倒面效应
English
Diviser
Vue d'ensemble
资料来源： 实验室的乔纳森 Flombaum — — 约翰 · 霍普金斯大学
感知，在通常的情况是，能够认识和解释复杂的刺激就会感到轻松但实际需求复杂密集处理。这是因为处理是专门和自动化对某些类型的非常重要的刺激。这种现象的最佳范例是面孔加工。人们不尝试检测和识别人脸。似乎只是发生。然而，检测的面孔，并告诉他们彼此是实际上要求苛刻的计算任务。
人类的面部识别能力依赖于专门的计算和专用的大脑网络。一个简单的演示，这是倒面效应。认识到颠倒的面孔是比认识到他们右侧起来，难但也不是如此对于许多其他类型的视觉对象。在以各种方式，证明了倒脸效应。该视频演示附带编码记忆范式为调查面部处理和倒面效应。
Procédure
Résultats
To analyze the results, simply compute the proportion of faces correctly identified by the participant in trials with upside-down (inverted) and trials with right-side up (upright) faces. Compare performance using a bar graph, as shown in Figure 2. For most visually normal observers, accuracy will be much higher with upright compared to inverted faces. However, this is a difficult task, and you may find performance below 0.9 even for upright faces. For inverted faces, performance may even approach chance, 0.5-what an observer would score if they just guessed on each trial. Poor performance with inverted faces shows that specialized computations and brain mechanisms used for recognizing faces are tuned to take advantage of the fact that faces are almost always experienced in an upright orientation.
Figure 2 Memory accuracy for inverted compared to upright faces. Most visual-normal observers show considerably better performance recalling previously seen faces when shown upright, as opposed to inverted. Indeed, with inverted faces, performance can be close to chance (0.5) in a task like this. Poor performance with inverted faces is the inverted-face effect.
Applications and Summary
The discovery that inverted faces are difficult to process has many applications. Neuroimaging studies, for example, have taken advantage of the effect to identify brain regions involved in specialized face processing. Brain scans are taken when observers view upright as well as inverted faces. The responses to the two kinds of stimuli are then compared. Both sets of stimuli have very similar visual properties overall, leading to similar activity throughout much of the visual system. In one brain area though, upright faces produce a much more vigorous response than inverted ones, suggesting that inverted faces fail to engage specialized face-processing neurons. The area that responds this way is called the fusiform gyrus, or the fusiform face area (sometimes FFA for short). This brain region is implicated in many other studies that investigate specialized aspects of face processing.
A second application has to do with a disorder known as prosopagnosia. This refers to extreme difficulty recognizing, at times even detecting faces. Prosopagnosia can arise following brain damage to the fusiform gyrus. But it is now known to also appear in people with no known cause of brain damage. One way that prosopagnosia is assessed involves the inverted-face effect. In particular, individuals with prosopagnosia don't show a typical inversion effect. Although they have no more trouble recognizing upside down faces than they do right side up ones, they have considerable trouble with right side up ones in general. This lack of an inverted face effect suggests that prosopagnosia is caused by the absence of specialized face processing systems-the kind that seem to know that faces are usually seen right side up.
Transcription
We don’t try to detect and recognize faces—it just happens, incidentally.
Impressively, for successful recognition, complex and demanding computations must occur in dedicated brain networks to integrate separate features into a cohesive face.
While recognizing faces right side up is relatively easy, identifying them in an upside-down position is far more difficult, even though this is not true for other kinds of visual objects.
This is often referred to as the inverted-face effect, and is used in experiments designed to investigate how face recognition takes place both cognitively and in the brain.
This video will demonstrate how to design and execute, as well as how to analyze and interpret an experiment investigating the inverted-face effect via an incidental-encoding memory paradigm.
In this experiment, participants are asked to judge male and female faces in two difference phases: incidental exposure and testing.
During the first incidental-exposure part, the participant is shown a set of 40 faces, one-at-a-time for 1 s each.
After every image is displayed, the participant is asked to report whether it was male or female by making an associated key press. This process mimics our natural ability to process faces—incidentally, without knowing it.
Then, for the second, test phase, the participant is shown two faces side-by-side. One is randomly chosen from the incidental-exposure portion and the other, called the foil, is sex-matched and never seen before by the participant.
Faces in the testing period are also randomly intermixed, with half of them upside-down and the other half, right side up. The participant is asked to indicate which of the two was seen previously.
In this case, the dependent variable is the number of faces correctly identified—a simple measure of memory accuracy—across upright and inverted orientations.
Participants are expected to perform better at recalling previously seen faces when they are shown upright, as opposed to inverted. Poor performance when identifying the inverted faces is known as the inverted-face effect.
Before starting the experiment, verify that the participant does not have any known visual impairments or difficulty in recognizing people.
To begin, seat the participant 60 cm from the presentation computer. Explain the instructions for the incidental-exposure phase without mentioning the test phase to come.
Start the program and stand nearby as the participant performs the first phase of the experiment and completes 40 trials in a 5-min period. Note that they see a single face for 1 s, and identify the sex of the face by pressing the ‘M’ key for male or ‘F’ for female.
Following the initial phase, thank the participant for completing this portion of the study and inform them of the instructions for the next test phase.
Once again, start the program and stand nearby as they complete the second memory phase of 40 trials. In this part, note that the participant presses either the left or right arrow key to indicate which face was observed previously.
To analyze the data, simply calculate the proportion of faces correctly identified and graph the results of memory accuracy by trial type: upright versus inverted.
Notice that for most visually normal participants, the accuracy is much higher when identifying faces that are upright as opposed to inverted, demonstrating the inverted-face effect.
Poor performance with the inverted ones—near chance—suggests that specialized facial processing mechanisms are tuned to take advantage of the fact that they are almost always experienced in an upright orientation.
Now that you are familiar with the complexity involved in processing inverted faces, let’s examine additional research scenarios where the effect can be applied.
Neuroimaging studies have used the inverted face effect to identify brain regions involved in specialized face processing.
Upright faces produce a stronger neural response in the fusiform face area, or FFA, than inverted ones, suggesting that inverted faces fail to engage specialized face-processing neurons.
In addition, brain damage to the FFA may result in a disorder known as prosopagnosia—the inability to recognize faces, including your own.
The task is often used to diagnose face blindness, as prosopagnostic individuals typically have just as much difficulty identifying right-side-up faces, as they do with those that are inverted.
You’ve just watched JoVE’s introduction to the inverted face effect. Now you should have a good understanding of how to design and conduct this type of experiment by implementing the encoding of a series of faces and retrieving familiar faces by memory. You should also know how to analyze and interpret the results.
Thanks for watching!