Negotiating environmental threats has been a key component of humans’ everyday life over evolutionary time. Evolutionary psychologists argue that millions of years of threat encounters have likely left their mark on the human mind (Barrett, 2005, 2015; Cosmides & Tooby, 1997). Consistent with this proposal, human infants differentially attend to and learn about ancestrally-recurrent threats such as dangerous animals and angry faces (Barrett & Broesch, 2012; LoBue, 2013). Little is known, however, about infants’ reactions to ancestrally recurrent dangers in broader naturalistic contexts. Although they may seem harmless, plants manufacture a variety of different defenses that can be dangerous to humans. Accordingly, infants are reluctant to touch benign-looking plants; a behavioral strategy that protects them from potential plant dangers (Wertz & Wynn, 2014a). This dissertation investigates several novel aspects of this behavioral avoidance strategy toward plant threats including infants’ responses to visible plant threats (i.e., thorns). The findings presented in Chapter 1 show that 8- to 18-month-old infants exhibit both an initial reluctance to touch and minimized subsequent physical contact with plants compared to other object types. Interestingly, infants treat all plants as potentially dangerous, whether or not the plants look benign or are covered in sharp-looking thorns. Chapter 2 demonstrates that infants continue to exhibit this behavioral avoidance strategy toward plants even when additional social cues are present. Surprisingly, however, infants do not respond differently to the plants or other stimulus objects in negative and positive social information conditions. Instead, they seem to react to the fact that the experimenter touched the objects. The eye-tracking study presented in Chapter 3 did not find evidence that the presence of pointy-shaped elements influence 8- to 10-month-old infants’ visual attention toward plants, novel artifacts, and familiar artifacts. Taken together, the findings of this thesis suggest that understanding the complexity of infants’ responses to threat in the natural world requires taking into account both the type of entity that infants are responding to (plants vs. non-plants) and the different aspects of social information provided by others (touch vs. emotional expression).
