Biological motion

Last updated
An example of a point light display of an American Sign Language sentence. The biological motions of the signer can be observed through the motions of white dots, as they sign a sentence. Point Light Display of ASL sentence.gif
An example of a point light display of an American Sign Language sentence. The biological motions of the signer can be observed through the motions of white dots, as they sign a sentence.

Biological motion is motion that comes from actions of a biological organism. Humans and animals are able to understand those actions through experience, identification, and higher level neural processing. [1] Humans use biological motion to identify and understand familiar actions, which is involved in the neural processes for empathy, communication, and understanding other's intentions. The neural network for biological motion is highly sensitive to the observer's prior experience with the action's biological motions, allowing for embodied learning. This is related to a research field that is broadly known as embodied cognitive science, along with research on mirror neurons.

Contents

For instance, a well known example of sensitiveness to a specific type of biological motion is expert dancers observing others dancing. Compared to people who do not know how to dance, expert dancers show more sensitiveness to the biological motion from the dance style of their expertise. The same expert dancer would also show similar but less sensitivity to dance styles outside of their expertise. The differences in perception of dance motions suggests that the ability to perceive and understand biological motion is strongly influenced by the observer's experience with the action. A similar expertise effect has been observed in different types of action, such as music making, language, scientific thinking, basketball, and walking.

History

The phenomenon of human sensitivity to biological motion was first documented by Swedish perceptual psychologist, Gunnar Johansson, in 1973. [1] He is best known for his experiments that used point light displays (PLDs). Johansson attached light bulbs to body parts and joints of actors performing various actions in the dark. He filmed these actions, yielding point lights from each bulb moving on a black background. Johansson found that people were able to recognize what the actors were doing when the PLD was moving, but not when it was stationary. Johansson's invention of PLDs inspired a new field of research into human perception. Modern technology to make PLDs involves the same principles, except that film has been replaced by multiple cameras attached to computers that construct a 3D representation of actors' movements, allowing for considerable control of the PLDs.

Interest in biological motion was renewed with the publication of a 1996 article on mirror neurons. [2] Mirror neurons were found to be active in an animal's brain both when that animal observed another animal making a movement and when that animal made the same movement. The mirror neurons were initially observed in the premotor cortex, however they were also found in supramarginal gyrus and temporoparietal junction, areas of the brain that is associated with biological motion processing. The coding of both visual and motor actions within same set of neurons suggests that biological motion understanding and perception is influenced by not only the visual information of the motion but also by the observer's experience with the biological motion.

Today, the discovery of mirror neurons has led to an explosion of research on biological motion and action perception and understanding in research fields such as social and affective neuroscience, language, action, motion capture technology, and artificial intelligence such as androids and virtual embodied agents, and the uncanny valley phenomenon.

Research on Biological Motion

Findings from research on biological motion has shown that humans are highly sensitive to biological motions of actions and those observations has developed into studies on different possible factors in the perception and understanding of the biological motions of bodily actions. Through studies with point-light display (PLD), findings in psychology and neuroscience fields has grown into a sizable body of research that stretches across different fields.

General Observations on Biological Motion

In a PLD experiment, participants are presented with a static, dynamic, or randomized dynamic white dots that consists of light sources or motion capture markers that were placed on the joints that are involved in actions for biological organisms. Even though individual dots in PLD do not show any overt visual connection with other dots, observers are able to perceive cohesive biological motion of actions in dynamic PLD. [4] Studies using PLD methods have found that people are better at identifying PLD of their own gaits compared to others. [3] People are also able to recognize different emotions in PLD. With special attention to body language, an observer can identify anger, sadness, and happiness. Observers can also identify the actors' gender with some actions in PLD.

