Elsevier

Acta Psychologica

Volume 143, Issue 3, July 2013, Pages 284-291
Acta Psychologica

Spiders appear to move faster than non-threatening objects regardless of one's ability to block themā˜†

https://doi.org/10.1016/j.actpsy.2013.04.011Get rights and content

Highlights

  • ā€¢

    We examined perceived speed of spiders, ladybugs, and balls.

  • ā€¢

    Spiders were perceived to move faster than ladybugs and balls.

  • ā€¢

    Decreasing the perceiver's ability to block the object made the object look faster.

  • ā€¢

    Blocking ability and object type made independent contributions to speed perception.

Abstract

We examined whether perception of a threatening object ā€“ a spider ā€“ was more accurate than of a non-threatening object. An accurate perception could promote better survival than a biased perception. However, if biases encourage faster responses and more appropriate behaviors, then under the right circumstances, perceptual biases could promote better survival. We found that spiders appeared to be moving faster than balls and ladybugs. Furthermore, the perceiver's ability to act on the object also influenced perceived speed: the object looked faster when it was more difficult to block. Both effects ā€“ the threat of the object and the perceiver's blocking abilities ā€“ acted independently from each other. The results suggest effects of multiple types of affordances on perception of speed.

Introduction

An intuitively appealing idea is that perception should accurately represent the world as it is. Perception is the only source of information about the external world, and thus it stands to reason that a more accurate perception would be more adaptive. The system could handle some error due to noise and some systematic biases, yet one might expect (and hope) perception to be more resistant to these errors in critical situations. By critical situations, we mean situations that necessitate immediate, appropriate actions where behavioral errors could have important consequences. One example of a critical situation is the presence of a nearby threat. Thus, one hypothesis is that perception of a threatening object would be more accurate and resistant to perceptual biases.

Some existing research provides support for this hypothesis. Contrast sensitivity increases after viewing fearful faces (Phelps, Ling, & Carrasco, 2006). Although the fearful faces themselves are not threatening, they are indicative of threat nearby. After viewing a fearful face, participants were able to detect the orientation of sinusoidal gratings of lower contrasts than after viewing a neutral face. Thus, just as one might hope and expect, perception was more accurate in the presence of an indication of threat.

Another example of when perceptual sensitivity increases in the presence of a threat is derived from experiments with looming stimuli (Lin, Murray, & Boynton, 2009). Participants performed a challenging visual search task where they had to determine the orientation of an oval presented among circles. Prior to each search, a cue was presented. The cue was a circle that moved towards the observer and was either a looming target or a near miss. Had the circle continued on its trajectory, looming targets would have collided with the observer whereas near misses would pass by the observer without collision. The cue was either presented at the same location as the target or at the same location as a distractor. The target search was most efficient when the cue was a looming object and at the same location as the target. Looming objects pose a threat, and these results demonstrate that perception is more efficient to find target objects when they occur at the same location as the threat. In another experiment, visual search efficiency also increased after previously viewing a fearful face compared to a neutral or happy face (Becker, 2009).

A third example reveals a reduced bias in perceived size when the object contains an image with negative valence (van Ulzen, Semin, Oudejans, & Beek, 2008). Circles were presented with positive, neutral, or negative images superimposed on the circles. The perceived size of these circles was underestimated compared to a circle with no superimposed image. However, this bias to see the circles as smaller was reduced for circles with a negative image. These circles were still underestimated compared to blank circles but were not underestimated as much as circles with neutral or positive images.

While these studies suggest increased perceptual sensitivity and accuracy in the presence of a threat or a negative stimulus, there is also evidence that perception in fearful situations is less accurate and more prone to biases. This evidence (reviewed below) is consistent with the New Look approach to perception. According to this approach, perceivers see objects in terms of their need and value (Bruner, 1992). For example, coins worth more look bigger than coins that are worth less, and poorer children see coins as bigger (Bruner & Goodman, 1947). The New Look approach was discounted largely based on methodological issues and the use of ambiguous terms (Carter and Schooler, 1949, Gordon, 2004), but the studies reviewed below are consistent with and provide new evidence for the New Look approach to perception.

