Walnuts are rich in many cognitive enhancing nutrients. Walnuts specifically have been shown in a variety of studies to reduce cognitive decline from aging (Haider et al., 2011; Joseph, Shukitt-Hale, and Willis, 2009; O'Brien et al., 2014; Poulose and Shukitt-Hale, 2013; Rajaram et al., 2017; Willis et al., 2008). They're rich in Vitamin E, omega-3, anthocyanins, antioxidants, zinc, and polyphenols all crucial in cognition.
Sources