I. Method

A single-factor (message interactivity: none, low, medium, and high) between-subjects online experiment was conducted to test the hypotheses and research questions.

II-1. Participants and procedure 

A total of 113 undergraduate students in a university in Chuncheon, South Korea were recruited for this experiment approved by the institutional review board at the university. After signing the informed consent form and sharing their preexisting attitudes toward PM, participants were randomly assigned to one of four versions of a website, each with a different degree of message interactivity. They were instructed to fully browse the linked website, spending as much time as needed, and then fill out a post-experiment questionnaire. The entire study session took 20–25 minutes. Participants were 62.8% female, and the average age was 21.56 years old, ranging from 18 to 28 years old.

II. Literature review

II-1. Heuristic-systematic model (HSM)

Dual-process theories, such as the heuristic-systematic model (HSM; Eagly & Chaiken, 1993) and the elaboration likelihood model (ELM; Petty & Cacioppo, 1986), explain that individuals use two different modes of information processing. In both models, individuals think deliberately about the persuasive information they are given through extensive cognitive efforts (i.e., a systematic and central route) or they count on heuristic/peripheral cues (e.g., length of message, credibility of spokesperson, and statistics) with limited cognitive effort, depending on their motivation and ability to process information (Eagly & Chaiken, 1993; Griffin et al., 1999; Petty & Cacioppo, 1986).

While peripheral and central routes of processing in ELM are mutually exclusive, which means individuals choose between the two (Petty & Cacioppo, 1986), the two HSM routes of processing can co-occur (Chaiken et al., 1989). HSM, developed as an alternative to ELM, holds three hypotheses. First, the attenuation hypothesis proposes that one route can attenuate the other route, meaning that when systematic processing increases, heuristic processing weakens (Chaiken et al., 1989). Second, the additivity hypothesis describes systematic processing and heuristic processing as independent, meaning that both types of processing can increase at the same time (Maheswaran et al., 1992). Third, the bias hypothesis asserts that heuristic cues, such as experts’ credibility, can bias one’s judgment and affect systematic processing (Chaiken & Maheswaran, 1994).

III. Measures and Research Model 

IV. Result

The purpose of this study was to examine how message interactivity featured on a PM website affects behavioral intention in a variety of ways. This study results that the “more message interactivity more systematic processing” relationship stopped at a certain point are quite interesting. In additions show that message interactivity enhanced systematic processing whereas heuristic processing was not related to message interactivity. Instead of the attenuation hypothesis, those results may be supported by the additivity hypothesis of HSM which emphasizes the independent impact of systematic processing and heuristic processing on individuals’ judgment that perception of interactivity elicits systematic processing and belief/attitude serially, message interactivity in our study potentially represents a heuristic cue for prompting systematic processing rather than directly affect heuristic processing.