دانشگاه اصفهان تحقیقات بازاریابی نوین 2228-7744 16 3 2026 09 23 Effects of tDCS and Packaging Transparency on Decision-Making Time and Purchase Intention for Food Products تأثیر تحریک فراجمجمه‌ای با جریان مستقیم (tDCS) و شفافیت بسته‌بندی بر زمان تصمیم‌گیری و تمایل به خرید محصولات غذایی 79 114 30566 10.22108/nmrj.2026.148145.3297 FA احمد فلاحی استادیار گروه علوم ورزشی، دانشکده علوم انسانی، دانشگاه زنجان، زنجان، ایران امید مهدیه دانشیار گروه مدیریت، دانشکده علوم انسانی، دانشگاه زنجان، زنجان، ایران جابر علیزاده گورادل استادیار گروه روانشناسی، دانشکده علوم انسانی، دانشگاه زنجان، زنجان، ایران مینا شیری یکتا دانشجوی کارشناسی ارشد روانشناسی‌شناختی، دانشکده علوم انسانی، دانشگاه شهید بهشتی، تهران، ایران شمیم مقصودی ولنی دانشجوی کارشناسی گروه نقاشی، دانشکده هنر و معماری، دانشگاه زنجان، زنجان، ایران Journal Article 2026 01 25 This study aimed to investigate the effects of transcranial direct current stimulation (tDCS) and packaging transparency on decision-making time and purchase intention for food products, considering product type (healthy vs. unhealthy). This research employed a between-subjects experimental design and randomly allocated 63 students to four groups (control, sham, Fz, FPz). Stimulation was applied at 2 mA for 10 minutes over Fz or FPz regions according to the international 10-20 EEG system. Images of two products (chips as an unhealthy product and peanuts as a healthy product) in both transparent and non-transparent packaging were presented in pairs. Total reaction time (sum of time for two choices), purchase intention, and transparent packaging preference were measured. Findings revealed that active tDCS significantly increased decision-making time compared to the control group, while sham stimulation had no significant effect. Furthermore, choosing transparent packaging was associated with higher purchase intention, and this relationship remained stable after controlling for self-selection bias (using analysis of covariance), but was not influenced by tDCS stimulation. The main effect of product type was also significant (η²p = 0.24); preference for transparent packaging was significantly greater for healthy products compared to unhealthy ones, and this pattern was uniformly observed across all groups. Results indicate that although tDCS increases decision-making processing time, it has a direct but limited impact on purchase intention. In contrast, packaging transparency and product healthiness play a more determining role in predicting consumer purchase intention. Introduction Packaging has evolved beyond its traditional protective function to become a strategic marketing and communication tool that substantially influences consumer decision-making at the point of purchase. Transparent packaging, in particular, has received increasing attention because it allows consumers to directly inspect product contents, thereby enhancing perceptions of quality, freshness, authenticity, and purchase intention. Despite growing evidence regarding its positive effects on consumer attitudes and purchasing behavior, previous research has primarily relied on self-reported measures and has paid limited attention to objective behavioral indicators, such as decision time. Decision time represents an objective measure of cognitive effort and information processing during choice and provides a deeper understanding of consumer decision-making than subjective evaluations alone (Ratcliff & McKoon, 2008). Furthermore, although neuroimaging studies have identified several brain regions involved in value-based decision-making, they have been unable to establish causal relationships. Transcranial Direct Current Stimulation (tDCS), a non-invasive brain stimulation technique, enables researchers to investigate the causal contribution of specific cortical regions by temporarily modulating neural excitability (Nitsche & Paulus, 2000). Accordingly, this study examined whether stimulation of two prefrontal regions (FpZ and Fz) influences consumers' decision time, transparent packaging preference, and purchase intention when selecting transparent versus opaque packaging for healthy (peanuts) and unhealthy (potato chips) food products. Materials and Methods This applied study employed a laboratory-based experimental design with a mixed factorial structure incorporating both between-subject and within-subject factors. Data were collected during February 2025 at the Neuromarketing Laboratory of the University of Zanjan. The between-subject factor was the type of brain stimulation, including four experimental conditions: (1) control (no stimulation), (2) sham stimulation, (3) active stimulation of the frontal midline region (Fz), and (4) active stimulation of the frontopolar region (FpZ). The within-subject factor was product type, consisting of one healthy food product (peanuts) and one unhealthy food product (potato chips). Initially, 72 undergraduate students volunteered to participate in the study. Participants who met the inclusion criteria, including normal or corrected-to-normal vision, regular consumption