One perceptual bias that is exaggerated in the presence of a threat is apparent in the perception of hill slant. In non-threatening situations, hill slant is grossly overestimated (Proffitt, Bhalla, Gossweiler, & Midgett, 1995). In a fearful situation, perception of hill slant is even more overestimated than in a non-fearful situation (Stefanucci, Proffitt, Clore, & Parekh, 2008). Participants viewed a hill from on top while standing on a skateboard or on a wooden platform. None of the participants had skateboarding experience, so standing on a skateboard created a fearful situation. In this case, the participants perceived the hill to be even steeper than did participants who stood on the wooden platform.

Another bias is also apparent in perception of heights, which also tends to be exaggerated (Stefanucci & Proffitt, 2009). Vertical extents look farther than their actual extent. Moreover, when the vertical extent is viewed from on top of a balcony, the perceptual exaggeration of the extent increases relative to when the extent is viewed from on the ground below. The balcony poses the threat of falling with severe consequences. Again, according to the original hypothesis proposed earlier, one might expect perception to be more accurate and less prone to bias in such a critical situation. Instead, these perceptual biases were further exaggerated.

More recently, research demonstrated that fearful objects look bigger and closer than neutral or disgusting objects. Perceived size of a live spider was correlated with spider phobia ratings (Vasey et al., 2012). In non-phobic participants, similar biases are also apparent. In one study, a live spider was placed on a toy train track, and participants had to pull the spider closer, then estimate the distance to the spider. Participants with depleted psychosocial resources, and thus with less capacity to cope with a threat, estimated the distance to the spider as closer than did participants who estimated the distance to a cat toy (Harber, Yeung, & Iacovelli, 2011). In another study, a live spider was placed on a tabletop, and participants rated their fear of the spider and their disgust of the spider (Cole, Balcetis, & Dunning, 2013). Fear ratings negatively correlated with perceived distance to the spider. Those who rated the spider as more fearful than did others perceived the spider to be closer. In a second study, participants met a confederate then watched a video in which he described himself performing threatening behaviors, disgusting behaviors, or neutral behaviors. Afterwards, the participant and confederate reconvened, and the participant judged the distance to the confederate. Participants who viewed the video describing threatening behaviors judged the confederate to be closer than did participants who viewed the video describing disgusting or neutral behaviors. In other words, the confederate looked closer when he was seen as a threat than when he was seen as disgusting or neutral.

In the last set of studies, the authors argued that threat, but not disgust, influences perceived distance because threat calls for immediate action (or at least immediate preparation for action) and that seeing the threatening object as closer could promote faster preparation time for action (Cole et al., 2013). In the current experiments, we extend on these findings to examine if threat also influences perception of speed. We tested whether a threatening object looks to be moving faster than a neutral object. Just as seeing a threatening object as closer could promote faster preparation for action, seeing a threatening object as moving faster could also be adaptive in promoting faster action preparation.

The second aim of the current studies was to examine the relationship between two types of effects on perception: 1) the effects of threat on perception and 2) the effects of a person's ability to act on perception. The latter effects are known as action-specific effects on perception (Proffitt, 2006, Witt, 2011). For example, a softball player who is hitting better than others sees the ball as bigger (Gray, in press, Witt and Proffitt, 2005). Similarly, objects that are easier to block look to be moving slower (Witt and Sugovic, 2010, Witt and Sugovic, 2012). Dozens of studies have found effects of a variety of actions including walking, throwing, kicking, jumping, climbing, swimming, reaching, grasping, batting, hitting, putting, and shooting on perception1. Yet almost no research has examined the connection between ability-related effects and threat-related effects on perception.

These two types of effects could relate to each other in a number of ways. First, the two effects could operate independently from each other, and in an additive fashion. In this case, an object would look differently based on a person's ability to act on the object and also look differently based on the potential threat of the object. A result of separate, independent effects is predicted by claims that the two types of effects are driven by different anatomical mechanisms. Threat-based effects are thought to arise from processes in the amygdala (e.g. Phelps, 2006), whereas ability-based effects are thought to arise from premotor processes (Witt and Proffitt, 2008, Witt et al., 2012).

A second possibility is that threat could reduce or eliminate action-specific effects. In other words, a perceiver sees the world in terms of his or her ability to act but only in the absence of threat. In the presence of a threat, the world would be perceived in relation to the given threat and independently of the perceiver's ability to act. This idea has support from a previous experiment. Participants threw darts while standing on rock climbing footholds placed near the ground or several meters above ground. In the low height condition, dart throwing performance influenced perceived size of the target (CaƱal-Bruland, Pijpers, & Oudejans, 2010), replicating previous work (Wesp, Cichello, Gracia, & Davis, 2004). Participants who hit the target more successfully than others perceived the target to be bigger. However, dart throwing performance did not influence perceived size in the high height condition. In the high height condition, the threat of falling was present and salient, and in this condition, perception was not influenced by the person's ability to successfully throw the darts. This study found that biases in perception based on a person's ability to act were eliminated in the presence of a threat.

