This research was supported by an NSF Graduate Research Fellowship to Danielle R. Perszyk and a NIH grant to Sandra R. Waxman (R01HD083310).

The following procedures were approved by the Northwestern University Institutional Review Board and informed consent was obtained from the caregivers of all infants. We recruited infants being raised in environments with more than 50% exposure to English11,17. Infants in all experiments first listened to a soundtrack in which we manipulated their exposure to either lemur vocalizations or backward speech; they then participated in an object categorization task. W...

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Here we outline a procedure for examining the role of experience in linking sounds and core cognitive processes early in infancy. Our combined experiments document the first evidence that experience plays a central role in guiding infants to specify which signals, from a broad initial set of possibilities, they will harness to core conceptual processes that ultimately provide the foundations of meaning. They also reveal an intricate interface between nature and nurture: Although experience plays little role, if any, in d...

Human infants are born ready to acquire language, a cultural and cognitive tool that defines us as a species and fundamentally shapes our development. Central to our capacity for learning language are two unique features of human development: Our altriciality and our powerful learning strategies. Together, these features unlock a remarkable degree of early plasticity that enables infants to be highly attuned to input from their environments. For example, although infants come into the world with a set of perceptual preferences and discriminatory capacities sufficiently broad to include the faces and voices of human and nonhuman primates, within months they narrow these preferences to exclusively human signals1,2,3. This process of perceptual narrowing is adaptive on two counts: It increases the signal-to-noise ratio of relevant communicative signals &#8212; those that will guide infants to efficiently and accurately navigate their complex social world &#8212; and it paves the way for integrating information across perceptual modalities (e.g., integrating faces and voices)4 &#8212; an essential element for the multimodal nature of human language. Moreover, because of infants&#39; early plasticity, perceptual narrowing can be prevented or reversed with exposure to nonnative signals (e.g., nonnative language, nonhuman faces, foreign musical rhythms)5,6,8. This illustrates that perceptual narrowing is experience-driven.
Yet to master their native language, infants must do more than tune in to the faces and voices of its speakers. The power of human language is inextricably linked to cognition9. Incredibly, even in their first year of life, infants have begun to link language and cognition: Simply listening to human language promotes infants&#39; ability to form object categories, a building block for their cognition10,11,12.
This is not to say that infants can only form object categories if they are listening to language. On the contrary, decades of research reveal that infants in their first months of life can form at least some object categories in the absence of any sounds13. But not all object categories are equally easy for infants to form. The slightly more difficult categories provide a powerful opportunity to uncover what effect, if any, language may have on infant categorization. To do so, researchers identify object categories that are more difficult for infants to discern in the absence of other supporting information (like language) and then ask whether language (and other sounds) offer infants any advantage in categorization.
Using this logic, an early link between language and object categorization was documented in a novelty preference paradigm designed to accommodate very young infants (Figure 1b)11. This paradigm has two phases. During the familiarization phase, all infants view images of a series of distinct objects (e.g., dinosaurs) presented sequentially in conjunction with a sound. During the test phase, all infants view two new images in silence: One is a new member of the now-familiar category (e.g., another dinosaur) and the other is a member of a novel category (e.g., a fish). Infants&#39; looking time at test serves as an index of categorization. If infants form the category during familiarization, then at test they should distinguish the novel from the familiar image. If infants fail to do so, then at test they should perform at chance14,15,16.
The results were striking. At 3, 4, and 6 months, infants listening to language during familiarization &#8212; but not tone sequences &#8212; successfully formed object categories11,17. Surprisingly, language is not the only sound that exerts this cognitive advantage: At 3 and 4 months, listening to vocalizations of nonhuman primates (Madagascar, blue-eyed lemur: Eulemur macaco flavifrons) confers the same cognitive advantage as human vocalizations17. By 6 months of age, however, infants have tuned this initially broad link specifically to human vocalizations; lemur vocalizations no longer exert an advantageous effect on infant categorization17.
But what mechanism underlies infants&#39; increasing precision in linking language and cognition? Here, we consider the contribution of infants&#39; experience. Does infants&#39; rich experience with human language (and their dearth of experience listening to lemur vocalizations) play a role as they narrow the link between initially privileged signals (e.g., human and nonhuman primate vocalizations) and the core cognitive process of object categorization? Certainly, we cannot test this by manipulating infants&#39; exposure to language. But we can manipulate their exposure to lemur vocalizations. We focus on infants at 6 and 7 months of age &#8212; infants who, in the absence of exposure, no longer link lemur vocalizations and object categorization17. In Experiment 1, we ask whether brief exposure to lemur vocalizations permits them to preserve the link between this signal and object categorization. In Experiment 2, we ask whether brief exposure to backward speech &#8212; a signal that consistently fails to support object categorization at any age17 &#8212; also promotes object categorization. In Experiment 3, we put the question of exposure to a more stringent test, examining whether more prolonged exposure to lemur vocalizations permits them to preserve their initially-broad link.