Lesion Damage

In a large study with stroke patients, significant regions that was found to be associated with deficient biological motion perception include the superior temporal sulcus and premotor cortex. [3] The cerebellum also is involved in biological motion processing. [4]

A recent study on a patient with developmental agnosia, an impairment in recognizing objects, found that the ability to recognize the form of biological organisms through biological motion remains intact, despite deficiency in perception of non-biological form through motion. [5]

Neuroimaging

Recent cognitive neuroscience research has begun to focus on the brain structures and neural networks that are involved in biological motion processing. [2] The use of transcranial magnetic stimulation methods provided with evidence that suggests that biological motion processing occurs outside of the MT+/V5 area, which can include both visual form and motion. [6] The posterior superior temporal sulcus has been shown to be active during biological motion perception. [7] Also, premotor cortex has been shown to be active during biological motion processing, showing that the mirror neuron system is recruited for perception and understanding of PLD. [8] Further evidence from another study shows that the default mode network is essential in distinguishing between biological and non-biological motion. [9] Such findings aforementioned studies show that biological motion perception is a process that pulls in several different neural systems outside of networks involved in the visual processing of non-biological motions and objects.

Development in Children

The human perception and understanding of biological motion in animal actions develops with age, usually capping at approximately five years of age. [10] In an experiment, with three-year-old, four-year-old, and five-year-old children and adults, participants were asked to identify PLD of animals actions such as walking human, running and walking dog, and flying bird. Results showed that adults and five-year-olds were able to accurately identify animal actions. However four-year-olds and three-year-olds struggled, although four-year-olds were significantly better at identifying animal actions than three-year-olds. This suggests that our perception and understanding of biological motion and actions goes through developmental process in human children, arriving at a performance ceiling for identifying animal actions at five years.

While most animals, for example cats, tend to recognize their own species' point-light displays over others species and scrambled PLDs, [11] the three-year-olds had the most success at identifying a walking dog PLD and had the least success with a walking human PLD. A possible explanation of this contradictory results might be because of the children's small physical stature and their resulting experiences with visual perspectives: dogs are more closer in height to smaller kids, while the experience of observing and performing similar biological motions of walking human are harder to come by due to height of adults, along with their low amount of experience with walking.

In the next part of the experiment, different participants were asked to identify the same point-light display animals but with static images instead of moving dots. Five-year-olds and adults gave results of chance performance, while the younger participants were omitted due to the higher error rates from the harder nature of the task. Therefore, this experiment suggests that at five years old, we are adept at identifying animal actions and visual forms with point-light displays. This study also shows that experience with biological motion is critical for our perception and understanding of actions. [10]

Language

Humans seem to use similar cognitive functions in identifying real verbs and biologically possible motions. [12] In another experiment, researchers gave participants a lexical and action decision tasks to measure how long it took them to identify whether the words were real or the scrambled PLDs an action. Participants took much longer to identify pseudo words and scrambled PLDs. The correlation in reaction time between verb words and PLD actions was found to be rather strong (r= 0.56), while the correlation between nouns and PLD actions was much lower (r= 0.31).

Those findings suggest that humans use similar cognitive functions to identify biological motion and words, whether it is presented through written language or point-light displays. The researcher suggests that these findings supports a theoretical framework called embodied cognition, which suggests that the cognition of actions and words can be supported by the motor system. [12]

Psychophysics

Some research looks into the differences between global and local processing of biological motion; how the whole PLD figure is processed compared to how individual dots in the PLD are processed. One study investigated both types of processing in a PLD of human walking in different directions by replacing individual dots with human images or stick figures facing in different directions. [13] The results showed that the humans struggle to perceive the walking direction of the global PLD when the local dots does not face in the same direction, indicating that the brain uses a similar form-based mechanism for the recognition of both global and local stimuli during processing. The results also show that processing local images is an automatic process that can interfere with the subsequent processing of the global form of the walking PLD.

Perception of biological motion in PLD depends both on the motions of individual dots and the configuration/orientation of the body as a whole, as well as interactions between these local and global cues. [14] Similar to the Thatcher Effect in face perception, inversion of individual points is easy to detect when the entire figure is presented normally, but difficult to detect when the entire display is presented upside-down. However, recent electrophysiological work suggest that the configuration/orientation of the PLD might influence the processing PLD's motion, in the early stages of neural processing. [15]

See also

Related Research Articles

<span class="mw-page-title-main">Visual cortex</span> Region of the brain that processes visual information

The visual cortex of the brain is the area of the cerebral cortex that processes visual information. It is located in the occipital lobe. Sensory input originating from the eyes travels through the lateral geniculate nucleus in the thalamus and then reaches the visual cortex. The area of the visual cortex that receives the sensory input from the lateral geniculate nucleus is the primary visual cortex, also known as visual area 1 (V1), Brodmann area 17, or the striate cortex. The extrastriate areas consist of visual areas 2, 3, 4, and 5.

