Visual World Eye-Tracking

Before reviewing how to carry out a visual world study, we introduce four important core elements that will partially determine the decisions researchers make when designing visual world experiments. These decisions will depend greatly on a number of factors including but not limited to: the resources available to the researcher in terms of equipment, the population that the researcher wants to test (e.g., children versus adults), the sampling rate of the system, and the instructions to participants. All of these are likely to be dependent on the research questions that the researcher wants to address, while one relates to equipment. As discussed in Chapter 4 (Keating, this volume), an eye-tracking setup is considerably less expensive than an ERP setup, but more expensive than typical behavioral methods which require a single PC and perhaps a button box and/or a microphone and some software (e.g., self-paced reading, see Jegerski, Chapter 2, this volume). Eye-tracking systems vary in terms of the type of hardware they use and consequently in terms of the software necessary to develop an experiment and to extract and analyze data. Studies involving children (e.g., Snedeker & Trueswell, 2004), as well as those that utilize a paradigm referred to as the looking-while-listening paradigm (Fernald, Perfors, & Marchman, 2006), employ commercial video cameras. In one version of these studies, participants sit in front of an inclined podium, where a video camera is hidden beneath the podium. The podium has a hole in the center to allow the lens of the camera to focus on the participant’s face (see Figure 5.1).