A Bias for the Tops of Objects and Bottoms of Scenes

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Vision researchers have long been interested in describing the biases we have when we look at the world. Early research into the visual system identified something called an “upper hemifield bias” where we tend to pay more attention to and be more affected by things that are in our upper visual field. This is a type of verticality bias. There are also horizontal biases that arise, in part, as a function of the way we read and write. In cultures where language is written from left to right, people have a bias to perceive more to the right than to the left of wherever they’re looking. This helps us when reading by being able to predict what word is coming up next.

In a new research study published in the Journal of Experimental Psychology: Human Perception and Performance, and presented recently at the meeting of the Psychonomic Society, Matthew Langley and Michael McBeath described how the verticality bias depends on the content of what we are looking at. They found that when people look at objects (things that are graspable and/or in our immediate environment), they attend more to their top parts. But when they look at scenes (for example, a picture of a beach or a forest), they attend more to the bottom parts.

How Are These Biases Tested?

In a clever paradigm, the researchers presented participants with three objects, or three scenes, side by side. In each case, the middle item contained a blend of elements from the item on the left and the item on the right. For example, the middle item could share the same top part as the right item and the same bottom part as the left item (see the figure below).

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Which side item (A or C) looks more like the middle item (B)?

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Participants were asked to select which of the side items (A or C) was more similar to the middle item (B). In most cases, people chose the item that matched the top part.

However, when the items depicted scenes rather than object-like shapes, the bias was reversed: people tended to select the items that matched in their bottom parts.

An Ecological Bias

The authors suggest that the reason for these perceptual biases has to do with the affordances with which we interact with the world. When we interact with objects, we tend to see them from above (a top-view vantage point) and we are more likely to grasp their top parts. In contrast, we tend to interact with scenes by navigating through them. When we are walking through a forest, we need to pay attention to the ground to make sure we don’t stumble or step into a hole.

Even though participants in the study were not really interacting with the objects or scenes (they were just looking at pictures), the biases we develop through our experiences with objects and scenes in the real world appears to translate to the lab setting. In fact, the more realistic the objects and scenes tested, the more pronounced these biases were. In a followup study recently published in Developmental Psychology, the authors show that these biases exist in children as well.

The bias for attending to the top of objects may be part of the reason we tend to look at the upper eye of tilted faces. Rather than the upper eye providing more information than the lower eye, this tendency may simply be derived from an overall bias to look at the tops of objects (and the bottoms of scenes).

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