Meyera


BBS
a
a	People
a

Research strategy
In most experiments conducted by the members of the group, participants are asked to name or describe objects or events they see. Their speech is recorded on tape so that researchers can analyse what they said, when they hesitated or made speech errors. In addition, researchers are often interested in the speakers’ speech onset latencies and speech rates because they reflect on the difficulty of the speech planning processes. Finally, it is sometimes useful to monitor the speakers’ eye movements because they show which parts of a picture attract the speakers’ attention and in which order and for how long they are processed. This information can be linked to the record of the speech output in order to study how speakers co-ordinate speech planning and speech output in time (see Figure 2).

Facilities
The Centre houses test rooms dedicated to speech production research. The laboratory computers and associated software (NESU) can be used to displays images for very short (16 ms) or longer time periods (several seconds) and to measure the speakers’ speech onset latencies. Picture onset and offset times can be pre-programmed or determined on-line depending on properties of the participants’ speech. Audio-equipment is available to present auditory stimuli (tones or speech) and to record the speakers’ speech for later analyses. In one room, there is an SMI HiSpeed-2D eyetracker (see Fig. 1). The eye movements can be recorded for off-line analyses, and they can be used on-line to trigger gaze-dependent display changes.

Basic findings
When speakers name or describe sets of objects they haven’t seen before, their eye movements are tightly co-ordinated with their speech.output. They usually look at each object just before naming it (see Figure 2) and their gaze remains on the object until they are about to say the last word of the phrase referring to the object. When speakers use a single syllable to name an object (“dog”), they will usually fixate the object for a much shorter time (about 500 ms) than when they use a longer expression (“the little brown dog”, 1300 ms). These results suggest that, contrary to widely held believes, speakers produce descriptions in a very sequential fashion, completing all planning for one object and its name before starting to process another object.

Repeated reference
When speakers refer again to objects they have named before, they usually look at the objects again. For instance, when speakers produce utterances such as “The dog next to the tree is brown”, they usually look at the dog twice, shortly before saying “dog” and shortly before saying “brown”. Sometimes, however, speakers refer to known objects without looking at them again. This is particularly likely to happen when the referring expression is short and high in frequency (e.g., a pronoun such as “it”). We assume that as default speakers plan an eye movement to each object they refer to. However, when an appropriate referring expression becomes available very rapidly (as may be the case for pronouns), the planned eye movement to the object may be cancelled and replaced by an eye movement to another object.

Generating sentences
When speakers describe simple events and select syntactic structures (“The man gives the boy a key” or “The man gives a key to the boy”), their gaze patterns become more complex, but they are far from chaotic. We observe that speakers often first fixate the middle of the display, which may be a good vantage point to gain an overview of the scene and identify the type of action that is occurring. After that brief preview phase, speakers tend to fixate upon the entities they name in the order of mention. The temporal co-ordination between eye gaze and speech is similar to the co-ordination observed in multiple-object naming.

References
Levelt, W.J.M., Roelofs, A. & Meyer, A.S. (1999). A theory of lexical access in language production. Behavioral and Brain Sciences, 22, 1-38.

Meyer, A.S. & Bock, K. (1999). Representations and processes in the production of pronouns: Some perspectives from Dutch. Journal of Memory and Language, 41, 281-301.

Meyer, A.S., Sleiderink, A.M. & Levelt, W.J.M. (1998). Viewing and naming objects: Eye movements during noun phrase production. Cognition, 66, B25-B33.

Meyer, A.S. & Meulen, F.F. van der (2000). Phonological priming of picture viewing and picture naming. Psychonomic Bulletin & Review, 7, 314-319.

Meulen, F.F van der, Meyer, A.S. & Levelt, W.J.M. (2001). Eye movements during the production of nouns and pronouns. Memory and Cognition, 29, 512-521.