The overall goal of this procedure is to identify the effects of experience in shaping infants'early links between sounds and core cognitive processes. This method can help answer key questions in the field of infant cognition. For example, how do infants begin to establish foundational links between the sounds they hear and the objects and events they see in the world?
Answers to these questions can advance our understanding of the processes that guide early language and conceptual development. The main advantage of this technique is that it can help us disentangle the relative effects of nature and nurture in processes that support infants'language and conceptual development. Begin by using audio editing software to import a piece of classical instrumental music.
Select and extract a portion of the piece that is approximately four minutes in duration, and delete the rest. Next, use this software to create two distinct soundtracks:one for lemur vocalizations, and the other for backwards speech. To create the lemur soundtrack, insert eight of the lemur vocalization sound files into various places throughout the music.
Next, highlight each of the eight distinct lemur files one at a time, select Copy, and then paste it in another place throughout the four-minute classical music clip. Insert each lemur file two times in a pseudorandomized order to result in a five minute soundtrack where no two identical vocalizations occur in a row. Additionally, be sure to insert the vocalizations at irregular intervals throughout the soundtrack, and do not place them at musical phrase boundaries.
Next, repeat this five-minute soundtrack by highlighting the five-minute section and selecting Copy. Then, place the cursor at the end of the five-minute section and click Paste. Finally, repeat this procedure to create another ten-minute soundtrack, using eight distinct samples of backwards speech, and the same music clip.
Begin by placing the infant close to the caregiver, or on their lap, in a quiet area. Then, place a laptop or tablet within the infant's viewing range and present the lemur soundtrack once for infants in that condition. Next, for the categorization task, connect a laptop to two pieces of equipment:a screen in a semi-darkened test room to display the categorization task, and a projector to present the task onto the screen.
Then, escort the caregiver to the testing room and seat them on a chair four feet away from a five by five foot screen. Place the infant on the caregiver's lap, facing forward. Instruct the caregiver to remain quiet and still throughout the duration of the task, and to keep their infant centered, using their midline as a guide.
Provide the caregiver with a pair of blacked out glasses to ensure that they cannot see the visual materials. Then, turn on the projector as well as the recording equipment to capture the infant's behavior throughout the task. Finally, begin the categorization task by pressing Run in the presentation software, and present the lemur condition.
For infants in the backwards speech condition, repeat the same procedure with a corresponding soundtrack and visual materials. Results revealed that brief exposure to lemur vocalizations had a striking effect. Infants reliably preferred the novel test image, indicating that they had formed the object category.
In contrast, infants brief exposure to backwards speech had no effect. Seven month olds performed at chance. Lastly, six month olds who had not heard the lemur vocalization for days nonetheless successfully formed object categories.
Their successful categorization parallels that of infants who had heard lemur vocalizations moments before the categorization task. This exposure paradigm can be completed in 20 minutes if performed properly. By attempting this procedure, it's important to remember to keep the infant's environment calm and quiet, with the exception of the experimental sounds they're listening to.
Following this procedure, other methods, like EEG, can be used to answer additional questions. For example, what are the neural correlates of the effects of exposure? After watching this video, you should have a good understanding of how to provide infants with exposure to various sounds, and how to test the effects of that exposure to infants'establishment of links to cognition.
And remember, working with infants can be tricky. It's important to keep them calm and engaged throughout the procedure.
