In most developed countries, the proportion of single person households is dramatically increasing while traditional, multi-person households are shrinking [1]. In the U.S., the number of single person households has reached 35 million (28%), the second largest type of household after two person households [2]. Single person households are the leading type of household in a survey of 28 European countries, accounting for one-third (34%) of total households [3]. The growth in single person households is expected to continue, such that they will exceed 40% of total households in many countries [1]. The growing number of singles is thought to be fueled by an increase in late marriages, divorces, widows and widowers, single elderly, and voluntary single life choices, which are related to extended lifespans and more individualized lifestyles [4, 5].

Parallel to this phenomenon, the number of solo restaurant diners is also growing. Research notes that solo consumers spend longer time periods outside the home during the day due to education or career responsibilities, dual-career demands, and reductions in size of social networks (in personal relationships, as well as community and social organizations) [4, 5]. In the hospitality and tourism industry, these phenomena have led to an increase in solo diners. In fact, consumers are eating alone in more than half of their dining occasions [6], and an increased number of parties of one are found in restaurants [7]. Considering the long-term potential of the solo dining population for driving market change and boosting sales in the industry, the unique characteristics of solo diners and their subsequent behavioral patterns compared to group diners warrant examination.

Previous studies examining the difference between solo and group diners' food consumption mostly focused on the amount of food consumed or the meal duration, in which the consumption did not occur in a restaurant setting (i.e., social facilitation of eating) [8]. Other studies on eating out alone have explored feelings and experiences of solo diners indepth but the studies were limited to qualitative analyses of a few individuals [9, 10] or focused on a particular gender [11], lacking generalizability to a broader population. More recently, quantitative approaches have examined solo diners' restaurant visit intentions [12], dining experiences [13], and anticipated satisfaction [14], yet the studies provided solo diners' perspectives only, lacking a comparison with group diners, thus their varying menu-decision making processes are not known.

Therefore, to address these research gaps, this study sought answers to the following questions: (1) Do solo diners in restaurants make different menu item decisions compared to group diners?; (2) If so, what are the underlying cognitive mechanisms that lead to the different menu decisions?; and (3) Are the different menu decisions contingent upon certain external conditions such as menu nutrition information? Specifically, consumer psychology studies in the marketing field often examine food choices by comparing relatively rational choices (i.e., healthier foods) to relatively more emotional choices (i.e., less healthy, more indulgent foods) [15]. Building on this literature, this study focused on how solo dining may lead to different preferences for healthier versus indulgent menu items compared to group dining.

This study's arguments are based primarily on the self-control dilemma and temporal construal theory. The self-control dilemma (or self-regulation) reflects the conflicts between the higher order, long-term goal with a future benefit and a lower order, short-term goal with an immediate benefit [16, 17]. Temporal construal theory describes that the activation of a distal temporal construal leads to greater self-control compared to the activation of a proximal temporal construal; that is, people's temporal focus on the future help them behave in a way that is more aligned with their longterm goals, resisting the temptation that yields immediate pleasure [16, 17, 18, 19]. While these theories are well-established concepts in psychology and marketing literature and widely used in healthy vs. indulgent food consumption contexts [15, 20, 21], they have rarely been used in restaurant contexts. Thus, in application of these concepts, we propose that solo diners are more likely to select healthier (vs. indulgent) menu items than group diners based on the activation of a distal (vs. proximal) temporal construal resulting from the lack (vs. presence) of dining partners.

This study also assessed whether the effect is mediated by solo diners' pursuit of utilitarian (vs. hedonic) consumption orientation compared to group diners [5], and whether the effect is conditioned on the amount of nutrition information in the menu [22]. That is, it is plausible that consumers with dining partners may enjoy more experiential dimensions of restaurant dining that result in pleasure and excitement (i.e., hedonic consumption), while solo dining may be more associated with calmness and the achievement of necessary goals such as fulfilling basic food needs (i.e., utilitarian consumption) [5, 23, 24, 25, 26, 27, 28]. Such difference in consumption orientation between solo and group diners may lead to their different menu item decisions. Also, an external condition such as the provision of menu nutrition information may lead to different results of healthy choices for solo vs. group diners due to their increased awareness of healthy levels of menu items [22, 29, 30, 31, 32, 33]. Taken together, this study examined the effect of dining social context on healthy vs. indulgent menu item intentions, mediated by consumption orientation, and moderated by the amount of nutrition information on menus in a casual dining restaurant setting.

