Abstract:

Despite the growing urgency of waste separation as environmental concern, the rates of contamination from unsorted waste remain high without the monitoring or feedback from volunteers. How can we facilitate collaboration between residents and volunteers? To address the dilemma of waste separation, the present study conducted three experiments and a qualitative interview based on the theories of competitive altruism and social influence to investigate the effects of familiarity and age on residents' cooperation, as well as the mediating roles of reputational concern and social distance.

Using scenarios, participants were asked to read the instructions (each representing one of the conditions), and then to predict the extent of probability that they would cooperate in each condition. Experiment 1 adopted a 3 (age group of volunteers: primary children/younger/older) × 3 (volunteer familiarity: high/low/unfamiliar) within-subjects design to examine the differences in the cooperation of young people (M = 20.16 ± 1.01 years) with volunteers in different conditions. Experiment 2 adopted a 2 (age group of participants: younger/older; between-subjects variable) × 3 (age group of volunteers: primary children/younger/older; within-subjects variable) × 3 (volunteer familiarity: high/low/unfamiliar; within-subjects variable) mixed design, to examine the age-related differences of the cooperation between younger people (M = 40.63 ± 7.60 years) and older people (M = 68.90 ± 4.97 years) with volunteers in different conditions. The findings of Experiment 1 were replicated. Experiment 3 adopted a 2 (age group of volunteers: younger/older) × 2 (volunteer familiarity: high/unfamiliar) within-subjects design to replicate the results of Experiment 1 and Experiment 2, and it lasted for four weeks at an interval of one week for each participant. Experiment 3 recruited 84 participants (M = 26.05 ± 11.01 years) and aimed to examine the mediating role of reputational concern and social distance in the relationship between familiarity and cooperation.

Experiment 1 showed that participants cooperated more with the high familiar volunteers (79.11%) than with the low familiar (61.60%) or strange volunteers (27.64%). The higher the familiarity, the greater the cooperative intention (see Figure 1), χ²(16, N= 1422) = 285.64, p< 0.001. As age and familiarity interact to affect the cooperative intention, participants cooperated more with older volunteers (88.98%) than with primary children (77.12%) in the low familiar condition, χ²(1, N= 236) = 5.90, p = 0.015, odds ratio = 2.40, 95% CI [1.17, 4.92].

Experiment 2 replicated the results of Experiment 1 (see Figure 2), and found that familiarity had a significant effect on the cooperative intention of both younger and older adults [current: F(2, 344) = 128.04, p < 0.001, η² = 0.43; next time: F(2, 344) = 99.05, p < 0.001, η² = 0.37]. As age and familiarity interact to affect the cooperative intention, F(4, 688) = 3.12, p = 0.015, η² = 0.02, participants cooperated more with older volunteers (M = 5.36, SD = 1.15) than with primary children (M = 5.14, SD =1.37) in the low familiar condition. Besides, older adults cooperated more with older volunteers (M = 5.54, SD = 0.11) than younger adults (M = 5.20, SD = 0.11), p = 0.025, while less with strangers (M = 4.28, SD = 0.13) than younger adults (M= 4.77, SD = 0.13), p = 0.008.

Experiment 3 replicated the results of the first two experiments, and examined the underlying mechanism (see Figure 3). A bootstrap analysis (bootstrap resamples = 5,000) revealed that the bias-corrected 95% CI of both social distance [−0.027, 0.090] and reputational concern [−0.020, 0.030] did not exclude zero, indicating that the indirect effects of social distance (β = 0.031, SE = 0.030) and reputational concern (β = 0.004, SE = 0.013) were not significant. Moreover, when social distance and reputational concern were simultaneously treated as mediators in the multiple mediation model, the indirect effect of social distance and reputational concern (β = 0.034, 95% CI [0.019, 0.053]) was significant. These findings indicated that social distance and reputational concern play a serial mediating role in the effect of familiarity on cooperation. The results of multiple regression analysis and qualitative interviews showed that the monitoring and feedback from volunteers, familiarity with the residents, and individual prosociality, play key roles in promoting waste separation.

These findings provide suggestions and scientific support for the practice of waste separation and saving management costs. The present study demonstrates that helping residents to become familiar with volunteers in advance, or recruiting people who are familiar with residents as volunteers, could promote waste separation. These strategies can promote the cooperative intention of residents, and help them form the habit of waste separation. Social distance and reputational concern play a serial mediating role in the effect of familiarity on cooperation.

Key words: familiarity, age differences, reputational concern, social distance, cooperation