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Linking performance and neural mechanisms in development and disability
Davida Teller was, at heart, a vision scientist who studied visual development. She took on this high-potential but very difficult line of research because she was utterly convinced that theoretical explanations in vision science could be tested, and perhaps falsified, by examining how vision changed as a function of infant age.
In order to achieve her lifetime goal of challenging standard vision theory using infant data, Davida needed data on infant vision that could be subjected to the same quantitative analysis and modeling as was being applied to the vision of adults at that time. Her forced-choice preferential looking ("FPL") method uses infant looking behavior to provide that data. FPL is based on two observations. First, in real life, infants clearly look at some important stimuli (e.g., the mother's face), and in the laboratory, they prefer to look at "something" (e.g., a target stimulus) rather than "nothing" (e.g., a blank screen). Second, FPL is also based on the observation that an adult can easily determine whether an infant is looking to the right or the left of the vantage point of the observer. Davida was not the first person to observe these two fundamental behaviors: particularly, Robert Fantz (1962) used dichotomous looking preference elicited by two side-by-side stimuli to study the pattern vision of infants. However, the approach taken by Fantz and others required the investigator to judge the number of looks or the total looking time the infant spent on each of the stimuli, a potentially subjective and time-consuming process. Davida's contribution was to unite the two behaviors into a two-alternative forced choice system (Teller & Bornstein, 1987) that moved the study of infant vision into the realm of discrete-trial psychophysics, which is the workhorse of the study of the vision of adults.
A typical FPL stimulus is shown in Fig. 1a. At the beginning of each trial, the observer is unaware of the left-right location of the stimulus. The trial ends when the observer judges which side of the display contains the stimulus, based only on the infant's looking behavior. If the infant subject can see the stimulus (i.e., can discriminate the stimulus from its surrounding field), he/she...