<table border="0" cellpadding="0" cellspacing="0" width="586">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laptop 1</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Use for presenting exposure soundtrack; preferably using iTunes Visualizer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laptop 2</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for programming and presenting categorization task</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laptop 3 (optional)</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for coding infant looking behavior (can also use one of the above laptops)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Coding software</td>
			<td style="width:84px;">SuperCoder</td>
			<td style="width:119px;"></td>
			<td>Use for coding infant looking behavior</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Video recorder</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for recording infants&#39; face (looking behavior during categorization task)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Mixer</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for integrating information from the video recorder (infant looking behavior) and the visual stimuli (categorization task)&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">DVD player</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for recording the input from the video recorder (infant looking behavior)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Television</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for viewing input from mixer (screen-in-screen; categorization task in corner of screen showing infant looking behavior)&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Projector</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for projecting visual stimuli of categorization task on screen</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Speakers</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for presenting auditory stimuli during categorization task</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Blacked-out sunglasses</td>
			<td style="width:84px;"></td>
			<td style="width:119px;"></td>
			<td>Use for blocking caretaker&#39;s vision during categorization task</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Statistical analysis software</td>
			<td style="width:84px;">R</td>
			<td style="width:119px;"></td>
			<td>Use for analyzing infant looking behavior</td>
		</tr>
	</tbody>
</table>

experience is instrumental in tuning a link between language and cognition: evidence from 6-  to 7- month-old infants' object categorization

At birth, infants not only prefer listening to human vocalizations, but also have begun to link these vocalizations to cognition: For infants as young as three months of age, listening to human language supports object categorization, a core cognitive capacity. This precocious link is initially broad: At 3 and 4 months, vocalizations of both humans and nonhuman primates support categorization. But by 6 months, infants have narrowed the link: Only human vocalizations support object categorization. Here we ask what guides infants as they tune their initially broad link to a more precise one, engaged only by the vocalizations of our species. Across three studies, we use a novel exposure paradigm to examine the effects of experience. We document that merely exposing infants to nonhuman primate vocalizations enables infants to preserve the early-established link between this signal and categorization. In contrast, exposing infants to backward speech &#8212; a signal that fails to support categorization at any age &#8212; offers no such advantage. Our findings reveal the power of early experience as infants specify which signals, from an initially broad set, they will continue to link to cognition.

Using the procedures outlined above (Figure 1), we ran three experiments to test the effects of exposure as infants refine the links between certain sounds and cognition.
Results of Experiment 1 revealed that brief exposure to lemur vocalizations had a striking effect. Seven month-olds exposed to lemur vocalizations reliably preferred the novel test image, M = 0.57, SD = 0.09; t(13) = ...

Watch this Scientific Journal Video about Experience is Instrumental in Tuning a Link Between Language and Cognition: Evidence from 6-  to 7- Month-Old Infants' Object Categorization at JoVE.com

Experience is Instrumental in Tuning a Link Between Language and Cognition: Evidence from 6-  to 7- Month-Old Infants' Object Categorization

At 3-4 months, listening to human and nonhuman primate vocalizations boosts infants&#39; cognition; by 6 months, only human vocalizations exert this cognitive advantage. We describe an exposure manipulation that reveals the powerful shaping role of experience as infants specify which sounds to link to cognition and which to tune out.

At birth, infants not only prefer listening to human vocalizations, but also have begun to link these vocalizations to cognition: For infants as young as ...

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.

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