Headturn Preference Procedure

BITTSy was designed to allow testing using the Headturn Preference Procedure, a paradigm for which there are no other freely-available standardized test systems. Below we discuss the way HPP works, and some of its advantages.

How HPP works

Since the time it was first developed in the early 1980s (Colombo & Bundy, 1981; Fernald, 1985), the HPP has been a cornerstone method for studying early language development, and has been used in several of the most influential studies in infant speech perception (e.g., Fernald, 1985; Jusczyk & Aslin, 1995; Saffran, Aslin, & Newport, 1996, collectively cited more than 1000 times). The last substantial modifications to the method were made in the mid 1990s (Jusczyk & Aslin, 1995; Kemler Nelson et al., 1995) and current set-ups have lagged behind advances in software programming and hardware. In the standard variant, infants sit on their caregivers’ laps in a 3-walled test booth (see Fig. 3). Based on an observer's real-time coding of infant orienting behavior, a computer controls flashing lights, one on each wall of the booth, and 2 audio speakers, one under each of the side lights. Typically, trials begin with the light in front of the infant flashing, attracting the infant’s attention front and center. After the infant orients to the center, the light stops flashing and one of the two side lights begins to flash. When the infant turns towards that light, sounds begin to play from the speaker on that side; sounds continue until the sound file ends or until the infant looks away for a pre-determined amount of time (usually 2 seconds), ending the trial. By comparing infant orientation and attention to trials of different types, researchers can examine the types of sounds and sound patterns infants recognize, differentiate, or prefer. Although some studies have used HPP to test infants’ ability to discriminate between different stimuli (e.g.Nazzi et al., 2000), its most common use is to test either infants’ recognition of stimuli or their preference for specific components of their native language (see Johnson & Zamuner, 2010 for a recent review). When combined with a familiarization or training phase, this paradigm not only examines what children have already learned about their language(s), but also provides information as to what they are able to learn in the laboratory (Marcus et al., 1999; Saffran et al., 1996).

Benefits of the HPP Procedure

• HPP uses infants’ natural tendency to maintain visual orientation towards an attended sound source

  • The task puts minimal demands on the infants as compared to tasks that require children to understand verbal instructions and produce an overt reaching or verbal response.

  • This makes HPP ideal for separating differences in perceptual skills from differences in the comprehension or processing of verbal instructions.

• HPP is easy to use across a wide age-range that includes key milestones of language development.

  • HPP has been used with typically-developing children ranging from 4 months (see, for example, Mandel et al., 1995; Seidl, Cristià, Bernard, & Onishi, 2009) through 2 years (Santelmann & Jusczyk, 1998; Tincoff, 2006), a perfect range for examining early language development.

  • A unique quality of HPP is that it provides opportunities to study developmental change through cross-sectional and longitudinal studies; use of the same task across ages helps to ensure that changes are the result of cognitive/perceptual development rather than differences in task difficulty.

• HPP is extremely flexible.

  • HPP can be used with stimuli ranging in complexity from single syllables (e.g. McMurray & Aslin, 2005) to entire passages (Jusczyk & Aslin, 1995; Soderstrom & Morgan, 2007), and with both speech and nonspeech stimuli.

  • HPP has been used to examine long term memory for sound patterns presented in the lab (Houston & Jusczyk, 2003) and from naturalistic settings (Jusczyk & Hohne, 1997; Saffran, Loman, & Robertson, 2000), and to explore musical knowledge and learning (Krumhansl & Jusczyk, 1990; Saffran & Griepentrog, 2001; Saffran et al., 2000), rule learning (Marcus et al., 1999), auditory stream segregation (Newman, 2005), and knowledge of phonetic categories (McMurray & Aslin, 2005), phonotactics (Chambers, Onishi, & Fisher, 2003, in press; Jusczyk et al., 1993), and prosody (Seidl & Cristià, 2008).

• HPP maximizes research resources, compared to other infant testing procedures.

  • Sessions last approximately 10-15 minutes, which is well-matched to the attention spans of infants in the target age range. Shorter sessions maximize the number of infants who are able to complete the experimental session and provide usable data. Low attrition rate is particularly important when testing populations for whom recruitment can be difficult and costly, such as bilingual or atypical infants.

  • Observer training can be effectively accomplished in a relatively short period of time, thus maximizing research assistants’ time for collecting and analyzing data.

Opportunities for Growth with the Use of HPP

The original use of the HPP paradigm focused on typically-developing monolingual infants in the 4-12 month age range, and there are still relatively few speech perception studies with bilingual infants using HPP (e.g., Bosch & Sebastián-Gallés, 2001; Bosch & Sebastián-Gallés, 2003; Vihman et al., 2007). Although most research using HPP focuses on infants under one year of age, recent work has demonstrated the use of HPP in typically-developing infants in the 20-24-month age range and in clinical populations with children as old as 48 months (c.f., Soderstrom & Morgan, 2007; Van Heugten & Johnson, 2010). Research has also demonstrated links between early listening preferences shown through HPP and subsequent linguistic and cognitive development (Newman, Bernstein Ratner, Jusczyk, Jusczyk, & Dow, 2006). Researchers are also starting to use behavioral paradigms in concert with physiological measures, such as heart-rate and ERPs (Kooijman, Johnson, & Cutler, 2008; Panneton & Richards, under review), and have begun developing visual variants of HPP for testing American Sign Language (Baird, Seal, & DePaolis, 2010). All of these point to new ways to use this paradigm with other populations.

One limitation of previous research with HPP is that the majority of this research has used flashing lights as the primary attention-getting device, and flashing lights may not hold the attention of more cognitively-advanced participants, such as older children. Recent studies have begun showing images on flat screen monitors (Bosch & Sebastián-Gallés, 2001; Volkova, Trehub, & Schellenberg, 2006), an extension that lends itself well to testing older children in that it creates a more visually stimulating environment. BITTSy is designed to allow either the use of traditional lights, or the use of video monitors; if your test room is set up with both, you can switch between them just by what you list in your protocol file (that is, you do not need to set up your system to do one or the other; it can be set up to allow both.)

Limitations of Previous Versions of HPP

Until BITTSy was developed, there was no easily available, off-the-shelf testing system for HPP. HPP was dependent upon custom-designed hardware – the computer needed to be physically connected to the test booth as well as to an input panel which researchers use to indicate the direction in which infants orient. The input panel required specialized wiring, and response boxes needed to be created specifically for each research lab. Most researchers using HPP had to employ their own programmer and electrical engineering consultants to build the system. This limited the use of the approach to only individuals with substantial funding and technical resources and more importantly, it reduced the likelihood of new investigators implementing this methodology.

Since most researchers developed their own systems, there was no standardization, making cross-site collaborative research very difficult. This in turn limited comparative work across populations located in distinct geographical areas (e.g., work comparing infants with different language exposure). This was particularly problematic for research examining the role of different language combinations in infants raised bilingually, in that few locales have easy access to sufficiently large populations of infants raised in particular types of households.

Finally, at the time that BITTSy was created, many of the systems in use were becoming obsolete, as the timing boards and software tied to specific operating systems.