Unlike social judgments, perceptual judgments are anchored in concrete reality and should not depend on social context. However, in recent research, even perceptions of physical space turn out to depend on the social and emotional context. In particular, ecological approaches suggest that perception may depend on contextual factors not previously considered. For example, research shows that hills seem steeper to a person wearing a heavy backpack. Contextual factors influence perception because they are relevant to actions: A hill is harder to climb for an encumbered person, and thus, appears as steeper.
We showed that after having consumed glucose people find a hill less steep than after having consumed noncaloric sweetener, presumably because glucose provides energy (Schnall, Zadra & Proffitt, 2010). In addition to such physiological influences, similar effects are obtained with respect to a psychosocial resource, namely social support. In the presence of a friend, or even when simply thinking about a significant other, people perceive a hill to be less steep than when they are alone (Schnall, Harber, Stefanucci & Proffitt, 2008).
Some of our work demonstrates that resources considerations are also relevant when it comes to social power: Indeed, the definition of having power is having control over one’s own and other people’s resources. We showed that people who feel powerful literally experience a heavy burden to be less heavy than people who feel powerless (Lee & Schnall, 2014). Thus, whether or not you have resources available changes how you see the physical world.
In addition to the availability of resources, motivational orientations involving approach and avoidance also play a role. People who stand in front of a steep hill while the notion of approach is activated find the hill to be more steep than people from whom avoidance is activated, but only if they are in good physical shape and action is therefore feasible (Krpan & Schnall, 2014a). The effect, however, goes away when approach cues are invalidated by telling participants explicitly that climbing the hill will not be necessary. Thus, embodied cues relating to approach are only effective as long as they provide meaningful input regarding an impending action.
In the context of distance estimates we find that approach and avoidance have different effects depending on whether they occur in response to positive or negative stimuli (Krpan & Schnall, 2014b). More specifically, we find that when there is a mismatch between the two, namely when people engage in response toward negative stimuli, or or avoidance towards positive stimuli, they perceive the distance as closer than when there is a match. We interpret this to involve an attempt to resolve inconsisteny because participants in the mismatched conditions also show higher behavioral activation, and show more effort toward an irrelevant activity. Overall, this suggests when there is a problem that needs to be resolved, perception brings the object of conflict closer to the self.
The theoretical perspective that our work is built on, namely accounts of embodied and motivated perception, assumes that perception serves to guide behaviour: For example, when my body is full of energy it is easy to climb up a hill, whereas this is not the case when I am encumbered by a heavy backpack. Thus, perception is action-relevant. Most recently we showed that perception indeed allows predictions about the behaviours that a person will engage in (Krpan & Schnall, 2017). We asked participants to make distance estimates to a bowl of M&Ms, and then measured how much they ate subsequently. When the impulsive system was active (i.e., when participants were tired), distance estimates predicted eating, such that the farther away the M&Ms looked, the more participants ate. We also showed that if participants were instead alert and in an reflective state of mind, they went with behaviour intentions linked to food restraint.
In general there is ample evidence that people see the world as a function of their current bodily states, and this has consequences for action. In other words, perception provides a read-out of the things one can, or cannot do in a given environment. However, such bodily or contextual influences that drive perception are only effective as long as participants operate in a relatively automatic manner; once they become aware of potential influences on perception, they discount them, as is the case for many other judgment processes (Schnall, 2017a). One important implication of this work is that it may not be possible to maintain a functional distinction between perception and judgment, because in the complex interplay relating to action various processes are closely intertwined (Schnall, 2017b).
Cambridge Body, Mind and Behaviour 