Wednesday, July 24, 2013

Swinney: "Lexical Access during Sentence Comprehension" (1979)

In 1975, David Swinney and and David Hakes published a study which provided some evidence that irrelevant meanings of ambiguous words are never retrieved from memory if the context is strongly biased against them.

This prompted a reinterpretation of previous results showing the opposite, pointing to the strength of the context as the relevant independent variable.

The "On Hold" Paradigm

The paradigm they used in the 1975 paper was a phoneme recognition task. They played tape recordings of sentences to their subjects, asking them to push a button as soon as they heard a word beginning with a specific sound (say, /k/ as in cat).

This is more difficult and takes more time if the target comes immediately after an ambiguous word:
  • … he found several bugs in the corner of his room. (ambiguous)
  • … he found several insects in the corner of his room. (unambiguous)
However, the crucial manipulation Swinney and Hakes performed was to see whether this effect still held up when the context was strongly biased towards one of the two meanings of the word:
  • … he found several spiders, roaches, and other bugs in the corner of his room.
In the 1975 experiment, they found that it did not: Including a strongly disambiguating context effectively brought the reaction time down to the level of unambiguous words. This supported the hypothesis that meaning on the sentence level could affect lexical access.

The Multitasking Paradigm

In the 1979 paper, however, Swinney argued that this effect might only have occurred because of the relatively large time lag between prime and target (p. 647). He was thus interested in devising an experimental paradigm that could manipulate the width of this gap more directly.

The solution to this problem is a cross-modal priming design: The subject listens to the sentence being read aloud, but simultaneously has to solve a lexical decision task on a screen. This way, the target and prime can be timed relative to each other in any way you like.

So for example, you might be exposed to the following stimulus:
  • Voice: … he found several spiders, roaches, and other bugs [Screen: SPY] in the …
Your task is then to decide, as quickly as possible, whether the target word is an actual English word or not. After the experiment, you are also quizzed on the sentence in the headphone to make sure that you were listening (and not just focusing on the visual task).

The Vanishing Priming Effect

The results of the experiment can roughly be summarized as follows:
No facilitation
Three syllables
No facilitation
No facilitation
An "appropriate" meaning is here one fits the meaning of the word as used in the sentence (e.g. roaches and bugs – ANT). An "inappropriate" one is a word that fits a different sense of the word (e.g. roaches and bugs – SPY). The "unrelated" is a real English word that doesn't have any specific relation to the prime (e.g., SEW).

The thing to notice about this table is the top middle cell: When there is no delay, even contextually inappropriate meanings are primed; however, after less than half a second, this effect has decayed to an insignificant level.

I remember reading in other texts that the exact time frame in which the priming effect is present is about 200 milliseconds. I don't remember where I picked up that number, though.

1 comment :

  1. Thanks for the overview of the paradigm! Gernsbacher did experiments similar to the Swinney one, manipulating SOA among other things. Check out Gernsbacher, M. A. (1991). Cognitive processes and mechanisms in language comprehension: The structure building framework. In G. H. Bower (Ed.), The psychology of learning and motivation (pp. 217-263). New York: Academic Press.

    It is available here: