This paper reports on a preregistered study aimed at testing for executive function differences across individuals who self-reported one of four distinct dietary patterns: No Diet, No Sugar, Vegetarian, and Mediterranean Diet patterns. The incentivized decision task involves Bayesian assessments where participants may use existing (base rate) as well as new information (sample draw evidence) in making probability assessments. Sample size, hypotheses, and analysis plans were all determined ex ante and registered on the Open Science Framework. Our hypotheses were aimed at testing whether adherence to a specialty diet improved decision making relative to those who reported following No Diet. Our data fail to support these hypotheses. In fact, we found some evidence that adherence to a No Sugar Diet predicted a reduced decision accuracy and was connected to an increased imbalance in how the participant weighted the two sources of information available. Our results suggest that decision making is nuanced among dietary groups, but that short-term incentivized decisions in an ecologically valid field setting are likely not improved solely by following a promoted diet such as the Mediterranean or Vegetarian diet.