of packaged food products, and no medical contraindications for transcranial direct current stimulation (tDCS), were randomly assigned to the four experimental groups using balanced block randomization. After screening for incomplete responses and outliers in reaction-time data, the final sample consisted of 63 participants. Brain stimulation was administered using a battery-powered constant-current tDCS device. Following established safety and stimulation protocols, a direct current of 2 mA was applied for 10 minutes through saline-soaked sponge electrodes (35 cm²) positioned according to the international 10–20 EEG system (Nitsche & Paulus, 2000). In the sham condition, the current was gradually increased and decreased during the initial seconds before being discontinued, thereby producing the sensation of stimulation while controlling for placebo effects. Immediately after stimulation, participants completed a computerized choice task. They were sequentially presented with paired images of transparent and opaque packages for each product in a counterbalanced order. The packaging designs were identical in all respects except transparency, and no brand names or logos were displayed to eliminate brand-related bias. Participants selected their preferred package for each product, while the system automatically recorded the total decision time from the presentation of the first stimulus until completion of the final choice. Following the experimental task, participants completed a questionnaire measuring transparent packaging preference and purchase intention using five-point Likert scales adapted from previous packaging research. To enhance internal validity, the study controlled for placebo effects through sham stimulation, minimized individual differences by random assignment, standardized the stimulation protocol and laboratory environment, counterbalanced stimulus presentation, and used anonymous product designs. Ethical approval was obtained from the Ethics Committee of the University of Zanjan (IR.ZNU.REC.1403.025), and written informed consent was obtained from all participants before data collection. Research Findings Data from 63 participants were included in the final analyses after outlier removal. Descriptive statistics indicated that the four experimental groups were comparable in terms of age and gender distribution, and all assumptions required for parametric analyses were satisfied. To address the first objective, a one-way ANOVA examined the effect of transcranial Direct Current Stimulation (tDCS) on decision time. The results revealed a significant main effect of stimulation condition on reaction time (F(3,59) = 5.77, p = 0.002, partial η² = 0.23), indicating a relatively large effect size. Bonferroni post hoc comparisons showed that participants in both active stimulation groups (FpZ and Fz) exhibited significantly longer reaction times than those in the control group (FpZ vs. Control: p = 0.002; Fz vs. Control: p = 0.016), whereas the sham stimulation group did not differ significantly from any of the other groups. No significant difference was observed between the two active stimulation conditions. The second objective investigated the effects of stimulation condition and selected packaging type on purchase intention while controlling for differences in transparent packaging preference. The overall ANCOVA model was significant (F = 4.98, p < 0.001) and explained 43.5% of the variance in purchase intention (Adjusted R² = 0.435). Packaging choice exerted a strong main effect (F = 22.58, p < 0.001, partial η² = 0.475), whereas neither stimulation condition (F = 0.84, p = 0.476, partial η² = .048) nor the interaction between stimulation condition and packaging choice (F = 0.70, p = 0.647, partial η² = 0.078) reached statistical significance. Participants who selected transparent packaging for both products reported significantly higher purchase intention than those who selected opaque packaging for both products, while those selecting one transparent and one opaque package also demonstrated greater purchase intention than participants consistently choosing opaque packages. No significant difference was observed between the "both transparent" and "one transparent–one opaque" groups. To examine the third objective, a mixed-design repeated-measures ANOVA assessed whether the effect of product type on transparent packaging preference was moderated by tDCS. A significant main effect of product type was found (F(1,59) = 31.14, p < 0.001, partial η² = 0.345), indicating that transparent packaging was preferred significantly more for the healthy product (peanuts) than for the unhealthy product (potato chips). However, neither the main effect of stimulation condition (F = 1.10, p = 0.359, partial η² = 0.054) nor the interaction between product type and stimulation (F = 0.40, p = 0.757, partial η² = 0.020) was statistically significant. The preference for transparent packaging remained consistently higher for the healthy product across all experimental groups. Overall, the