Driven by the increasing popularity of solo dining, this study examined the effect of dining social context (solo vs. group dining) on healthier and less healthy, indulgent menu item choices in casual dining restaurants based on the self-control dilemma and temporal construal theory. Furthermore, the mediating role of consumption orientation (utilitarian vs. hedonic) and the moderating role of the amount of menu nutrition information in the decision-making process were also examined. The findings showed that: first, solo diners are more likely to be oriented to a utilitarian consumption, while group diners are more likely to be oriented to a hedonic consumption; and second, controlling for the level of nutrition involvement, solo diners are more likely to eat healthier foods in restaurants than group diners. More specifically, solo (vs. group) diners showed (1) lower (vs. higher) intentions to order less healthy, indulgent items due to a utilitarian (vs. hedonic) consumption orientation, irrespective of menu nutrition information conditions, and (2) higher (vs. lower) intentions to order healthy items when the menu included calorie, fat, and sodium information about the menu items.

The findings offer useful information to both researchers and managers by examining the menu-decision making processes of solo and group diners, particularly regarding healthy vs. indulgent menu items, by exploring the roles of consumption orientation and nutrition information on menus. Theoretically, the findings contribute to an enhanced knowledge of solo diners' menu-decision making processes compared to group diners in restaurants. Previous studies on solo dining examined only solo diners' restaurant visiting intentions [12], general dining experiences and feelings [9, 10, 11, 13], and anticipated satisfaction [14]. This study compared solo diners with group diners and showed how the dining social context leads to different menu choices with varying levels of healthiness.

Specifically, findings confirmed that solo diners seek more utilitarian consumption experiences, while group diners seek more hedonic consumption experiences, consistent with prior hospitality and consumer studies [5, 28]. Furthermore, the activation (vs. deactivation) of hedonic orientation in group (vs. solo) diners subsequently resulted in stronger (vs. weaker) intentions of ordering less healthy, indulgent menu items, supported by healthy food choice studies [21, 23]. In regard to the amount of menu nutrition information conditions, the disclosure of more nutrition information such as fats and sodium in addition to calories strengthened the effect of dining social context on healthy menu item intentions (i.e., a stronger intentions of solo diners and less intentions of group diners) compared to no or only calorie information conditions, congruent with previous nutrition labeling studies highlighting the differential impacts of nutrition labeling for different consumers [22, 29, 30]. Specifically, the finding that disclosing more nutrition information leading to more healthy choices for some consumers and less healthy choices for the other consumers is similar to Byrd et al. [43], which found that disclosing more nutrition (sodium) information led to healthier (low sodium) choices for consumers with a positive taste intuition and less healthier (high sodium) choices for consumers with a negative taste intuition. This finding may be of importance to the public health studies and practices.

It is also important to note the differential impacts of eating alone on healthy eating results depending on the contexts. That is, several health studies have pointed out unhealthy dietary behaviors (e.g., skipping the meal), unhealthy weight status (i.e., overweight or underweight), or increased likelihood of abdominal obesity and metabolic syndrome among men who frequently eat alone [44, 45]. Other studies reported mixed associations between healthy or unhealthy dietary intakes and the elderly individuals living alone who also likely eat alone frequently [46, 47]. It may be also possible that solo diners with a primary goal of convenience would rather choose quick-service restaurants as a dining place and eat more processed fast foods that are less likely to be healthy. However, using self-control concepts, we showed that people are more likely to make healthier choices when dining alone than dining together when eating alone occurs in a full-service restaurant context. This finding is congruent with an interview study which showed that people associates healthy eating in restaurants with solo than group dining due to an increased self-control ability when alone [48].

On the other hand, the findings also revealed noteworthy non-differences. First, while the results were consistent with the hypothesized directions (i.e., solo diners' stronger preferences for healthy items, group diners' stronger preferences for indulgent items), the single effect of dining social context was not statistically significant in terms of the menu item ordering intentions of solo and group diners. We found that this effect was in fact qualified by the significant interaction between dining social context and the amount of nutrition information, and thus, it is essential to consider the nutrition information conditions in the interpretation of the findings. More specifically, the effect of dining social context on healthy item intentions was contingent upon the amount of nutrition information conditions such that differences in ordering intentions were not statistically significant until the menu provided calories, fats, and sodium information. That is, a greater amount of nutrition information on the menu allowed solo diners to accomplish their healthier choice goal as compared to group diners. This finding may be a concern for the current nutritional labeling policy in restaurants (i.e., mandatory calorie labeling in chain restaurants) [31] in that the provision of only calorie information, including no information, may be not enough to inform consumers of the healthiness or unhealthiness values of the meals they intend to have.

