Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2019 The non-specificity of prosopagnosia: Can prosopagnosics distinguish sheep? Alexander Robert Toftness Iowa State University Follow this and additional works at: https://lib.edu/etd Part of the Cognitive Psychology Commons, and the Neuroscience and Neurobiology Commons Recommended Citation Toftness, Alexander Robert, "The non-specificity of prosopagnosia: Can prosopagnosics distinguish sheep?" (2019). Graduate Theses and Dissertations.edu/etd/17109 This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact digirep@iastate.
The non-specificity of prosopagnosia: Can prosopagnosics distinguish sheep? by Alexander R. Toftness A thesis submitted to the graduate faculty in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Major: Psychology Program of Study Committee: Eric E. Cooper, Major Professor Christian A. Kelly The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis.
The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2019 Copyright © Alexander R. All rights reserved. ii TABLE OF CONTENTS Page LIST OF FIGURES.
iii LIST OF TABLES. 1 The Coordinate Relations Hypothesis. 3 Alternatives to the Coordinate Relations Hypothesis. 14 The Present Experiments.
20 Test of prosopagnosia. 20 Nature of the acquired prosopagnosia. 20 Age-matched and gender- matched control. 21 Design and Procedure.
32 Design and Procedure. INSTITUTIONAL REVIEW BOARD APPROVAL. 57 iii LIST OF FIGURES Page Figure 1 The Coordinate Relations Hypothesis. 5 Figure 2 Reference Points in the Coordinate Relations Hypothesis.
6 Figure 3 Experiment 1 Legislator Face Stimuli. 23 Figure 4 Experiment 1 Overall Results. 26 Figure 5 Experiment 1 Trial Level Results. 27 Figure 6 Experiment 2 Sheep Face Stimuli.
33 Figure 7 Experiment 2 Sheep Bodies Exemplars. 34 Figure 8 Experiment 2 Overall Results. 37 Figure 9 Experiment 2 Trial Level Results. 38 Figure 10 Experiment 2 Trials by Body Parts Results.
39 iv LIST OF TABLES Page Table 1 Accuracy in Experiment 1 by Trial Type and Correct Response. 28 Table 2 Accuracy in Experiment 2 by Trial Type and Correct Response. 40 v ACKNOWLEDGMENTS I would like to thank my committee chair, Dr. Eric Cooper, and my committee members, Dr.
Chris Meissner, and Dr. I would like to thank the Iowa State Sheep Teaching Farm for allowing the photographing of their animals during materials creation. I would also like to thank Charles “Joey” Peasley and Dr. Eric Cooper for their roles in the creation of the sheep photo stimuli.
Thank you to the age-matched control who agreed to participate in this project. Many thanks to my partner, family, and friends for their support over the years. Finally, a special thank you to LB, the prosopagnosic participant in these experiments, without whom this project would not have been possible. vi ABSTRACT The impact that prosopagnosia (face-blindness) has on the human visual system has long been hypothesized with regard to the specifics of the impairment.
The leading hypothesis in the literature, the face-specificity hypothesis, proposes that prosopagnosia is specific only to human faces. Other hypotheses have offered alternative explanations for what sorts of identification tasks might be affected by damage to the fusiform face area resulting in prosopagnosia, including the biological recognition, expert recognition, and subordinate-level recognition hypotheses. An additional hypothesis, the coordinate relations hypothesis, offers a compelling explanation for the underlying process disrupted by prosopagnosia: that the brain’s ability to detect metric changes has been damaged resulting in a deficit to face recognition. This hypothesis was tested by looking for deficits in performance in a prosopagnosic when identifying non-faces, because such differences would not be explained by the face-specificity hypothesis.
Therefore, sheep faces were used as a class of stimuli to explore whether prosopagnosia affects identification of sheep faces in much the same way that it affects identification of human faces. Results of two experiments showed that a prosopagnosic was impaired on identification of sheep faces, providing support for the coordinate relations hypothesis. INTRODUCTION As we continue to learn about the hardware of the brain that makes cognition possible, the non-specificity of brain functions is increasingly revealed. While brain functions can certainly be localized to an extent, the brain is not neatly divided into modular sections that specialize in one function and one function only.
We are now in an age of neuroplasticity and the connectome where it is increasingly difficult to label any part of the brain with a specific function because of the interconnectedness of processes. Instead, complex networks, varying not only between individual humans, but also across the entire lifespan of those humans, are now implicated in multiple tasks as opposed to one specific task. A veritable bevy of imaging techniques (e.) have revealed that the cerebellum, once known only for motor control, is involved in a wide variety of neurological functions (Schmahmann, 2016), that the amygdala, once known only as an emotional center, is important for memory, learning, pain, motivation, and other deeply interconnected processes (Amunts et al., 2005; Richardson, 1973), and even the very concept of morality, once thought to be housed in some vessel of the soul, is not a localized area whatsoever, but arises from multiple processes in distributed locations (Greene, 2015). But there are a few regions of the brain that have dedicated advocates insisting upon specific assigned functions.