findings indicate that prefrontal brain stimulation significantly altered the temporal dynamics of consumer decision-making by increasing decision time, whereas transparent packaging remained the primary determinant of purchase intention. Furthermore, transparent packaging was consistently more effective for healthy food products than for unhealthy products, irrespective of the stimulation condition. Discussion of Results and Conclusions The findings provide new evidence regarding the cognitive and neural mechanisms through which packaging transparency and non-invasive brain stimulation influence consumer decision-making. First, active transcranial Direct Current Stimulation (tDCS) significantly increased decision time without altering purchase intention or packaging preference. This finding suggests that prefrontal stimulation primarily affected the temporal dynamics of information processing rather than the final valuation of alternatives. Such a pattern is consistent with cognitive information-processing theories, which propose that longer reaction times reflect greater cognitive effort, enhanced evaluation of competing alternatives, and increased executive control rather than changes in the final choice. It is also consistent with evidence indicating that prefrontal tDCS modulates executive functions and decision-related processing without necessarily changing behavioral outcomes (Dedoncker et al., 2016). Interestingly, no significant difference was observed between stimulation over the FpZ and Fz regions. Although these cortical areas are associated with distinct cognitive functions, including metacognitive evaluation, conflict monitoring, and executive control, the results suggest that, within the context of packaging evaluation, they may operate as components of an integrated prefrontal control network. This functional convergence implies that visually guided purchase decisions rely on coordinated executive processing rather than on isolated regional activity. Second, transparent packaging emerged as the strongest predictor of purchase intention regardless of stimulation condition. This finding reinforces previous research demonstrating that transparent packaging enhances perceived quality, freshness, and consumer trust by reducing information asymmetry and allowing direct inspection of the product (Simmonds & Spence, 2017; Simmonds et al., 2018a). The persistence of this effect after controlling for individual differences in packaging preference further supports the proposition that packaging transparency functions as a powerful visual quality signal influencing purchase decisions. Finally, consumers expressed significantly stronger preferences for transparent packaging when evaluating the healthy product than the unhealthy product, while brain stimulation did not moderate this relationship. This pattern supports perceived value theory (Zeithaml, 1988), suggesting that visual access to the product is particularly valuable when consumers associate transparency with naturalness, freshness, and healthfulness. Overall, this study demonstrates that packaging transparency and prefrontal brain stimulation influence different components of consumer decision-making. Whereas transparent packaging directly increases purchase intention, tDCS primarily affects the cognitive processing underlying decision formation. These findings contribute to neuromarketing theory by distinguishing between cognitive processing time and purchase valuation and offer practical implications for designing transparent packaging strategies, particularly for healthy food products. هدف این مطالعه بررسی تأثیر تحریک فراجمجمه‌ای با جریان مستقیم (tDCS) و شفافیت بسته‌بندی بر زمان تصمیم‌گیری و تمایل به خرید محصولات غذایی با در نظر گرفتن نوع محصول (سالم-ناسالم) بود. این پژوهش از طرح آزمایشی بین‌گروهی استفاده کرد و ۶۳ دانشجو در چهار گروه (کنترل، تحریک ساختگی، Fz، FPz) به‌صورت تصادفی تخصیص یافتند. تحریک با شدت ۲ میلی‌آمپر به‌مدت ۱۰ دقیقه روی نواحی Fz یا FPz مطابق با سیستم بین‌المللی ۱۰-۲۰ EEG اعمال شد. همچنین، ضمن نمایش تصاویر دو محصول (چیپس به‌عنوان محصول ناسالم و بادام‌زمینی به‌عنوان محصول سالم) در دو نوع بسته‌بندی شفاف و غیرشفاف به‌صورت جفت‌شده، زمان واکنش کل (مجموع زمان دو انتخاب)، تمایل به خرید، و ترجیح بسته‌بندی شفاف نیز اندازه‌گیری شد. یافته‌ها نشان داد تحریک واقعی tDCS موجب افزایش معنادار زمان تصمیم‌گیری نسبت به گروهِ کنترل شد، درحالی‌که تحریک ساختگی تأثیر معناداری نداشت. همچنین، انتخاب بسته‌بندی شفاف با تمایل به خرید بیشتر همراه بود و این رابطه پس‌از کنترل سوگیری خودانتخابی (با استفاده از تحلیل کوواریانس) پایدار ماند؛ اما تحت‌تأثیر تحریک tDCS قرار نگرفت. اثر اصلی نوع محصول نیز معنادار بود (0.24η²p=)؛ ترجیح برای بسته‌بندی شفاف در محصولات سالم به‌طور معناداری بیشتر از محصولات ناسالم بود و این الگو در تمامی گروه‌ها به‌صورت یکنواخت مشاهده شد. نتایج نشان می‌دهد tDCS زمان پردازش تصمیم‌گیری را افزایش می‌دهد؛ اما تأثیر مستقیم و محدودی بر تمایل به خرید دارد. در مقابل، شفافیت بسته‌بندی و سلامت محصول نقش تعیین‌کننده‌تری در پیش‌بینی تمایل به خرید مصرف‌کننده ایفا می‌کند.

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