Research
The research in our laboratory is funded by a multi-year grant from the National Science Foundation. The overall aim of our research program is to determine how infants use their vision and hearing to perceive their world and to learn about its meaningful attributes. To this end, we investigate when and how various basic perceptual skills develop in infancy and how they provide the foundation for the development of basic cognitive abilities. We are particularly interested in the way babies and young children use their vision and hearing to figure out what the various objects and people in their world do, why they do it, and what their action means. For example, in some of our studies we investigate whether babies are able to perceive rhythm as a basic perceptual property. Rhythm is an important property of music and language. For example, as babies are learning language, their biggest problem is to figure out where words end and new ones begin. In an ongoing speech stream, the rhythmic pattern of language gives a young baby a particularly useful way to figure out where the words begin and end. In addition, when babies interact with adults and siblings, they get to hear and see speech and, thus, learn language. One of the questions that we have addressed in our studies is whether the synchrony between the movement of the lips and voice is important to infants' perception of other people and their speech. In some recent studies we have been investigating whether babies and children are able to perceive, learn, and discriminate sequences. Speech as well as most events around us consist of strings of words or actions that are arranged as structured sequences. In order for us to perceive the meanings that are created by the sequential structure, we must be able to perceive that structure. Our studies investigate the development of this critical perceptual and cognitive ability in early life. Finally, in our most recent work, we have uncovered some rather surprising facts about perceptual development: as we get older some of our perceptual abilities actually decline rather than improve. If you would like more details about these various studies, please read below:
Perceptual Development in Infancy
Auditory-Visual Integration
Our world is usually multisensory in nature. In other words, the people and the inanimate objects that comprise our perceptual world are usually specified concurrently by separate and distinct sensations. We can see them, hear them, and sometimes feel, smell, and taste them as well. Thus, our world is a veritable cornucopia of sensory experiences. This, however, is the very problem: how do we organize this cornucopia into meaningfully unified experiences? Fortunately, the human brain has evolved as an organ that not only receives and process this cornucopia of sensations but also unifies them into meaningful experiences that transcend the sensory modality which specifies. Thus, rather than perceiving faces and voices of the people that we interact with in our everyday world as separate features of our social world, we experience them as attributes of particular people. This ability to unify disparate sensory experiences into meaningful wholes is fundamental to adaptive functioning in the perceptual cognitive, and social domains. Therefore, as might be expected, it emerges in infancy and this laboratory was one of the first to discover when some basic intersensory integration abilities emerge in infancy and then characterize how these abilities change over early human development. There are two main cues that enable us to perform intersensory integration: time and space. As events unfold over time, their visual and auditory attributes correspond in terms of synchrony, duration, tempo, and rhythmical patterning relations. Our research investigates when in infancy the ability to respond to audiovisual events as unified entities first emerges, how it changes over early development, and how it might facilitate early learning and the acquisition of basic cognitive skills (e.g., sequence learning).
Sequence Learning
Many
events in our world occur over time. Music, dance, typing on a
keyboard, and language all illustrate the importance of
stringing together a series of elements into specific sequences
that have different meanings depending on the way the elements
are arranged. In music, a given series of notes can give rise to
very different melodies depending on the way they are arranged.
In language, the meaning of the phrase - the boy hit the tree -
has clear meaning, whereas the phrase - the tree hit the boy -
is meaningless. Finally, the behaviors of people around us
consist of strings of actions whose specific meaning depends, in
part, on the specific arrangement of their actions over time.
Indeed, we are very good at extracting and interpreting other
peoples' intentions from the sequential structure of their
actions. Given the fundamental importance of sequences for both
the production of behavior and its interpretation, it is
important to study how sequence learning skills emerge in early
human development. Currently, we are investigating the
developmental emergence of specific types of sequence learning
skills in infancy. The picture on the left shows a baby watching
as 4 different objects move and make sounds on the computer
screen. After the baby learns a particular ordering of the
objects and their sounds we then change their ordering and
measure the baby's visual attention to determine if he can
detect the change.
Perceptual Narrowing
According to conventional wisdom, as we get older our senses become sharper. Recently, however, we have found evidence that debunks that belief. In a study described in an article published in the Proceedings of the National Academy of Sciences, we have shown that some perceptual abilities actually decline during the first year of life. This surprising finding comes from a study in which we tested infants' ability to match faces and voices. Prior studies have shown that infants between 2 and 12 months of age are equally good at matching particular human faces and voices. That is, if you show side-by-side faces of the same person articulating the vowels /a/ and /i/ and, at the same time, play either vowel through a centrally placed speaker, babies will look longer at the matching visual articulation of the audible vowel. This indicates that babies can perceive the unity of the visible and audible attributes of speech. We wondered how broad this ability to make audio-visual matches is and whether it might change in development. As babies grow they acquire increasingly greater experience with human faces and voices but do not have many experiences with the faces and voices of other species. If the effects of that experience are important for the ultimate perceptual abilities of infants then it might be that this selective experience with human faces and voices over time might lead to a decline in the ability to integrate unfamiliar facial and vocal information. To test this possibility, we devised an intersensory matching task in which we showed infants side-by-side movies of a monkey face producing two types of vocalizations that monkey typically produce (either a 'coo' or a 'grunt') and then played one of these calls through a speaker placed between the two faces. "coo" "grunt" "coo"
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"coo" |
"grunt" |
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We found that younger babies matched the vocalizations to the correct faces but that older babies no longer did. This intriguing finding indicates that some intersensory integration abilities actually decline as a function of the specific experiences that babies have in their everyday world. Currently, we are in the process of designing new studies to expand on these exciting new findings.
Perceptual & Cognitive Development in Pre-School Children
Our
studies with preschoolers are an extension of our infant studies.
Their purpose is to investigate how the basic sequential perception
skills that emerge during infancy become transformed in childhood
and become incorporated into higher-level cognitive abilities that
permit children to learn and understand sequences. As children enter
the preschool years, they are faced with increasing demands to learn
and understand all sorts of sequences. For example, they need to
learn the proper sequence of actions involved in putting on their
shoes, the proper finger movements to play a particular musical
piece on a piano, or the proper way to string together a series of
different words to produce a correct and meaningful sentence. These
various abilities require that they correctly perceive the
particular sequence first and that they then understand the overall
structure of the sequence. Although preschoolers appear to exhibit
an impressive understanding of order in some situations (e.g., when
they engage in certain social routines), they have considerable
difficulty understanding order in other situations (when looking at
simple shapes that are presented one at a time on a computer
screen). In our laboratory, we are interested in the various factors
that influence young children's understanding of sequences and their
ability to perceive the specific serial ordering of the elements
that comprise those sequences. Currently, we are investigating the
idea that certain factors (such as familiarity of the context and
the presence of meaningful goals or intentions) play an important
role in the development of a basic understanding of serial order.
Please click here to learn about the methods we employ to investigate the above issues