuron can make use of the residual information of the previous decisions for the current decision. We demonstrate the validity of this assumption, first by performing behavioral experiments based on the two alternative forced-choice discrimination of motion direction paradigms. Secondly, by making use of the fitted models based on accumulation to the bound mechanism. In both cases, previous trial's trace can be seen on the current decision. Results indicated the probability of being correct in current decision increases if the previous decision is towards the current decision. Also, the model keeps the previous decision information, provides a better fit to the behavioral data. Our findings suggest that the state of decision variable which is represented in the activity of decision maker neurons after crossing the bound (in the previous decision) can accumulate with the decision variable for the current decision in consecutive trials.