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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
The Distinction of Brain Processes Involved in Facial Recognition and
Object Perception
Jake Pedder (910488)
Melbourne School of Psychological Sciences, University of Melbourne
PSYC30018 : Neuroscience and the Mind
Jesse Shapiro
April 20th, 2020
Word count - 1579
Jake Pedder (910488)
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
The Distinctions of Brain Processes Involved in Facial Recognition and Object
Perception
There has been extensive debate and research into the brain mechanisms responsible
for facial processing and if these mechanisms are unique, domain-specific areas or whether
they are just a part of a domain-general object recognition function spread throughout the
brain. Currently, the investigation into this area of study continues, with a considerable
amount of papers published with alternative viewpoints, yet it is still not properly established
if one specific area of the brain is responsible for facial processing or if several individual
areas assist in the process. It was suggested in earlier studies that due to multiple different
types of effects that facial processing was part of a separate mechanism in the brain to other
object processing. Yin (1969) studied what was known as the inversion effect, whereby
participants found it much easier to identify upside down non-face objects with their
counterpart upright image, in contrast, they found it much more difficult to identify upsidedown faces compared to their upright position. Additionally, the composite effect which
works by splitting the face image horizontally (across the nose) and sticking it together with a
different person’s bottom half. Participants found it much easier to identify the top half
individual when the image was misaligned with the bottom half compared to when the halves
are fitted smoothly. This suggests faces undergo a holistic form of processing, again making
them different to the way object images are processed (Young et al., 1987). It was widely
accepted that because of the fact faces are uniquely susceptible to these effects, they must
have a unique area of the brain for processing. However, Diamond & Carey (1986) found an
alternative hypothesis for these previous results. They brought in participants from the
general public and “dog breed experts” and found the inversion effect for images of dogs in
the “dog experts” group and not in the control group. This gave way to the expertise
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
hypothesis, which suggests that facial processing is not unique, as the mechanisms involved
are also engaged by objects (with in class-similarity) in which people have become experts
in. To attempt to resolve the debate Gauthier & Tarr (1997) developed Greebles, which they
aimed to be face-like objects. The greebles were split into 2 genders and 5 families, identified
by three differences in 3 features likened to a face (eyes, nose & mouth). Due to these
features, Greebles were considered face-like objects and were therefore considered to be
processed holistically like faces. The participants were then trained a group to become a
“Greeble expert”, with approximately 3240 trails to achieve this status. These “Greeble
experts” then showed faster and more accurate responses to greeble identification and a more
prominent inversion effect, suggesting mechanisms in the brain for the processing of faces is
not unique, with expertise training on face-like objects, similar results can be produce. This
was a widely accepted viewpoint in research over many years, however it is made on one key
basis, that Greebles accurately represent faces and therefore they process holistically.
Currently, new findings, theories and case studies have brought to light enough evidence to
dispute this assumption of Greebles accurately representing faces and indicates that Greebles
use brain mechanisms responsible for object-processing rather than facial recognition.
Firstly, it is important to consider the extensive findings of the scientific fMRI study
on the fusiform face area (FFA) made in numerous experiments. The knowledge of the FFA
has expanded over the recent years and is now known to play a key role in facial perception
when identifying a person’s mood, age, sex and other important factors in usually a splitsecond timeframe. Advances in the field began in the 1990’s, with fusiform areas responding
more greatly to faces over everyday objects, houses, letter strings and flowers (Kanwisher et
al., 1997; McCarthy et al., 1997; Puce at al., 1996). There is 3 specific pieces of evidence that
suggest the FFA responds to faces specifically and not other objects. The FFA responds to all
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
kinds of facial stimuli at different levels of intensity for example drawings of faces (Spiridon
& Kanwisher, 2002) and two-toned “Mooney faces” (Kanwisher et al., 1998), will still cause
activation of the FFA on the fMRI. Secondly, the activation of the FFA is nearly double when
shown an upright facial image to when shown an inverted facial image (Kanwisher et al.
1998). Lastly, for stimuli in which a face is presented to one of the participants eyes and nonface is presented to the other eye, the FFA has a higher response when the participants
perceives a face over when they do not even though retinal stimulation is unchanged (Tong et
al., 1998; Pasley et al., 2004; Williams et al. 2004).
