Nichole Wojciechowski and Dr. Ross Flom, Psychology Department

Infant habituation is a common method for assessing infant cognition. Habituation means becoming accustomed to any given stimuli leading to the participant becoming bored with the given stimuli. By becoming habituated to a certain stimuli, the person or animal is then able to show discrimination, meaning they are able to tell when something is different. The procedure of infant habituation is frequently used to research infant discrimination of various stimuli. Although infant habituation is common and widely used, little is truly understood about the process that occurs. Furthermore, it is important to understand this process of how infants habituate because it may be different depending on their age. Also, a supposed “lack of ability” at one period of age may only be a sign that the infant has not reached a complete stage of familiarization or habituation. Our belief was that the younger infants may not have been able to discriminate the different musical stimuli because they were not as “deeply habituated” as the older infants. Our hypothesis was that given the more conservative criterion, the infant would successfully discriminate between the two different stimuli. A common criterion used is set at a 50% habituation, meaning the infant successfully habituates when they look 50% less than their initial looking time. The more conservative criterion we used was set at 70% from the infant’s initial looking time.

For this research project we were required to spend time every day contacting parents in Wasatch County who had infants 5- and 7-months old of age. We explained the study to them and then asked them if they were willing to volunteer for the study by bringing their infant into the lab sometime during the week. Each parent that came into the lab was debriefed further about the study and then was given the choice of reading and signing a consent form or discontinuing participation. This consent form also included a place for the infant’s name and birth information. The infant was then placed in front of a television screen. Each infant viewed a neutral picture of either a woman’s face or man’s face. This way, only the infant’s listening was assessed by hearing the auditory tracks and not by viewing the picture on the screen. Also, based on the age of the infant, the infant was then placed in a particular condition of the study, which determined if the infant would listen to sad music, happy music, or both. Following habituation infants were presented with a musical excerpt from the “opposite” category. This tested whether or not they had accurately habituated.

For each study, 2 researchers observed the infant’s looking behavior by using a small button controller in back of the television screen. This control box was connected to a computer to assure a more accurate collection of data. Infants’ looking time was the dependent variable and the computer calculated the baseline (initial looking), habituation criterion, indicated when infant had habituated, and controlled the presentation of the music stimuli (change in music selection from happy to sad or vice versa depending on the condition assigned to the infant). The criterion was set at a 70% decrement from the initial looking time for half of the participating infants and

it was set at a 50% decrement for the remaining half of participants. This means that the infant set at the 70% criterion would have to have a decline of 70% from the infant’s initial looking time, meaning the amount of time looked in the first trial.

For the criterion of 50% there were twenty-four 5- and 7-month-olds that participated. Infants were habituated to a musical excerpt rated by adults and children as happy or sad. Following habituation infants were presented with a musical excerpt from the “opposite” category. So if the infant had habituated to a musical excerpt rated as “happy” then they would then listen to one rated as “sad”. Results indicate that 5- and 7-month-olds failed to show significant discrimination (both p’s >.10).

For the criterion of 70% there were also twenty-four 5- and 7- month-olds that participated. Results showed that 5-month-olds (M = 8.4, SD = 2.1; t (23) = 12.2, p <.01) and 7-month-olds’ discrimination reached significance (M = 3.9, SD = 3.0; t (23) = 3.1, p <.05). These results told us that 5- and 7-month-olds are indeed able to discriminate happy and sad musical excerpts when the habituation criterion is increased from a 50% to a 70% decrement. The 70% is the more conservative criterion.

The results of this experiment are important because they propose that the researcher’s criterion of habituation affects whether or not the infants show discrimination. Infants who are younger are indeed able to discriminate between 2 different stimuli, specifically happy and sad music. They just required the more conservative criterion of habituation.

Although this research project yielded insight and understanding it was not without its difficulties. One of the major difficulties experienced was not being able to obtain accurate data due to researcher bias, technical error, or error due to the trial of the participant. This error led us to conduct many more runs of the study so that we could obtain reliable data to use in our results. There was sometimes a fussy child or a parent in the infant’s view, or some other type of distraction. These participants’ data could not be used because it was not valid or reliable. However; this difficult data collection allowed me to attain the experience of organizing data and maintaining a proper order of all data collected. We tried hard to only accept the data that was accurate, even if it meant conducting more studies.

If given another opportunity to do a study similar to this, are a couple of things I would do differently. The first change that I would make in this study would be to further separate the infant and the researcher so as to not create distraction. Since this study was conducted in a dark room, the researcher required a light to be able to see the data sheet and the instruments used to collect data. This light was sometimes the cause of distraction which led to error. Another aspect of the study that could have been changed was removing the parent from the view of the child completely. The parent would stand on the other side of the divider and would be able to view his or her infant without being seen by the infant. This would allow each child to focus more fully on the television screen and also allow the parent to view what was happening in the study thus rewarding both infant and parent.