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Protective Behavioral Strategies

This research area examines whether infants possess behavioral strategies to avoid the type of harm that plants can cause. Plants produce a variety of different defenses to protect themselves from herbivores, including toxic chemical compounds and dangerous physical structures like thorns and stinging hairs. Therefore, the primary dangers plants pose to humans are poisoning and physical injury. However, a dangerous plant can only inflict serious damage if one approaches it and makes physical contact with it by, for example, grabbing it or consuming part of it. As a result, a simple behavioral strategy of minimizing physical contact with plants can be quite effective in minimizing exposure to plant dangers. Further, because fatally toxic plants can look quite delicate and beautiful, the best behavioral avoidance strategy is to minimize contact with any unknown plant, regardless of how it may look, until one has received additional information about it. Therefore, we predicted that infants would be reluctant to touch plants compared to other types of entities prior to receiving social information from adults. 
 

Protective Behavioral Strategies
© MPI fuer Bildungsforschung

 

THYME TO TOUCH
 

In the first study to test this proposal, we presented 8- to 18-month-old infants with a series of objects across two different experiments (Wertz & Wynn, 2014b). These objects were real plants, realistic-looking artificial plants, novel manmade artifacts, familiar manmade artifacts, and other naturally occurring entities. As predicted, infants took longer to reach out and touch plants, both real and artificial, compared to all of the other object types. Further analyses confirmed that this reluctance was specific to the plants in our stimulus set and not to more general features like colors, shapes, or scents. These results provided the first empirical evidence for a plant specific behavioral avoidance strategy in human infants. Without clear social information from adults, infants do indeed take longer to reach out and touch plants than other entities. This strategy minimizes infants’ physical contact with plants, protecting them from the types of dangers that plants can inflict.
 

EVERY ROSE HAS ITS THORN
 

Because even beautiful plants can be deadly poisonous, the behavioral avoidance strategy should be applied to all plants, regardless of how they look. However, some plants do have readily-observable threats. For example, unlike toxic chemical compounds, the presence of physical defenses like thorns is visibly detectable. This project examines whether infants’ behavioral avoidance strategies are influenced by the presence of visually detectable plant threats, specifically thorns. To do this, we present infants with plants, novel artifacts matched to features of the plants, and familiar artifacts. Half of the stimulus objects in each category have pointed thorn-like shapes, while the other half do not. Our first findings in this project showed that 8- to 18-month-old infants took longer to reach out and touch plants, whether or not they had thorns, compared to the other object types, replicating our initial finding. Further, after making initial contact with each object, infants spent less time touching plants compared to novel and familiar artifacts, and touched the thorny parts of plants less frequently than either the thorny or non-thorny parts of any of the other object types. These results suggest that, in addition to the initial delay to touch plants, infants’ behavioral avoidance strategy also includes minimizing their subsequent physical contact with plants. Ongoing studies in this project are investigating the effect of social information on infants’ reluctance to touch plants. 
 

THE SEEDS OF SOCIAL LEARNING
 

If the purpose of the behavioral avoidance strategy is to protect infants from making contact with a plant before they know whether it is safe or dangerous, then infants should actively seek out information from other people when they are confronted with plants. Critically, increased social information seeking should occur before infants make physical contact with a plant. Our first results in this project indicate that 8- to 18-month-old infants do indeed engage in more social information seeking for plants compared to all of the other object types we tested. Importantly, this increase in social referencing occurs before infants touch plants and only when the plants are presented within their reach, which is precisely what would be expected from a behavioral avoidance strategy that protects infants from plant dangers. Further, we again replicated the initial finding that infants take longer to reach out and touch plants, but the increase in social referencing behavior was not simply a consequence of this fact. Infants’ increased social information seeking for plants remained even when we controlled for the amount of time before infants touched each object.
This kind of increased social information seeking, operating as part of a behavioral avoidance strategy, puts infants in the best position to glean information from others before making contact with potentially dangerous plants and sets the stage for further social learning processes. 

Publication

Elsner, C., & Wertz, A.E. (in press). The seeds of social learning: Infants exhibit more social looking for plants than other object types. Cognition. doi: 10.1016/j.cognition.2018.09.016 

Włodarczyk, A., Elsner, C., Schmitterer, A. & Wertz, A.E. (2018). Every rose has its thorn: Infants’ behavioral responses to pointy shapes in naturalistic contexts. Evolution & Human Behavior, 39, 583-593. doi:10.1016/j.evolhumbehav.2018.06.001

Wertz, A. E., & Wynn, K. (2014). Thyme to touch: Infants possess strategies that protect them from dangers posed by plants. 
Cognition130, 44-49. doi:10.1016/j.cognition.2013.09.002