The TPB was developed as an extension of the Theory of Reasoned Action (TRA) ^[1][8]. Into this theory, Ajzen added a construct referred to as “perceived behavioral control” (PBC) as a determining factor for both behavioral intention and the behavior itself. While the earlier theory (TRA) comprised attitudes and subjective norms, TPB introduced and added the concept of perceived behavioral control (PBC), which was originally defined as an individual’s perception of the ease or difficulty of performing a particular behavior ^[2][9]. PBC is thus deemed influential in determining whether the individual will engage in the behavior or not. The inclusion of this variable has been found to increase accuracy in predicting behavior that is not under volitional control ^[3][10].

Based on the TPB, intentions for (willingness to perform) a behavior are determined by three variables. The first variable is attitudes, which constitute an individual’s overall evaluation of behavior. The second variable is subjective norms, which consist of a person’s beliefs about whether significant others think he/she should engage in the behavior. The third variable measures the extent to which the individual perceives that the behavior is under their personal control and is labeled PBC. Ajzen ^[1][8] and Madden et al. ^[3][10] reported empirical evidence that PBC significantly improves predictions of both intentions and behavior. Hence, the evidence is broadly supportive of the TPB in helping to understand and predict behaviors, including travel and tourism behavior.

In the TPB, intention is the immediate precursor of behavior, and is assumed to be based on attitude toward the behavior, perceived social pressure or subjective norms, and perceived behavioral control. A significant number of empirical researchers in tourism have shown that the TPB efficaciously predicts tourist behavior in various tourism contexts ^{[4][5][6][7][8][9][10][11][12][13]}[11,12,13,14,15,16,17,18,19,20]. However, the TPB does not take into account some important variables, such as the motivation that initiates tourists’ behavior in visiting places, and other perceptual factors. Therefore, the current study added motivation and perceived safety and security factors to study their individual and collective roles in tourists’ visit behavior.

The intention of tourists’ consumption behavior is regarded as an important research topic in tourism ^[14][21]. Travel intention denotes an individual’s commitment to travel or intent to travel. It can be viewed as an outcome of a psychological process that leads to transforming travel motivation into behavior, thus, a travel action. Jang et al. ^[15][22] noted that only limited empirical research has previously attempted to investigate the role of intention in the travel motivation–behavior relationship, leaving intention as one of the least researched areas of tourism. Iso-Ahola ^[16][23] associated leisure behavior with attitude, while Qu and Ping ^[17][24] assessed the link between the intention of Hong Kong residents to undertake cruise tours and their motivation. In both cases, a positive relationship was established. Shim et al. ^[18][25] also conducted a study and found that a more positive tourists’ affective attitude corresponded to a stronger intention towards future travel. Separately, Hennessey et al. ^[19][26] attributed the intention to travel to two major elements of tourism marketing: responses to advertising and the respondent’s use of official tourism websites.

The above studies suggest that travel intention may be influenced by multiple factors, including motivations, attitude, and promotion. Beldad and Hegner ^[20][27] have noted that new explorations continue to be focused on understanding how demographic characteristics, motivation, and cultural factors can also influence intention. The theory of planned behavior (TPB) introduced later by Ajzen ^[1][8] added the third predictor of behavioral intention to the TRA, calling it perceived behavioral control (PBC). This theoretical context has been applied in the understanding of travel intention as a kind of behavioral intention. It is, therefore, clear that in the psychology of human behavior, behavioral intention is widely acknowledged as the immediate antecedent to behavior, including travel behavior.

Attitude refers to “the degree to which a person has a favorable or unfavorable evaluation or appraisal of the behavior in question” ^[1][8] (p. 188). In consumer studies, it is described as the enduring, one-dimensional summary evaluation of a product or brand that is assumed to energize buying behavior ^[21][28]. Following the “principle of compatibility” ^[22][29], attitudes predict behavior. Ajzen and Fishbein ^[23][30] viewed attitude as a disposition to respond with some degree of favorableness or unfavorableness to a psychological object. According to them, attitudes are expected to predict and explain human behavior through behavioral intention, whereby positive attitudes should predispose approach tendencies, whereas negative attitudes should predispose avoidance tendencies. Travel attitude has been found to impact on tourists’ intention to visit ^[24][25][31,32]. In applying this to consumer behavior studies, attitude and beliefs are also responsible for brand images formed in buyers’ minds that affect their buying behavior ^[26][33].

