An eye-tracking study of multiply complex Dutch compounds: Preliminary results Victor Kuperman, Rob Schreuder, Harald Baayen Radboud University Nijmegen, The Netherlands

Research Goals: Exploring morphological complexity beyond the level of bi-morphemic compounds in reading. Applying the mixed-effects multiple regression technique with subjects and items as crossed random effects. Accounting for recently raised methodological issues in the analysis of visual comprehension, such as the influence of prior trials and fixations. Exploring gender difference in reading.

Materials: 1250 existing Dutch compounds with “additional” complexity (source: CELEX). Either tri-constituent compounds, or compounds with at least one affixed constituent. Mean index of complexity: 4.3 (0.7). Examples:trap-lop-er “stair walker” lof-ge-zang “song of praise” ver-zet-s-lied“song of protest” zee-man-s-kunst “sailor’s art”

Materials: 1250 neologisms built of existing Dutch words. Same requirements to the structure as with the target group. Neologisms were rated for interpretability on the 1-7 scale. Target words and fillers were presented in isolation. We are eliciting strategies for morphological parsing to explore the baseline effects.

Materials: All stimuli were limited to 12 letters in length: 8-12 letter-range. Mean word length: 11.6 (0.7) tight control for the influence of WordLength and disconfounding of WordFreq vs. WordLength and WordLength vs. LeftLength

Materials: 2500 words were presented in isolation for lexical decision, while eye movements of subjects were monitored (right-eye). 80 cm distance from the screen. Words presented in fixed-width font, size 12. Foveal view of 5.6 letters. An asterisk was presented centrally for 500 ms, then the word was displayed such that the asterisk position was always located after the 4 th letter (close to OVP). No timing on lexical decision. Drift correction after every 3d trial.

Materials: All 19 subjects were right-handed with normal or corrected-to-normal vision: 12 females and 7 males. Two hourly sessions on two different dates. Each session contained one 15-min break and 3 to 4 shorter breaks.

Data Pool: Trials with blinking or eye-tracker misreading were excluded from the data pool. Fixations that were finished after the point of lexical decision were excluded. Fixations shorter that 30 ms and longer than 1000 ms were excluded. Fixations bordering the micro-saccades (within-letter saccades) were excluded.

Data Pool: The remaining pool of valid fixations: Distribution of Fixations: Mean fixations per word: 2.7 (1.4) Progressive (86%) vs. Regressive (14%)

Dependent Variables First-fixation position (pre-defined) First-fixation duration Probability of a single fixation First saccade length Second-fixation duration Probability of having exactly two fixations Probability of regressive fixation Total number of fixations Gaze duration Third-fixation position and duration

Independent Variables: Groups Measures from previous trials and previous fixations Orthographic measures (lengths, n-gram measures) Morphological variables (word and immediate constituent frequencies) Indicators of fine-grained morphological structure (affixes and non-immediate constituents, distance from morph. boundaries) Not reported here: Lexical decision data Semantic transparency, interpretability of neologisms Paradigmatic measures (family size, entropy, cumulative root frequency, etc.)

Results: Influence of previous trials Longer lexical decision RT of the previous trial predicts: First fixation is longer (mean: 21ms) Second fixation is longer (mean: 5ms) More fixations on the word (mean: 0.9) Gaze duration is longer (mean: 70ms) Summary: Complexity of the previous task predicts more and longer fixations in the current trial.

Results: Influence of previous trials Larger trial number predicts: Less fixations on a word (0.7) Shorter gaze duration (mean: 36ms) Summary: Effects of habituation to the task.

Results: Influence of previous fixations If the first fixation is further into the word: Second fixation is shorter (mean: 44ms) If the first fixation is longer: Second fixation is shorter (mean: 25ms)

Interim Summary: Methodological Issues The influence of previous trials and of previous and following fixations on lexical processing of isolated words is on par with or exceeding the largest morphological effects. Thus, these predictors require tight experimental or statistical control.

