EXPERIMENT 2. b

Experiment 2.b was the exact same experiment as Experiments 2.a but with phonological distractors appearing at SOA +150 ms. Shifting the SOA to a later time window may allow the facilitation effect on the second word to arise. This suggestion is based on Jescheniak et al.’s (2003) graded activation account. In this account, the authors suggest that the earliest element of the utterance will receive the highest activation while the others’ will decrease.

650 700 750 800 850 900 950 1000

051015202530

Word 1 (SOA 0 ms)

Response time

Effect

650 700 750 800 850 900 950 1000

-100102030

Word 2 (SOA 0 ms)

Response time

Effect

109 Chapter 4: The investigation of the span of phonological encoding in a picture naming task

with semantic and phonological priming Elements outside the scope of phonological encoding will receive no activation and should therefore present no effect whatsoever if primed phonologically. On the contrary, primed elements being in the first position of the utterance and within the scope of phonological planning will show a clear facilitation effect. However, primed elements occurring at a later position in the utterance and being still in the scope of phonological planning will show a decrease of activation or might even present an inhibitory effect. The reason for this is that conflict will occur between the “natural” priming of the initial element of the utterance and the “induced” priming of the latter one. In Experiment 2.b, we take this account into consideration and shift the SOA to a later time window (+150 ms). If the scope of encoding is limited to W1 only, then we should observe no priming effect on W2 even when shifting the SOA to a later time window. However, if the scope of planning extends W1, then we should observe an inhibitory effect for W2 since induced priming of W2 will compete with natural priming of W1.

If the priming effect of the second element in Experiment 2.a failed to arise because of too early an SOA, then we should observe a priming effect for all the elements of the NPs for this experiment (strong facilitation effect for W1 and inhibitory effect for W2).

Method Participants

Twenty French speaking undergraduate students took part in the experiment. They received course credit for their participation. All had normal or corrected-to-normal vision.

Material

The material was the same as in Experiment 2.a.

Procedure

The procedure was exactly the same as in Experiment 2.a except that auditory distractors appeared 150 ms after picture onset (SOA +150).

Results

Voice key failures were checked and corrected with speech analyser software. Errors, no responses, technical errors were discarded from the analysis and reaction times above 1960 and below 350 ms were withdrawn from the data analysis. A total of 11% of the RTs was removed.

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Spoken latencies data were fitted with linear regression mixed models (Baayen et al., 2008) with the R-software (R-project, R-development core team 2005; Bates and Sarkar, 2007). As in Experiment 2.a we analysed separately the data where the first or the second word were primed the syntactic order condition (A+N, N+A) and distractor condition (unrelated, phonologically related) were included in a generalized mixed model as a fixed effect variables and participants and items as random effect variables. Error rates were fitted with logit mixed-effects models (Jaeger, 2008) with same random- and fixed-mixed-effects factors. We controlled by-participants and by-items random adjustments to intercepts. Results are presented in Table 14.

For the W1 priming condition we observe an interaction between distractor and syntactic order (t(1386)= 1.96, p< .049) no main effect of priming (t>1) and an effect of the syntactic order condition (t(1386)=8.41; p< .0001) with A+N sequences being faster than N+A sequences. Contrasts on the effect of priming for each syntactic structure fail to reach significance (A+N (t(670)=-1.12, p=.26) and N+A (t=(670)=1.62, p=.10).

There is no significant effects on error rate (all zs<1).

For W2 priming only the syntactic order condition yields a significant effect on RTs (t(1386)=5.13; p< .0001, all other ts<1). No effect of conditions on error rate is observed (all z<1).

Table 14

Mean RTs and SD for Each Condition at SOA +150 (in ms)

MeanSD Difference Error (%)

(ms)

Word1 Phonologically Unrelated Phonologically Unrelated

primed related related

A+N 804 (268) 787 (251) -17 1.1 0.8

N+A 864 (288) 870 (275) 6 0.9 0.9

Word 2 Phonologically Unrelated Phonologically Unrelated

primed related related

A+N 825 (262) 814 (265) -11 0.9 1.1

N+A 882 (308) 876 (275) -6 0.9 1

111 Chapter 4: The investigation of the span of phonological encoding in a picture naming task

with semantic and phonological priming DISCUSSION

Experiment 2.b was run to verify whether shifting the SOA at a later time window might lead to a priming effect on the second words of the NPs. First, priming effects observed on the first word of the sequences in Exp. 2.a disappear at SOA +150. A possible explanation is that the SOA chosen might have been too late. It is indeed difficult to determine the best time window. Second, contrary to what predicted, we do not observe a priming effect on W2 in the NPs when distractors are moved to SOA+150. Nevertheless, even though we do not report a significant effect on the second word of the NP, it is interesting to see that, as predicted by Jescheniak et al´s (2003), priming on the second word with a positive SOA follows an inhibitory pattern. As for Experiment 2.a, we displayed the data in a delta plot (Figure 14) to determine whether the phonological priming effect was modulated as a function of naming latencies. First, in agreement with the results, the graphical distribution presents a very negative slope for W2 priming. Second, Figure 14 clearly shows that failure to observe a facilitation effect is constant across time when distractors are displayed at a positive SOA (+150 ms). This suggests that the choice of a positive SOA is not adequate for investigating subject variability as a function of their naming latencies.

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Figure 14. Delta plots for the priming effect (phonologically related or unrelated) of the first word of the NP and the second word of the NP respectively at a positive SOA (+150 ms). On the x-axis is the distribution of reaction times. On the y-axis is the size of the effect (positive values represent the facilitation effect while negative values represent an inhibitory effect). The distribution of the RTs is averaged per quantile (here 5 quantiles represented by the circles on the plot) and participants.

Taken together, results from Experiment 2.a and 2.b might suggest that the selection of different SOAs for W1 (SOA 0) and W2 (positive SOA) might be more reliable and would have had allowing priming on W2 to arise. The same type of SOA for words occurring at different times in the message might interfere with encoding processes.

We will now investigate the effect of phonologically related distractors presented at a negative SOA to determine whether an early SOA might be more efficient as it leaves more time for the system to process the distractor.

113 Chapter 4: The investigation of the span of phonological encoding in a picture naming task

with semantic and phonological priming