How do psycholinguists do psycholinguistics?
المؤلف:
Paul Warren
المصدر:
Introducing Psycholinguistics
الجزء والصفحة:
P6
2025-10-28
41
How do psycholinguists do psycholinguistics?
Although some of our knowledge in this field comes from introspection and the observation of daily behaviour, most of the major insights have come through the generation and testing of hypotheses through experiment. More recently, there has been a marked increase in high-tech observation, measuring brain activity while participants are engaged in language-related tasks. Because of this combination of types of evidence, psycholinguistics tends to blend the theoretical and descriptive insights of linguistics with the experimental methodology and rigour of psychology.
Observation
Sophisticated experimental procedures and equipment have only become available relatively recently, and so it is no surprise that early discoveries in psycholinguistics were based on more observational approaches. Early approaches also focused in particular on speech production, since the spoken output is most easily observed. For instance, we can note and ana lyse the occurrence of pauses and hesitations in speech, and assess these as indicators of the planning and sequencing of the spoken output. We can observe where speakers make errors, and relate these errors to hypotheses about the speech planning and production processes. We can also look at the correction of errors as an indication that speakers are monitoring their own output. Rather less often, we can note when speakers are in a tip-of-the-tongue’ state and find out from them what they can remember of an elusive word, and see what this might tell us about the processes involved in finding words.
Some of these observational techniques can be combined with experimental intervention. We will see in later chapters, for example, that researchers have run experiments designed to elicit speech errors or to induce the tip-of-the-tongue state. A range of additional tasks has been used to study both production and comprehension.
Experiment
Experimental methods have become highly sophisticated over the past half century, in particular with the ready availability of software that allows a high level of control over the presentation of stimuli and collection of data, with precise timing. Advantages of experimental over observational approaches include the reduction of observer bias and the increased control over what participants are required to do. This last point means that researchers are more easily able to isolate aspects of the pro duction or comprehension processes that they are interested in. The dis advantage of experimental approaches, however, is the relative lack of ecological validity – it is usually only in experimental settings that par ticipants are asked to make an explicit judgement about whether or not a stimulus they have heard is a word of their language, or makes sense in their language.
Typically, experimental techniques involve some kind of response time measure, where the time taken by participants to carry out some language-related task is recorded, often together with their accuracy in that task. Examples of some of these tasks can be found on the website for this book. Some response time tasks involve the notion of competing attention. That is, it is assumed that the time taken by the participant to complete the task depends on how much spare capacity they have, which will in turn depend on the nature of the linguistic processing going on at the same time. So, for instance in the click location task participants listen to an utterance that has had a non-linguistic click or beep sound added to it. Their task is to listen to and understand the utterance and at the same time to mark on a transcript of the utterance where they think the click occurred. Results from such tasks show migration’ of the click to locations other than where it actually occurred. This migration is at least in part a consequence of the fact that participants’ attention was devoted to linguistic processing. Similar effects are found in dichotic switch monitoring. In this task participants have to indicate when the speech they are listening to moves from one headphone channel to the other. They do not always do this accurately because of the linguistic processing load at the point of the switch. See Chapters 10 and 11 for examples of such tasks and how they contribute to our understanding of sentence comprehension.
Other response time tasks use reaction times as a measure of the processing speed for the item being attended to. In its simplest form, perhaps, the response time task requires participants to press a button as quickly as possible when they see or hear a word. There may be a choice of buttons, one for a positive response when the word is an actual word of the language and the other for a negative response, when the word is not an actual word. Chapters 8 and 9 discuss how the speed and accuracy of participants’ responses depend on factors such as familiarity – well-known words result in faster and more accurate responses than less well-known words.
In another button-pressing task, a participant reads a sentence on screen, with presentation of each successive word controlled by the participant’s pressing of the button. Chapters 10 and 11 give illustrations of how difficulty in interpreting the sentence at any point is reflected in the time taken to press the button to see the next word.
Carrying out a response task involves many components, some of which are assumed to be relatively invariant across different stimuli e.g. the time it takes to send a motor command from the brain to the hand to execute a button press. One study Indefrey Levelt, 2004 broke down the supposedly simple task of saying a word that names a pictured object into the components listed in Table 1.1, starting with a mapping from the picture onto a mental concept and finishing with the initiation of the spoken word. e tails will be given in the following chapters, but note for now that the most obvious influence on the time taken to initiate the response is the length of the word, since the stage labelled syllabification in the table has a duration that depends on the number of phonemes, or speech sounds, in the word. But in addition, it is important to remember that the other stages will have variable durations, depending for example on the accessibility of the word, which will vary with factors such as how often or how recently that word has been used. These are the factors that are often explored in experiments, and which require other aspects of the experiment to be held constant.
Language and the brain
It is becoming more and more usual to find studies which include monitoring of the patterns of blood flow and/or electrical activity associated with neural stimulation in the brain while a participant is carrying out some language production or comprehension task. These measures have a clear advantage over behavioural methods such as response button pressing, since they provide a more direct measure of psycholinguistic processing. Imaging techniques that measure blood flow give an indication of the areas of the brain involved in the tasks being carried out and of brain areas that have been damaged after strokes or accidents. However, they typically have relatively poor temporal resolution, and so are not ideally suited to tracking the time course of the very fast processes involved in language processing. On the other hand, techniques that measure electrical activity provide better temporal resolution but poor spatial resolution. They are therefore better suited to the measurement of the time course of processing than to the precise determination of which brain areas are responsible for various tasks.
As an example of what we can learn from neurophysiological techniques, Figure 1.3 gives a very approximate depiction of differences in brain activity levels measured in a range of tasks carried out by German participants Heim, Opitz Friederici, 2002. Brain activity was measured using functional Magnetic Resonance Imaging fMR, which tracks changes in blood flow see sidebar. An important aspect of German that is being examined here is the fact that nouns have grammatical gender which is marked through the forms of articles e.g. the word fore. For instance, the word for cat has feminine gender, so the cat is die atze’, while the word for dog has masculine gender and the dog is der Hund’.
The shaded shapes in each panel show differences in brain activity when two tasks are compared. The first panel shows areas with an increase in activity in a simple baseline speaking task BASE, compared to when the participants are at rest NLL. The baseline task is simply to say ja ja’ yes yes’ when they see a simple visual stimulus.
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