Computational neuroscience is a branch of neuroscience which employs mathematics, computer science, theoretical analysis and abstractions of the brain to understand the principles that govern the development, structure, physiology and cognitive abilities of the nervous system.

<span class="mw-page-title-main">Parietal lobe</span> Part of the brain responsible for sensory input and some language processing

The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus.

<span class="mw-page-title-main">Behavioral neuroscience</span> Field of study

Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals.

A mirror neuron is a neuron that fires both when an organism acts and when the organism observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Mirror neurons are not always physiologically distinct from other types of neurons in the brain; their main differentiating factor is their response patterns. By this definition, such neurons have been directly observed in humans and primate species, and in birds.

David J. Heeger is an American neuroscientist, psychologist, computer scientist, data scientist, and entrepreneur. He is a professor at New York University, Chief Scientific Officer of Statespace Labs, and Chief Scientific Officer and co-founder of Epistemic AI.

<span class="mw-page-title-main">Inferior temporal gyrus</span> One of three gyri of the temporal lobe of the brain

The inferior temporal gyrus is one of three gyri of the temporal lobe and is located below the middle temporal gyrus, connected behind with the inferior occipital gyrus; it also extends around the infero-lateral border on to the inferior surface of the temporal lobe, where it is limited by the inferior sulcus. This region is one of the higher levels of the ventral stream of visual processing, associated with the representation of objects, places, faces, and colors. It may also be involved in face perception, and in the recognition of numbers and words.

<span class="mw-page-title-main">Mu wave</span> Electrical activity in the part of the brain controlling voluntary movement

The sensorimotor mu rhythm, also known as mu wave, comb or wicket rhythms or arciform rhythms, are synchronized patterns of electrical activity involving large numbers of neurons, probably of the pyramidal type, in the part of the brain that controls voluntary movement. These patterns as measured by electroencephalography (EEG), magnetoencephalography (MEG), or electrocorticography (ECoG), repeat at a frequency of 7.5–12.5 Hz, and are most prominent when the body is physically at rest. Unlike the alpha wave, which occurs at a similar frequency over the resting visual cortex at the back of the scalp, the mu rhythm is found over the motor cortex, in a band approximately from ear to ear. People suppress mu rhythms when they perform motor actions or, with practice, when they visualize performing motor actions. This suppression is called desynchronization of the wave because EEG wave forms are caused by large numbers of neurons firing in synchrony. The mu rhythm is even suppressed when one observes another person performing a motor action or an abstract motion with biological characteristics. Researchers such as V. S. Ramachandran and colleagues have suggested that this is a sign that the mirror neuron system is involved in mu rhythm suppression, although others disagree.

<span class="mw-page-title-main">Luciano Fadiga</span>

Luciano Fadiga is a neurophysiologist at the Human Physiology Section of the University of Ferrara and a Senior Researcher at the Istituto Italiano di Tecnologia of Genoa, Italy.

In cognitive neuroscience, visual modularity is an organizational concept concerning how vision works. The way in which the primate visual system operates is currently under intense scientific scrutiny. One dominant thesis is that different properties of the visual world require different computational solutions which are implemented in anatomically/functionally distinct regions that operate independently – that is, in a modular fashion.

The simulation theory of empathy holds that humans anticipate and make sense of the behavior of others by activating mental processes that, if they culminated in action, would produce similar behavior. This includes intentional behavior as well as the expression of emotions. The theory says that children use their own emotions to predict what others will do; we project our own mental states onto others.

Body schema is an organism's internal model of its own body, including the position of its limbs. The neurologist Sir Henry Head originally defined it as a postural model of the body that actively organizes and modifies 'the impressions produced by incoming sensory impulses in such a way that the final sensation of body position, or of locality, rises into consciousness charged with a relation to something that has happened before'. As a postural model that keeps track of limb position, it plays an important role in control of action.