Second, it is important to note that the mechanism leading to an intention to select healthy menu items is different from the mechanism that leads to an intention to select less healthy, more indulgent menu items, as well as the interactions of the nutrition information with these mechanisms. Consumption orientation was only a significant mediator for the effect of dining social context on indulgent menu item intentions, but not for the effect on healthy menu item intentions. In other words, a hedonic (vs. utilitarian) consumption orientation led to more (vs. less) indulgent item intentions but a utilitarian (vs. hedonic) consumption orientation did not necessarily lead to more (vs. less) healthy item intentions. On the other hand, the amount of nutrition information only affected the impact of dining social context on healthy menu item intentions, not indulgent menu item intentions. Thus, these findings provide a new understanding beyond earlier marketing studies that considered the decision-making processes between healthy vs. indulgent foods as merely dichotomous and opposite [20, 23]. The findings especially point to the need for more research in healthy vs. indulgent food decisions using different mechanisms for each of the selection of healthy and indulgent foods. Lastly, the indirect effects of dining social context on healthy and indulgent item intentions through consumption orientation were stable across the amount of nutrition information conditions. Thus, the finding notes that, while an increase in the amount of nutrition information helps the healthy item decisions of consumers with preferences for healthy menu items (i.e., solo diners in this study setting), it does not necessarily facilitate the healthy vs. indulgent choices of utilitarian vs. hedonic consumption-oriented consumers (e.g., hedonic consumption-oriented group diners pursuing indulgent items).

For restauranteurs, findings highlight the relative utilitarian values of solo diners in comparison to the relative hedonic values of group diners, subsequent indulgent meal preferences of group diners in general, and healthy meal preferences of solo diners when more nutrition information is provided on menus. Restauranteurs thus can obtain operational insights from the findings into the impacts of the voluntary labelling of additional nutrition information beyond calories on restaurant menus or their mandatory labelling in certain areas (e.g., fat, sodium, and carbohydrates in Oregon State) [49]. It is said that the best restaurant menus are the ones that provides a variety of choices to meet both healthy and indulgent meal interests of diverse consumers. However, a focus on healthier menu offerings might be particularly valuable for restaurants that specifically expect a higher percentage of solo diners, such as those located in or close to airports and conference centers for solo business travels and university towns for routine convenience solo diners, to fulfill their utilitarian and healthy eating goals. The disclosure of more nutrition information would be a plus for the segment to clearly identify the healthiness of the meals and to show more preferences for those items. On the other hand, restaurants primarily targeting couples, families, and friends, such as those located in holiday travel destinations, amusement parks, and higher-end casual dining restaurants for holiday or celebratory dining, may largely benefit from a wide range of indulgent menu offerings that can satisfy the hedonic consumption goals of the group diners. The provision of calorie or additional nutrition information on menus may possibly draw the group diners' attention on indulgent menu items. Thus, each restaurant should decide on the amount of nutrition information they wish to provide on menus depending on the customer mix of group to solo diners for maximum profits as well as the government regulations.

Several limitations need to be noted in understanding the findings of this study. First, vegetarian menu options were not considered in this study. Considering that only 5% of American adults identify themselves to be vegetarians [50], animal protein sources were used in our menu. However, as vegetarian meals are growing in popularity and respect for diverse food preferences is important, it would be worth examining how the inclusion of vegetarian menu options could impact the current findings. Second, while his study limited itself to the setting of a casual dining restaurant to increase the internal validity of the study, whether healthy eating outcomes vary with other types of restaurants is worth further investigation. Lastly, future studies may wish to vary the composition of dining partners in group dining and examine how it impacts the differences between solo and group dining. While this study set the group dining context to eating with two to three, generalized dining partners based on the most common party size in restaurants, other research may wish to focus on group dining with larger groups or different dining contexts such as romantic couples vs. business dining groups vs. family groups. In these contexts, social norms or impression management mechanisms may be of consideration to determine group diners' varying preferences.

This study addressed answers to the research questions of: (1) Do solo diners in restaurants make different menu item decisions compared to group diners? – Yes; (2) If so, what are the underlying cognitive mechanisms that lead to the different menu decisions? – Different consumption orientations; and (3) Are the different menu decisions contingent upon certain external conditions such as menu nutrition information? – Yes. In summary, the findings showed solo (vs. group) diners' lower (vs. higher) intentions to order less healthy, indulgent menu items through a utilitarian (vs. hedonic) consumption orientation mechanism, and higher (vs. lower) intentions to order healthy menu items when nutrition information including calorie, fat, and sodium content was presented on the menu. Thus, while one might consider solo dining as unhealthy and negative experiences due to a lack of the joy of dining with company, this study showed that solo dining may rather lead to healthier choices through a greater self-control and a utilitarian, goal-oriented mindset. Plus, the solo mealtime may be blissful with an unexpected joy of dining with an important but neglected company: yourself!