Perky effect
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Perky effect
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*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
The Perky Effect describes the relationship between real visual information (perception) and mental imagery. Discovered by C. W. Perky in 1910, her experiments were able to show that visualization of images can depress the sensitivity of perception of real visual targets. In her study, participants were asked to imagine certain objects on a white screen, such as a fruit, a tree, or a book. After a few trials, a faint, real image was projected on the screen of the subject matter. Participants were quite often unable to distinguish between their imagined projections and the true images. For example, one participant was surprised that the banana appeared to be in a different orientation than the one they were attempting to imagine it in. Another maintained that the title of the book they were imagining was legible, while there was no title in the actual, projected image. The Perky effect has since been updated to describe the reduction in visual performance due to the maintenance of mental imagery.
A research group was interested in both replicating Perky’s findings and in investigating the influence of contrast on this effect. Before the experiment, researchers asked some participants to imagine lines on a white board and choose a color chip (from a prepared set between black and light grey) that matched most closely with the color of their imagined lines. These lines were called “fixation lines.” Other participants were given a specific color of either black or grey fixation lines (displayed on the white target), while the control group had no fixation lines. The imagined/real color of the fixation line was referred to as the participant’s “mask.”
During the task, each participant received a picture showing an image of two black circles. The picture was removed from view and a target with two black lines was shown, one originating from each previous fixation point with a half-inch gap between the lines.
Figure 1. An image displaying both the black circles and black lines “On,” “Close,” and “Far” from the imaginary/real lines. These fixation lines are shown as they appear in the grey condition, as dashed lines in the figure.
For the imagined condition, the participant was asked to imagine the previous image ‘ON’ the two fixation lines (nearest line 0.1 cm), ‘CLOSE’ to the fixation lines (nearest line 0.8 cm]), or ‘FAR’ from the fixation lines (nearest line 2 cm). For the black and grey line conditions, the four fixation lines were shown continuously and the black circles were removed and replaced with black lines. The task was to decide whether fixation lines were offset either to the left or to the right. The results are shown in Figure 2.
Figure 2: The mean percent of correct responses for each condition over all participants was calculated. The duration of each trial was between 3 ms and 25 ms. The baseline condition (‘None’) was practiced until the participant was at least 90 % accurate. The effect of distance, line type, and the interaction between distance and line type were all significant at p < 0.001.
Reeves, A., & Craver-Lemley, C. (2012). Unmasking the Perky Effect: Spatial Extent of Image Interference on Visual Acuity. Frontiers in Psychology, 3, 296. doi:10.3389/fpsyg.2012.00296
Thomas, N. (2014). The Perky Experiment. Stanford Encyclopedia of Philosophy.
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[question] => Which conclusion can correctly be drawn regarding the results displayed in Figure 1
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[answer] => 1
[description] => Reason for the Correct Answer:
The effects of line type and proximity to the fixation lines was significant.
The Perky effect describes a significant reduction in acuity in imagined lines and black lines conditions.
The Perky effect was shown to increase with proximity for the imagined masking lines, the grey masking lines, and the black masking lines.
A clear Perky effect was shown, with an increasing effect when the masking lines were visualized closer in proximity to the fixation lines.
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[each_answer] => A. A clear Perky effect was shown, with an increasing effect when the masking lines were visualized closer in proximity to the fixation lines.
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[each_answer] => B. No Perky effect is shown in the data.
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[each_answer] => C. It is not possible to infer whether the data show a Perky effect.
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[each_answer] => D. A slight Perky effect was shown, with a decreasing effect when the masking lines were visualized closer in proximity to the fixation lines.
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => What part of the visual system is the Perky effect likely taking place?
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[answer] => 1
[description] => Reason for the Correct Answer:
A problem with fixation would make it difficult for the participants to complete the control (‘None’ masking condition) accurately. In this condition, participants averaged over 90% accuracy.
The Perky effect is a perceptual phenomenon; however, the eye is not transmitting imagined images to the brain.
The Perky effect likely takes place in the brain itself.
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[each_answer] => A. In the brain.
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[each_answer] => B. In the retina.
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[each_answer] => C. The Perky effect does not happen in the visual system. It is a fixation problem.
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[each_answer] => D. In the fovea.
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => What is a masking stimulus?
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[answer] => 3
[description] => Reason for the Correct Answer:
A masking stimulus causes a failure in the first stimulus.
Interference happens when two stimuli are perceived simultaneously.
A masking stimulus is shown immediately after a first visual stimulus, which causes a failure to perceive the first stimulus.
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[0] => Array
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[each_answer] => A. A masking stimulus is shown seconds after another stimulus, which causes an enhancement in the perception of the first stimulus.
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[each_answer] => B. A masking stimulus is shown simultaneously to another stimulus, which causes a failure to perceive the first stimulus.
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[each_answer] => C. A masking stimulus is shown immediately after a first visual stimulus, which causes a failure to perceive the first stimulus.
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[each_answer] => D. A masking stimulus is shown immediately before a first visual stimulus, which causes an enhancement in the perception of the first stimulus.
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[quiz_unique_key] => 2261298308
[question] => Another researcher shows that the Perky effect lasts for as many as six seconds. How might this finding affect the results shown in Figure 1?
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[answer] => 1
[description] => Reason for the Correct Answer:
The duration of the trials represented in Figure 1 were between 3 ms and 25 ms.
The trial times were determined by the participant.
It is not possible to infer that the results are different from those described in Figure 1 other than that both support the existence of a Perky effect.
The new findings will not affect the findings of the study described in Figure 1.
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[each_answer] => A. The new findings will not affect the findings of the study described in Figure 1.
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[each_answer] => B. The new findings strengthen the results described in Figure 1.
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[each_answer] => C. The impact of the Perky effect will be decreased with a longer trial.
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[each_answer] => D. The new findings contradict the results in Figure 1.
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[quiz_unique_key] => 574431310
[question] => What Gestalt principle describes the integration of perception and mental imagery manifested in the individual who described the book they were imagining?
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[answer] => 1
[description] => Reason for the Correct Answer:
Law of similarity claims that elements that are similar tend to be grouped together.
Law of continuity describes the ability to group units into lines following the smoothest path.
Law of proximity claims that elements viewed as groups if those elements are close together.
Law of pragnanz describes the principle that elements are grouped together if they seem to be a part of a pattern, which is coherent or unified. An imagined title appearing on a book follows such a pattern.
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[each_answer] => A. Law of pragnanz
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[each_answer] => B. Law of continuity
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[each_answer] => C. Law of similarity
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[each_answer] => D. Law of proximity
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