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| The two rapid adaptation experiments reported in Fine, Jaeger, Farmer, & Qian (submitted) provide evidence that humans rapidly adjust their subjective representation of the statistics of the input in order to more efficiently process language. The study leaves open several questions. One question is, assuming adaptation is implemented via a learning mechanism of some kind, what kind? There are numerous possibilities, but in this experiment we focus on distinguishing two specific proposals. The first proposal is the one outlined in our paper, namely that the type of learning involved in adaptation is at least computationally expressible as Bayesian belief update--each sentence that comprehenders process counts as a piece of evidence that is used to update a (subjective representation of a) probability distribution over syntactic structures. This predicts that if subjects process many main verb (MV) structures such as (1), this should take probability mass away from a competing structure such as a reduced relative clause (RC), like (2). | This experiment exploits the MV/RC ambiguity, illustrated in (1)-(4). |
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| Presumably this is why garden path effects are observed with sentences like (2) in the first place (subjects have far more experience with sentences like (1)). We have extremely preliminary evidence for this in Experiment 2 of Fine et al. (submitted). In that experiment, subjects see far more RCs than they expect a priori, and relatively few MV structures (few, relative to the number of RCs). By the end of the experiment, the ambiguity effect for RCs (RTs in the bold region in 2 minus RTs in the bold region of 4) had completely disappeared, whereas the ambiguity effect for MVs (RTs in the bold region of 1 minus RTs in the bold region of 3) had increased, numerically though non-significantly. | |
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| This pattern of results is predicted by a belief-update model of learning. | |
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| By contrast, Kaschak and Glenberg (2004) offer an episodic account of syntactic adaptation which predicts a different pattern of results. Specifically, under their proposal, reading a temporarily ambiguous string like ''The experienced soldiers warned about the dangers...'' causes readers to retrieve both structures, the MV and the RC. This leaves an episodic trace for '''both''' structures, which in turn facilitates processing of both. Thus, if subjects see a bunch of sentences like (2), sentences like (1) should actually get easier to process, not harder. | The episodic processing proposal advanced by Kaschak and Glenberg predicts that readers will initially misparse sentences such as (1) as having the more frequent modifier structure (i.e., they are garden-pathed). This retrieval should subsequently facilitate processing of that modifier structure, even though the modifier interpretation is ultimately ruled out. In several reading experiments, Kaschak and Glenberg find that repeated exposure to the temporarily ambiguous non-standard structure, compared to repeated exposure to the unambiguous standard needs to be+participle structure in (3), facilitates later processing of both the non-standard needs structure (1) and the modifier structure (2), in line with the episodic processing account. |
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| This experiment provides a more direct attempt to adjudicate between these two proposals. | (5) The meal needs to be cooked given that dinner is in an hour. (standard needs) |
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| MV structures are FAR more common than RCs, so a balanced design in which MVs and RCs are interspersed (like Experiment 2 in Fine et al.) may not provide subjects with sufficient evidence against MVs to detect an actual increase in the processing cost of that structure. In order to address this, we employ a block design (below I refer to blocks as phases), which is outlined in the table below. | What does the episodic processing account say about the results reported here? Consider a temporarily ambiguous sentence of the kind employed in the experiments reported above. (6) The experienced soldiers warned about the dangers conducted the midnight raid. The episodic processing proposal advanced by Kaschak and Glenberg predicts that, in sentences such as (4), subjects will initially retrieve the MV representation at the verb warned, since there is a stronger a priori expectation for this structure than for the RC structure, and, crucially, this retrieval should subsequently facilitate processing of that structure, even though the MV interpretation is ultimately ruled out. This prediction is not supported by our experiments. On the contrary, Experiment 6 finds that repeated exposure to RCs leads to slower processing of MVs (as predicted by the hypothesis advanced here). |
Synopsis and Design
This experiment exploits the MV/RC ambiguity, illustrated in (1)-(4).
(1) MV: The experienced soldiers warned about the dangers before the midnight raid.
(2) RC: The experienced soldiers warned about the dangers conducted the midnight raid.
(3) MV (unambiguous): The experienced soldiers spoke about the dangers before the midnight raid.
(4) RC (unambiguous): The experienced soldiers who were told about the dangers conducted the midnight raid.
The episodic processing proposal advanced by Kaschak and Glenberg predicts that readers will initially misparse sentences such as (1) as having the more frequent modifier structure (i.e., they are garden-pathed). This retrieval should subsequently facilitate processing of that modifier structure, even though the modifier interpretation is ultimately ruled out. In several reading experiments, Kaschak and Glenberg find that repeated exposure to the temporarily ambiguous non-standard structure, compared to repeated exposure to the unambiguous standard needs to be+participle structure in (3), facilitates later processing of both the non-standard needs structure (1) and the modifier structure (2), in line with the episodic processing account.
(5) The meal needs to be cooked given that dinner is in an hour. (standard needs)
What does the episodic processing account say about the results reported here? Consider a temporarily ambiguous sentence of the kind employed in the experiments reported above.
(6) The experienced soldiers warned about the dangers conducted the midnight raid.
The episodic processing proposal advanced by Kaschak and Glenberg predicts that, in sentences such as (4), subjects will initially retrieve the MV representation at the verb warned, since there is a stronger a priori expectation for this structure than for the RC structure, and, crucially, this retrieval should subsequently facilitate processing of that structure, even though the MV interpretation is ultimately ruled out. This prediction is not supported by our experiments. On the contrary, Experiment 6 finds that repeated exposure to RCs leads to slower processing of MVs (as predicted by the hypothesis advanced here).
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Phase 1 |
Phase 2 |
Phase 3 |
Group 1 |
8 ambiguous RCs & 8 unambiguous RCs |
5 unambiguous MVs & 5 ambiguous MVs & 20 fillers |
5 unambiguous RCs & 5 ambiguous RCs & 15 fillers |
Group 2 |
16 fillers |
5 unambiguous MVs & 5 ambiguous MVs & 20 fillers |
5 unambiguous RCs & 5 ambiguous RCs & 15 fillers |
Group 3 |
8 ambiguous RCs & 8 unambiguous RCs |
5 unambiguous RCs & 5 ambiguous RCs & 20 fillers |
5 unambiguous MVs & 5 ambiguous MVs & 15 fillers |
Group 4 |
16 fillers |
5 unambiguous RCs & 5 ambiguous RCs & 20 fillers |
5 unambiguous MVs & 5 ambiguous MVs & 15 fillers |