Subjective norms are beliefs about the normative expectations of others that tend to exert perceived social pressure on an individual to have tendencies towards behaving, or actually behaving, in a certain manner ^[1][8]. This construct is widely considered in studies that apply the TPB, including travel and tourism research, for example ^{[27][28][29][30][31][32]}[34,35,36,37,38,39]. However, some earlier tourism studies that followed the TPB model have found subjective norms not to have significant impact on leisure-related visit intention ^[29][30][36,37].

Perceived behavioral control denotes how people perceive the easiness or difficulty of performing a behavior of interest ^[1][8]. This factor is responsible for enabling or disabling the execution of behavioral goals. Many studies have supported the view that behavioral intention is produced from a combination of attitude toward the behavior, subjective norms, and perceived behavioral control (for example, ^[33][34][40,41]). According to TPB, the more favorable a person’s attitude is towards a behavior and subjective norms, and the greater the perceived behavioral control, the stronger that person’s intention will be to perform the behavior in question ^[33][40]. Therefore, the more people are able to have control over the opportunities and resources they have to perform a specific behavior, the more likely they will engage in such a behavior.

2. Modifying TPB by Extension

The accuracy of the predictive ability of TPB for many different behaviors has been supported by many studies ^[35][42]. However, some other studies recommend adding more predictors to the theory, in order to increase its explanatory ability ^{[36][37][38][39]}[43,44,45,46]. Therefore, this researchtudy integrated the additional factors of motivation and perceived safety and security into the proposed model, used to examine willingness to visit historical heritage sites. By integrating these additional variables into the TPB, the explanatory power of predicting visit behavioral intention was expected to improve, without significantly affecting the three original TPB constructs, as explained below. Motivation is one of the significant research topics covered in a number of studies in tourism research ^[40][41][42][47,48,49]. Most of these studies recognize the dynamism and heterogeneous nature of client motivation by considering tourist activities and individual personality relationships. Some authors, like ^[43][50], believe that, due to the dynamic concept of motivation, there is a possibility of identifying different tourist profiles based on these variables. Based on the social psychology point of view, the motives that compel a person to make a certain decision are closely connected to expectations which may result in great personal satisfaction ^[44][51]. Interestingly, literature on the choice behavior of tourists also indicates that motivation and “need” are interrelated ^[45][52]. They argue that tourists are attentive to stimuli that satisfy their desires and ignore stimuli that are not relevant to satisfaction of their desires and needs. Hsu and Huang ^[28][35] pointed to a paucity of research relating motivations and intentions to visiting tourist destinations and went ahead to discover that motivation had a positive influence on intention.  The protection motivation theory (PMT) ^[46][53] proposed a modified version of expectancy-value theories, focusing on risk perception and change of intention. The theory postulates three crucial components of fear appeal: (i) the magnitude of the noxiousness of an environment; (ii) the probability of an event’s occurrence; and (iii) the efficacy of a protective response. Protective motivation arises from these three components of fear appeal. Travel-related risks include, but are not limited to, cultural and language difficulties, natural disasters, terrorism, political instability, hygiene, diseases, crime and accidents, and environmental quality ^[47][48][54,55]. In relation to tourism, Sonmez and Graefe ^[49][56] established that an increase in cases of aviation accidents, crime, and terrorist activities represented danger and prompted careful selection of safe destinations, taking extra precautions while traveling to risky destinations, or canceling travel plans, among tourists. Destinations perceived as risky by potential tourists are avoided for those they consider safe. Buigut ^[50][57] has shown that terrorism has indeed significantly affected tourist arrivals and tourism earnings in Kenya.