1. Introduction
In recent years, theorists and researchers in marketing have made great efforts to understand and explain the nature of marketing, especially in advertising which is the most important component in the marketing mix. Theoretical and empirical studies have enhanced our understanding of the nature of marketing mixes, such as advertising (Kotler and Keller 2016). Billions of dollars are annually spent on advertising throughout the world. Such huge costs need to meet considerable efforts in measuring the effectiveness of advertising. Traditional methods, such as self-reports, for predicting the success of advertising largely depend on the audience’s willingness and ability to describe the level of attention, feeling, preference, or future behaviors associated with the marketing campaign to which they have been exposed (Ghorbani, Ali Sara Sarahsari, 2017). Using the tools in neuroscience to measure behavioral responses can lead to more valid results in psychology, such as behavior prediction and cognitive patterns. A critical goal of psychology is to predict behavior and shape people’s reactions. Simultaneously, people’s behavioral tendencies can be identified through their likes or dislikes of advertisements as environmental stimuli (Chandwaskar, 2018). In neuromarketing, as an interdisciplinary science, recognizing and predicting such behaviors and the ability to shape people’s reactions can be achieved by manipulating the stimuli. Combining the tools of neuroscience with advertising as a recurring stimulus can help people better understand their emotions and needs. Applying self-reports to measure consumers’ behavior, including questionnaires and face-to-face or telephone interviews, may lead to invalid results because of the limitations and biases that are inherent in conscious and unconscious processes. For example, unconscious processes occur subliminally and below the threshold of consciousness, and the conscious part of the human brain begins to function approximately 300 or 400 ms after the stimulus is presented; therefore, it cannot provide reliable verbal reporting while the human brain has already processed the data.
Nevertheless, these subconscious processes may significantly impact the audience’s behavior. People sometimes experience vague feelings of being exposed to advertisements. However, they may not be able to retrieve the information quickly from their memory and express it verbally. Similarly, people’s emotional experiences with advertising are complex and often involve automated processes that are difficult to achieve in self-report (Li, 2019).
Because of the great interest of advertising experts in identifying the decision-making mechanism of the audience and understanding their internal intentions, theories and models used in research have dramatically changed in the past few years (Ghorbani, et al., 2017). Researchers and experts have been looking for innovative and mixed methods to study consumers’ decision-making mechanisms to help increase the effectiveness of commercial and non-commercial advertising messages. Therefore, the use of neuroscience methods in marketing has recently become popular for they directly study the cortical activity at a certain time, place, and frequency (Wawrzyniak, 2016).
Although it is inaccessible for traditional marketing methods, such as self-report measures, there is progressively valid evidence proving that neuromarketing techniques can reveal the data showing that decisions are usually made based on emotions rather than rationality. Even logical decisions are impossible to make without emotional aspects (Ambler, Kokkinaki, & Puntoni, 2004).
Advertising is destined to achieve its social, educational, and commercial goals. Given the relatively high cost of content production and advertising, the presence of a large number of competitors, as well as the advertising bombardment, advertising agencies need to reach their target community optimally and effectively and have a favorable impact on consumers’ attitudes and decisions following the commercial and non-commercial goals (Ghorbani, et al., 1400). This effect can only occur by creating both attractive and memorable ads. To achieve this goal, it is necessary to evaluate the ads carefully. However, very few studies have been done on the effectiveness of advertising and banner structures. In this regard, the present study was conducted to inspect various studies to identify factors related to the effectiveness of neuromarketing advertisements in a systematic review. The findings of this research can be practically generalized in motivating the teaching, accuracy, and better understanding of educational materials and the conscious and unconscious processing of textbooks or health messages.

2. Participants and Methods
This descriptive study systematically reviews the factors related to the effectiveness of neuromarketing advertisements. A systematic review is a structured search performed according to predetermined rules and regulations. The statistical population of this systematic study includes all quantitative studies on the effectiveness of neuromarketing advertisements published in Science Direct, Scopus, Scholar Google, and Emerald databases. The search was done with a time limit of 1990 to 2021. The following keywords were searched in the title of the articles; “Advertising model”, “Neuromarketing”, “Advertisement effectiveness”, and “Consumer decision”. Because of no Persian articles in this field, only English articles published in international journals were considered. At each step, the searched articles in each database were entered into the Endnote software. A total of 900 articles were obtained using the mentioned keywords. The criteria for selecting articles in this study were the following two items: 1) published in reputable scientific databases in English; 2) related to the topics of the effectiveness of neuromarketing advertisements.
Review articles, qualitative studies, studies without discussion of neuromarketing, descriptive literature, and studies without measurement tools were excluded from the research process. Finally, 90 articles from 1990 to 2021 were included in the study. They were analyzed in detail, and their information was extracted and entered into the ready database. The process of searching and selecting articles is shown in Figure 1.

3. Results
At first, 900 articles were identified from various databases, of which 300 met the inclusion criteria. Among them, 210 articles were excluded from the study because they lacked experimental studies; at last, 90 articles were selected for the final review. All studies are summarized in Table 1.

Most studies have focused on the effectiveness of advertising in the field of neuromarketing. The ads reviewed in these articles contained commercial, social, and educational messages. Evidence from the study showed that the 37 related factors to the effectiveness of neuromarketing could result in changing the attitude and affecting the consumers’ decisions. The above-mentioned factors are listed in Table 1.