Chiefly among these is the fusiform face area (FFA) and its neighboring regions implicated in the processing of human faces (e., Schalk et al., 2017; Kanwisher, 2017, Kanwisher, McDermott, & Chun, 1997). One reason that some consider the FFA to be specific to human face processing is that the brain process responsible for the recognition of faces has been shown to differ from the process used to recognize other objects. Cases of prosopagnosia (face-blindness) and object agnosia 2 (object-blindness) show a double dissociation suggesting that the brain uses separate processes (or recognition subsystems) to accomplish face and object recognition (Farah, 2004). Behavioral evidence for separate recognition systems also exists.
Inverting (Yin, 1969) or creating photographic negatives (Galper & Hochberg, 1971) disrupt face recognition more than object recognition. If part of a face such as a nose is learned in the context of a face, testing recognition of the nose in isolation produces a recognition deficit when compared to testing recognition in the context of the whole face suggesting encoding of the relationships between parts beyond the features of the nose itself (i., the part-whole effect, Tanaka & Farah, 1993). Identifying half-faces is slower when the tested half-face is aligned with another half-face (creating a whole face) than if the halves are misaligned (i., the composite effect, Young, Hellawell, & Hay, 1987). Visual half-field studies have found that presenting faces to the left visual field (and thus to the right hemisphere) as opposed to the right visual field leads to better recognition performance, but no hemisphere advantage is typically found for basic-level object recognition (Brooks & Cooper, 2006).
Physiological evidence for this dissociation between face and object recognition comes from a variety of methods that have isolated brain responses to faces in the FFA and nearby brain regions. The FFA shows maximal activation to faces when compared to non-face objects (e., flowers, houses, chairs, etc.) in studies using fMRI (McCarthy, Puce, Gore, & Allison, 1997; Pinsk et al. Indeed, intracranial electroencephalography (iEEG) has shown a wide distribution of neurons that respond to faces over other categories of objects throughout the ventral 3 occipitotemporal cortex (Rossion, Jacques, & Jonas, 2018), and electrical stimulation of these areas can produce temporary hallucinations of faces superimposed on viewed objects (Schalk et al. It is no wonder, with the physiological evidence pointing firmly in favor of face- specificity, that the FFA has been considered by some researchers to be an area devoted exclusively to face identification.
We know that these processes for object recognition and face recognition are different. However, the issue with which this proposal is concerned is whether the underlying process responsible for the successful identification of faces is, in fact, unique to human faces. One theory that can explain how these two recognition systems differ is the coordinate relations hypothesis, which is not specific to faces. The Coordinate Relations Hypothesis The coordinate relations hypothesis states that there are two recognition systems that the brain can use to accomplish recognition tasks, and the system that the brain uses to complete a task is determined by the computational demands of the task in question.
The two recognition systems used to explain the dissociation between object identification and face identification are the categorical system and the coordinate system. These two systems were initially proposed by Kosslyn (1987) as lateralized (hemisphere dominant/specialized) systems used for both seeing and imagining (i., spatial relations theory). According to the coordinate relations hypothesis, if a visual recognition task can be accomplished using a representation of an object’s parts and the categorical relations of those parts, then the brain will use a basic-level recognition system that does not represent exact distances. This first system is the categorical system, which encodes visual primitives (e., geons, Biederman, 1987) and the relations between those primitives (e., above, below, side of).
However, if the task requires distinguishing among objects that have the 4 same parts and relations (see Figure 1), then the face identification system will be used. This second system is the coordinate system, which encodes metric data from the visual input, such as how far primitives in the representation are from a reference point (Brooks & Cooper, 2006; Cooper & Brooks, 2004; Cooper & Wojan, 2000). The basic-level system is more efficient, and so is used to satisfice a visual task whenever possible. However, the coordinate-relations hypothesis predicts that there is nothing special per se about human faces, but that rather, faces are generally subjected to the use of the coordinate system because the task of facial recognition demands it (See Figure 2).
Telling a person apart from a sheep is a trivial matter because of categorical differences in structure (e., face shape, etc.), but telling a person apart from another person or a sheep apart from another sheep requires differentiating between the same parts with the same relations (e., two eyes above a nose above a mouth). Accomplishing this task requires additional information, namely the metric distances between the parts (e., the amount of space between the eyes). The coordinate relations hypothesis posits that metric distances in visual information can be encoded. For example, for the left-side woman, the distance from the left eye to the right eye is 1.
For the right-side woman, the distance from the left eye to the right eye is 1 grid unit. This difference could be used to differentiate these women. Similarly, the coordinate relations hypothesis would predict that metric differences in sheep faces could be encoded and used to distinguish the sheep faces. 7 Alternatives to the Coordinate Relations Hypothesis Previously proposed hypotheses concerning the specificity of the FFA include the biological recognition hypothesis (Farah, McMullen, & Meyer, 1991), the expert recognition hypothesis (Diamond & Carey, 1986; Gauthier & Tarr, 1997), the subordinate- level recognition hypothesis (Gauthier, Anderson, Tarr, Skudlarski, & Gore, 1997; Gauthier, Tarr et al., 2000), and the face-specificity hypothesis (Kanwisher et al., 1997; Xu, Liu, & Kanwisher, 2005).
Each of these hypotheses, and the general pattern of findings supporting each, are discussed in turn. The biological recognition hypothesis proposes that it is not faces, per se, that the FFA responds to, but rather, biological stimuli in general such as plants and animals as opposed to non-living things (Farah, Meyer, & McMullen, 1996).