<span class="mw-page-title-main">Neural correlates of consciousness</span> Neuronal events sufficient for a specific conscious percept

The neural correlates of consciousness (NCC) refer to the relationships between mental states and neural states and constitute the minimal set of neuronal events and mechanisms sufficient for a specific conscious percept. Neuroscientists use empirical approaches to discover neural correlates of subjective phenomena; that is, neural changes which necessarily and regularly correlate with a specific experience. The set should be minimal because, under the materialist assumption that the brain is sufficient to give rise to any given conscious experience, the question is which of its components are necessary to produce it.

The concept of motor cognition grasps the notion that cognition is embodied in action, and that the motor system participates in what is usually considered as mental processing, including those involved in social interaction. The fundamental unit of the motor cognition paradigm is action, defined as the movements produced to satisfy an intention towards a specific motor goal, or in reaction to a meaningful event in the physical and social environments. Motor cognition takes into account the preparation and production of actions, as well as the processes involved in recognizing, predicting, mimicking, and understanding the behavior of other people. This paradigm has received a great deal of attention and empirical support in recent years from a variety of research domains including embodied cognition, developmental psychology, cognitive neuroscience, and social psychology.

<span class="mw-page-title-main">Vittorio Gallese</span> Italian physiologist (1959–)

Vittorio Gallese is professor of Psychobiology at the University of Parma, Italy, and was professor in Experimental Aesthetics at the University of London, UK (2016–2018). He is an expert in neurophysiology, cognitive neuroscience, social neuroscience, and philosophy of mind. Gallese is one of the discoverers of mirror neurons. His research attempts to elucidate the functional organization of brain mechanisms underlying social cognition, including action understanding, empathy, language, mindreading and aesthetic experience.

Mirror-touch synesthesia is a rare condition which causes individuals to experience a similar sensation in the same part or opposite part of the body that another person feels. For example, if someone with this condition were to observe someone touching their cheek, they would feel the same sensation on their own cheek. Synesthesia, in general, is described as a condition in which a concept or sensation causes an individual to experience an additional sensation or concept. Synesthesia is usually a developmental condition; however, recent research has shown that mirror touch synesthesia can be acquired after sensory loss following amputation.

Biological motion perception is the act of perceiving the fluid unique motion of a biological agent. The phenomenon was first documented by Swedish perceptual psychologist, Gunnar Johansson, in 1973. There are many brain areas involved in this process, some similar to those used to perceive faces. While humans complete this process with ease, from a computational neuroscience perspective there is still much to be learned as to how this complex perceptual problem is solved. One tool which many research studies in this area use is a display stimuli called a point light walker. Point light walkers are coordinated moving dots that simulate biological motion in which each dot represents specific joints of a human performing an action.

In neuroscience, predictive coding is a theory of brain function which postulates that the brain is constantly generating and updating a "mental model" of the environment. According to the theory, such a mental model is used to predict input signals from the senses that are then compared with the actual input signals from those senses. With the rising popularity of representation learning, the theory is being actively pursued and applied in machine learning and related fields.

Social cognitive neuroscience is the scientific study of the biological processes underpinning social cognition. Specifically, it uses the tools of neuroscience to study "the mental mechanisms that create, frame, regulate, and respond to our experience of the social world". Social cognitive neuroscience uses the epistemological foundations of cognitive neuroscience, and is closely related to social neuroscience. Social cognitive neuroscience employs human neuroimaging, typically using functional magnetic resonance imaging (fMRI). Human brain stimulation techniques such as transcranial magnetic stimulation and transcranial direct-current stimulation are also used. In nonhuman animals, direct electrophysiological recordings and electrical stimulation of single cells and neuronal populations are utilized for investigating lower-level social cognitive processes.

Valeria Gazzola is an Italian neuroscientist, associate professor at the Faculty of Social and Behavioral Sciences at the University of Amsterdam (UvA) and member of the Young Academy of Europe. She is also a tenured department head at the Netherlands Institute for Neuroscience (NIN) in Amsterdam, where she leads her own research group and the Social Brain Lab together with neuroscientist Christian Keysers. She is a specialist in the neural basis of empathy and embodied cognition: Her research focusses on how the brain makes individuals sensitive to the actions and emotions of others and how this affects decision-making.