4. Discussion 
In this study, we reviewed the articles that investigate the motivational factors of advertisements in the field of neuromarketing in a systematic review. All the studies in this review used tools in neuroscience such as electroencephalography, functional magnetic resonance imaging, electrodermal activity, and so on to detect the influential factors influencing consumers’ decisions. The results showed that 37 factors in neuromarketing advertisements have essential roles in changing the consumers’ attitudes and decisions; namely, cognitive and conscious information, social and cultural values, symbols of authenticity and background, after-sales service, draw attention, simplicity, simple scenario, negative emotions, desirability or pleasantness, memory, unconscious decisions, cognitive decision making, shock, familiar and routine elements, age, gender, socio-economic level, narration, positive valence or positive emotions, product engagement, excitement, content and message relevancy, innovation, arousal, unpredictability, humor, brand or product display repetition, the place of the logo, timing, fear, surrealistic images, use of text, price, the voice of the speaker, audio symbols, music, and background music. The results indicate that considering all the factors in designing an advertisement can increase the impact of the ad on the attitude of the audience. Using these factors by creating arousal, activating brain processing, and recording in memory can lead to desirable changes in the consumers’ attitude toward the brand, the product, health-social messages, or the educational content.
According to the results, the most influential factors in the research were “drawing attention” and “positive emotions”, with 13 cases. Accordingly, the most emphasis on an advertisement’s effectiveness is on the stimuli that activate attention and positive emotions. Therefore, embedding stimuli related to attention draw (innovative ad presenting, placing an irrelevant and unexpected image or element, humorous factors such as irrelevance, imitation, irregularity, unreasonable repetitions, and funny appearances) and stimuli of positive emotions (joy, interest, and pleasure) can enhance the effectiveness of the advertisement.
Based on the results, memory was an influential factor in research with 11 cases. Therefore, it can be pointed out that the more desirable the advertisement is perceived, the more likely it is to be recalled. More excitement and arousal in the ads result in better recall. The results show that negative emotions, including sadness, anger, confusion, fear, and shock, were effective factors in 9 cases, which implies that negative emotions can also be stimulated for the effectiveness of advertising.
Subsequently, the following model can be derived from the components obtained from the systematic review in the form of main and sub-components and presented in the following proposed model. In this model, the components of positive and negative emotions are in the main category of emotions. Verbal and written expression, after-sales service, product features, price, and relevancy are in the main category of informing factors. Factors such as age, gender, cultural and social values ​​, and socio-economic level fall into the main category of demographic features. Logo place, familiar and routine elements, speaker’s voice, timing, number of displays, and simplicity fall into the category of ad structure. Music, humor, narrative, and deconstruction fall into innovation category.

Limitations and suggestions
Considering that neuromarketing is an emerging and interdisciplinary science, the number of articles in the field on the effectiveness of neuromarketing advertisements is very small. On the other hand, each research about determining the effect of commercial and non-commercial advertisements has examined the limited factors separately each time. No research was available in the form of measuring the effectiveness of advertising or as a review that comprehensively summarizes the factors affecting the change of attitude because of advertising. 
Also, there was no research providing an effective advertising model. The factors mentioned in this study have each been measured in a separate study using the tools in neuroscience. Some studies have only used neuromarketing tools to measure effectiveness, while more reliable results can be obtained if a combination of traditional measures, self-report, and consumer neuroscience tools are used. In addition to summarizing the factors influencing the design of an effective advertisement, the present study has provided a comprehensive model for advertising in neuromarketing. The derived model, the combination and integration of components from the review study, can be used as a conceptual research model in designing and measuring the effectiveness of commercial and non-commercial advertisements (medical, social, and educational). Therefore, it is suggested that the model’s components be measured, improved, and developed using electroencephalogram and electrodermal activity measurements. In this way, the lack of an effective advertising model for consumers’ decisions will be filled. 
It can also be acknowledged that the model mentioned above can be evaluated by structural equation modeling and the Delphi method to validate the components with the opinion of experts and specialists. It is also possible to level the components by interpretive structural modeling. In this regard, with the DEMATEL method, the effect of the components can also be identified. It is also suggested that the proposed model be evaluated in a separate study, specifically in motivational advertisements for teaching, accuracy, and a better understanding of educational materials and conscious and unconscious processing of the courses or health messages.

5. Conclusion
In this study, we tried to demonstrate that neuromarketing studies have a better and more accurate estimation of essential factors in advertising which affect people’s attitudes and decision-making. Since one of the essential concerns in psychology is to recognize, predict, and shape behaviors as well as to help people to know the factors, especially the unconscious factors, that influence their decision-making, it is critical to use valid and reliable methods, which is the combination of traditional self-report measures and tools in neuroscience.
The results show that the most influential factors in the research were “drawing attention” and “positive emotions”. “Memory” and “negative emotions” were other influential factors.  Accordingly, to create a compelling message to be broadcasted through an advertisement, the most emphasis needs to be on the stimuli that activate “attention” and “positive emotions”. Therefore, designing stimuli related to attention draw (such as innovation, placing an irrelevant or unexpected image, humorous factors, and funny appearances) and stimuli of positive emotions (joy, interest, and pleasure) would result in the advertisement’s effectiveness. Applying desirable and exciting elements can stimulate people’s memory to recall the message more easily. Embedding images and scenes associated with “negative emotions” (including sadness, anger, confusion, fear, and shock) can also make the message very effective.
The research findings are practical in creating educational materials considering the factors of the proposed model to make the most impression, better recalling lessons, and enhancing motivation in students and teachers. In addition, considering the factors mentioned above when designing ads conveying health or social messages would influence people’s attitudes and decisions toward more favorable ones. 

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be considered in this research.

Funding
The paper was extracted from the PhD. dissertation of the first author, Department of Business Administration, University of Payame Noor.

Authors' contributions
All authors equally contributed to preparing this article.

Conflict of interest
The authors declared no conflict of interest.


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