A third possible outcome is that action-specific effects might modulate the effect of threat on perception. Under conditions for which there is a low likelihood of performing an action successfully (i.e. low ability to act), threat might have a large influence on perception. For example, a spider might appear much faster if a person is not capable of successfully blocking the spider. In contrast, under conditions for which there is a high likelihood of performing an action successfully (i.e. high ability to act), threat might have little-to-no influence on perception. For example, a spider might not appear any faster than a neutral object if both are easy to block.

One previous study supports this possibility (Harber et al., 2011). Participants stood on a balcony and estimated the distance to the ground 5 stories beneath them. Critically, one group of participants was told to hold the handrail whereas another group had their hands tied behind their backs. As a result, the threat of falling was higher for the group with their hands tied than for the group holding the railing. In addition, participants' self-esteem was measured. Self-esteem is considered to be a psychosocial resource, and according to the authors' Resource and Perception Model, is interchangeable with physical support. Thus, one could argue that participants with high self-esteem therefore had higher ability to deal with the threat of falling, whereas participants with low self-esteem had lower ability to deal with the threat of falling. The results showed that self-esteem did not influence perception for participants in the hold-railing (less threat) condition, but self-esteem did influence perception for participants with their hands tied behind their back (more threat condition). In this condition, participants with lower self-esteem (i.e. less ability) perceived the height to be taller than did participants with higher self-esteem (i.e. higher ability) (Harber et al., 2011). The authors interpreted their results as showing that increased resources (in this case, psychosocial resources) modulate the effects of threat on perception. If we think of physical ability as a resource, then this would predict that the effects of ability on perception might be exaggerated in the presence of a threat.

In order to differentiate between these three possible outcomes, we examined the effect of a person's ability to block an object on perceived speed of the object (Witt and Sugovic, 2010, Witt and Sugovic, 2012) in the presence of a threat (a spider) or a neutral object (a ball). Participants attempted to block the object with various sized paddles, which made the blocking task easier or harder, and estimated the object's speed.

Section snippets

Method

Sixteen students participated in exchange for course credit. Each was seated in a room at a uniformly white table (2.44Ā m by 1.22Ā m) onto which stimuli were displayed from a downward-facing projector (see Fig.Ā 1). The projected area was 83Ā cm by 107Ā cm.

Participants first completed a training phase to familiarize them with the anchor speeds that they would later use to make speed judgments. During the first part of training, text indicated if the speed would be slow or fast. Then a white circle (4.7Ā 

Experiment 2

The purpose of this experiment was to replicate the findings from Experiment 1 using a different measure of speed perception. In this experiment, participants rated the speed of the object on a scale of 1 to 7. This measure has been used previously to demonstrate convergence across multiple types of speed judgments (Witt & Sugovic, 2012). Such convergence supports the idea that the effects occur in perception, rather than in the post-perceptual processes that generate a particular response (

Method

Fifty-four students participated in exchange for course credit. Everything was the same as in Experiment 1 except that participants judged the speed of a spider or of a ladybug. The ladybug was red with black spots and was the same size as the spider.

Results and discussion

Two participants in each condition had multiple mean speed ratings that were at least 1.5 times beyond the interquartile range, and were removed prior to the analyses. The remaining data were analyzed as before and are shown in Fig.Ā 4. Paddle size

Experiment 4

Another difference between the spider and the ball or the ladybug is the shape of the object. While there is no previous literature to suggest that object shape could account for our effects on perceived speed, we decided to test this directly.

General discussion

In the current experiments, participants blocked and estimated the speed of a spider (threatening, animate object), ball (neutral, inanimate object), or ladybug (non-threatening animate object). Several effects emerged. First, spiders looked to be moving faster than did non-threatening objects. Second, these studies replicate the effect of affordances on perception (e.g. Witt & Proffitt, 2005). In particular, objects that were easier to block appeared to be moving slower than objects that were

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    ā˜†

    This work was supported by a grant from the National Science Foundation (BCS-0957051) to JKW.

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