# Psychological Effects of Sweet Taste and Sweet Taste Preference
## 4 Sweet Taste Preference and Obesity
While some studies found support for a negative relationship between BMI and sweet (and other) taste perceptions [38; 39; 40], other studies found no effects [41; 42; 43; 44], or even reported rather enhanced than reduced sweet taste sensitivity [45; 46]. These mixed results may be at least partly explained by different approaches to measure taste [47]. Furthermore, an age-related general and gradual decline in the ability to detect sweet taste has to be considered as well [48]. However, the known age-related changes in sweet taste preferences (with higher sweet taste preferences in children and adolescents) cannot be explained by those changes [49]. Thus, further research is required. Humans and animals may prefer sweet taste in contrast to, for example, bitter taste perhaps due to evolutionary reasons (see above), but it still remains unclear whether we may have learned the preference for sweet (or other) tastes in early childhood (or even in utero) or maybe acquire this liking later in life. A systematic review on in utero and early infant taste experiences and later taste preferences found no clear results. A \"potential programming of sweet taste acceptance\" was found only in studies with long-term exposure to sweet taste (or short-term exposure with immediate testing) [50]. Brain imaging studies (as well as animals studies) showing an activation of the reward system related to sweet stimuli have gained attention, and have even led to an analogy between sugar and addictive drugs, such as cocaine [51]. So, what are the neural representations of our preference for sweet taste? Sweet stimuli processing has been shown to activate brain regions, such as the primary gustatory cortex (insula), postcentral gyrus, and thalamus [52], but an activation of the orbitofrontal cortex, a well-known part of the reward circuit of the brain, has also often been reported [53; 54]. Here, it is important to stress that other studies may not have reported activation because functional brain activity in this region is difficult to detect due to the high susceptibility of signal drop out in standard fMRI protocols. Furthermore, a number of factors in the experimental design may affect the observation of reward-related brain areas in relation to sweet taste [55]. However, several studies demonstrated that sweet stimuli may result in rewarding and craving similar to (or even higher than) addictive drugs [51; 56]. This may reflect evolutionary arguments (see above) and might explain why many individuals have difficulty controlling the consumption of sweet foods. Given that the taste of sweet snacks may feel much more rewarding, for example, when feeling hungry, context factors may be important when investigating the relationship between sweet taste and activation of reward-related brain regions. A recent meta-analysis of fMRI studies has found moderating effects of the relationship between sweet stimuli and activation of the reward system. The authors report that hunger, but not fasting or BMI, was linked to sweet stimuli-related activation of the reward circuit (orbitofrontal cortex and ventral striatum) in the brain [54]. The research on psychological effects of sweet taste, as well as the research discussed in this chapter, refers to sweet taste induced by different snacks (e.g., [21]) or other sweet foods (e.g., [33]). Do the results differ when nonnutritive sweeteners instead of natural sweets are used? Given that an increasing number of people try to replace nutritive sweeteners with nonnutritive sweeteners to address their desire for sweet taste with reduced calories, this question seems to be important. For the psychological effects of sweet taste on romantic mindsets or prosocial behavior, the role of nonnutritive sweeteners remains unclear, since there are no studies in this research area.