References

  1. 1 2 Blakemore, Sarah-Jayne (2001). "From the perception of action to the understanding of intention". Nature Reviews Neuroscience. 2 (8): 561–567. doi:10.1038/35086023. PMID   11483999. S2CID   53690941.
  2. 1 2 Rizzolatti, Giacomo; Sinigaglia, Corrado (2016-10-20). "The mirror mechanism: a basic principle of brain function". Nature Reviews Neuroscience. 17 (12): 757–765. doi:10.1038/nrn.2016.135. ISSN   1471-003X. PMID   27761004. S2CID   13153411.
  3. Saygin, A. P. (2007). "Superior temporal and premotor brain areas necessary for biological motion perception". Brain: A Journal of Neurology. 130 (Pt 9): 2452–2461. doi: 10.1093/brain/awm162 . PMID   17660183.
  4. Sokolov, A. A.; Gharabaghi, A.; Tatagiba, M. S.; Pavlova, M. (2009). "Cerebellar Engagement in an Action Observation Network". Cerebral Cortex. 20 (2): 486–491. doi: 10.1093/cercor/bhp117 . PMID   19546157.
  5. Gilaie-Dotan, S.; Bentin, S.; Harel, M.; Rees, G.; Saygin, A. P. (2011). "Normal form from biological motion despite impaired ventral stream function". Neuropsychologia. 49 (5): 1033–1043. doi:10.1016/j.neuropsychologia.2011.01.009. PMC   3083513 . PMID   21237181.
  6. Mather, G.; Battaglini, L.; Campana, G. (2016). "TMS reveals flexible use of form and motion cues in biological motion perception" (PDF). Neuropsychologia. 84: 193–197. doi: 10.1016/j.neuropsychologia.2016.02.015 . PMID   26916969.
  7. Grossman, E.; Blake, R. (2002). "Brain areas active during visual perception of biological motion". Neuron. 35 (6): 1167–1175. doi: 10.1016/s0896-6273(02)00897-8 . PMID   12354405.
  8. Saygin, A.P.; Wilson, S.M.; Hagler Jr, D.J.; Bates, E.; Sereno, M.I. (2004). "Point-light biological motion perception activates human premotor cortex". Journal of Neuroscience. 24 (27): 6181–6188. doi: 10.1523/jneurosci.0504-04.2004 . PMC   6729669 . PMID   15240810.
  9. Dayan, E.; Sella, I.; Mukovskiy, A.; Douek, Y.; Giese, M. A.; Malach, R.; Flash, T. (2016). "The default mode network differentiates biological from non-biological motion". Cerebral Cortex. 26 (1): 234–245. doi:10.1093/cercor/bhu199. PMC   4701122 . PMID   25217472.
  10. 1 2 Pavlova, Marina (April 24, 2001). "Recognition of point-light biological displays by young children". Perception. 30 (8): 925–933. doi:10.1068/p3157. PMID   11578078. S2CID   12083203.
  11. Blake, Randolph (1993-01-01). "Cats Perceive Biological Motion". Psychological Science. 4 (1): 54–57. doi:10.1111/j.1467-9280.1993.tb00557.x. ISSN   0956-7976. S2CID   145194874.
  12. 1 2 Bidet-Ildei, Christel; Toussaint, Lucette (2014-09-20). "Are judgments for action verbs and point-light human actions equivalent?". Cognitive Processing. 16 (1): 57–67. doi:10.1007/s10339-014-0634-0. ISSN   1612-4782. PMID   25238900. S2CID   15153894.
  13. Kerr-Gaffney, J. E.; Hunt, A. R.; Pilz, K. S. (2016). "Local form interference in biological motion perception". Attention, Perception, & Psychophysics. 78 (5): 1434–1443. doi:10.3758/s13414-016-1092-9. PMC   4914516 . PMID   27016343.
  14. Mirenzi, A; Hiris, E (2011). "The Thatcher effect in biological motion". Perception. 40 (10): 1257–1260. doi:10.1068/p7077. PMID   22308898. S2CID   43114908.
  15. Buzzell, G; Chubb, L; Safford, A. S.; Thompson, J. C.; McDonald, C. G. (2013). "Speed of human biological form and motion processing". PLOS ONE. 8 (7): e69396. Bibcode:2013PLoSO...869396B. doi: 10.1371/journal.pone.0069396 . PMC   3722264 . PMID   23894467.