Additionally, it is key to understand the neuropsychological basis for that indicates
the separation of these mechanisms. Farah’s (1990) study which reviewed all cases of visual
agnosia proposed two independent recognition systems, a holistic processing system
(associated with face recognition), and a structural processing system (associated with object
recognition). This fits with the evidence of a double dissociation system, whereby people
with different types of visual agnosia can have different symptoms. Importantly, a person
with prosopagnosia shows impairment in recognising familiar faces that they have seen
before yet show no impairment of recognizing objects (occurs usually with damage to
fusiform gyrus). Juxtaposed to this, there exists object agnosics like the induvial termed CK,
a man whose friends and family wondered after a closed-head injury why CK lost all interest
in his toy soldier collection? This led to tests being conducted on CK which consisted of,
inversion effects of faces, recognizing cartoon faces and perceiving faces made up of
individual objects (Moscovitch, et al., 1997). The results found that CK had normal intact
facial recognition and was always able to distinguish the faces in images presented but was
usually unaware that they were made up of different objects or not. This led the
experimenters to propose two separate mechanisms responsible for image processing, a
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
holistic, face-specific system (intact for CK) and a part-based object-recognition system
(damaged for CK), this supported the findings of Farahs’s (1990) study (Moscovitch, et al.,
1997). Similarly, a case study of a man named Edward who had a life of difficulties not
recognizing faces, suffered no serious head trauma and scored normally on vision tests while
also being very intelligent (PhD in physics) struggled to recognize familiar faces. Edward
was a prosopagnosic, however he could recognise Greebles. He was in the normal range for
speed, accuracy and additionally Edward was fully trained using the Gauthier et al. (1999)
rapid expertise method from their study and was able to become an expert in Greeble
identification (Duchaine et al., 2004). Edward and his abilities directly contradict the findings
of Gauthier et al. (1999) and their expertise hypothesis, due to the fact that Edward could
become an expert in greebles, while still being prosopagnosic, this implicates that Greebles
are not processed with the same mechanisms as faces. Case studies like this are very
important for the understanding of the brain and the mechanisms that work in tangent, yet
with all the expansive number of case studies of prosopagnosia, not one person shows
impairment of facial recognition and areas of expertise, yet the expertise hypothesis implies
these processes use the same area of the brain (McKone et al., 2007).
This leads us to discuss are Greebles face-like objects processed in the FFA under the
same mechanisms as faces if we become “Greeble experts”? Gauthier et al. (1999) reported
an activation in the FFA region which increased with Greeble training to become an expert,
and thus supported their expert hypothesis indicating that areas in the brain for processing
faces are not unique, yet this simply does not fit the findings of the previous case studies,
experiments and fMRI findings mentioned. So, what explains the findings of Gauthier et al’s.
(1999) study? This can be explained by more detailed, recent research conducted by
Kanwisher et al. (2006), who interpreted Gauthier et al’s. (1999) data much differently.
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
Noting that Gauthier et al. (1999) defined the FFA as a large square ROI over a centimetre on
a side, Kanwisher et al. (2006) guarantees the inclusion of voxels with these parameters in the
fMRI measure, which would unintentionally be skewing the data gathered by the fMRI. This
then suggest the data collected by Gauthier et al. (1999) from what they believed to be the
FFA may be really arising from the neighbouring fusiform body area (FBA; Peelen &
Downing 2005).
Conclusion
While it might not be set in stone if faces are special and have their own unique part
of the brain for processing, the recent findings in key studies certainly seem to be favouring
the direction of a domain-specific mechanism for facial-processing. Improved accuracy and
increased use of fMRI machines to scan and evaluate the FFA while processing objects and
faces have been essential in this shift in direction. The neuropsychological case studies of
agnosics and prosopagnposics also have played a key role in the development of a double
dissociative framework which indicates the separation of brain areas. Additionally, the
counter-research into the expertise hypothesis which creates questionability of the accuracy
in previous findings. The points all demonstrate different areas in the brain for processing
objects like Greebles and human faces. Future research could expand on the unique case
studies, aim to find more people who are visually agnosic and prosopagnosic to develop a
more consistent understanding of the areas of the brain that are damaged.
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
References
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Different Psychological Mechanisms Responsible for Facial Perception and Object Perception
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