Results: Orthographic Measures A longer word predicts: Shorter first and second fixations (45 ms; 5 ms) Total fixation number is larger (0.7 – 1.1) Gaze duration is longer (mean 5 ms) Summary: Individual fixations are shorter, but there is more of them. Effects are relatively small due to our experimental control of word length.

Results: Orthographic Measures A longer left constituent predicts: Less probable single fixation [HP 98] First fixation is shorter (mean 7ms) [11ms, HP 98] First saccade is longer (0.2– 0.5 letter-size) [0.5 ms, HP] Second fixation is shorter (5ms) [longer 6ms, ns, HP] No effect on gaze duration [HP 98] HP 98 = Hyönä & Pollatsek, JEP 1998

Results: Morphological Variables A higher compound frequency predicts: Less probable second and third fixation [PHB, 2000] First fixation is shorter (mean 10ms) [5ms, PHB] Second fixation is shorter (mean 3ms) [16ms, PHB] Gaze duration is shorter (mean 32ms) [82ms, PHB] Summary: Shorter fixations and gaze duration, higher probability of less fixations. Effects start at first fixation. PHB, 2000 = Pollatsek et al., JEP 2000

Results: Constituents A higher left-constituent frequency predicts: First fixation is shorter, especially for prefixed left constituents (mean 18ms) [9ms, HP; 8ms, AMR ] Second fixation is shorter, only for suffixed right constituents (mean 23ms) [9ms, HP] Gaze duration is shorter, especially for prefixed left constituents (mean 13ms) [87ms, HP; 27ms, AMR] Summary: Effects start at first fixation. Shorter fixations and gaze duration, higher probability of having less fixations. AMR = Andrews et al., Eur. J. Cogn. Psy. 2004

Results: Constituents A higher right-constituent frequency predicts: Second fixation is shorter, only for suffixed right constituents (mean 45ms) [8ms, PHB] Gaze duration is shorter, especially for suffixed right constituents (mean 25ms) [95ms, PHB; 15ms, AMR] Summary: Effects start at second fixation. Shorter fixations and gaze duration.

Interim Summary: Orthography and Morphology Effects reported for Finnish and English are replicated in Dutch, mostly with similar sizes. Left constituent frequency affects the first fixation duration, the right constituent frequency affects the second fixation duration: Evidence for the serial access to constituents Compound frequency starts affecting reading earlier than the right constituent frequency: Evidence for the dual route model in relatively short compounds (8-12 letters)

Results: Morphological Complexity Does complexity imply slower processing? Yes If the complexity index is higher: Gaze duration is longer (mean 8ms) If the left or the right constituent is a compound in itself (dag+boek-schrijver “diary writer”; joden-kerk+hof “synagogue”): Gaze duration is longer (12 ms, left; 13 ms, right)

Results: Morphological Variables Does complexity imply slower processing? No ver-wacht-ing+s+ge-voel-en-s “feelings of expectation” For left+suffix, interfix, right+prefix, right+suffix: Gaze duration is shorter (range: 3-15 ms)

Interim Conclusion: Sub-Constituent Complexity Complexity makes processing: Slower, if a stem is added. Faster, if an affix is added. Since affixes and stems behave differently in visual processing of words, decomposition is present. Faster processing of complex constituents than simplex constituents (Raab, 1962, Frauenfelder, Schreuder, 1992, Bertram et al., 1999). Facilitation derives from parallel processing of the stem and the whole constituent via the parsing route, as opposed to the direct route (the only option for simplex constituents).

Results: Gender Difference Males show: smaller effects of word length and left constituent length on fixation durations and gaze durations; larger inhibition effects of RTs from the previous trials on gaze duration; smaller facilitation from habituation on fixation and gaze durations. Why?

Results: Gender x Morphology Males, like females, show: facilitatory effects of word frequency facilitatory effects of constituent frequencies Sub-constituent level: Males, like females, show: inhibitory effects of the left constituent being a compound facilitatory effects of the left constituent having a prefix dagb*oekschrijververz*etslied

Results: Gender x Morphology Sub-constituent level: ver-w*acht-ing-s-ge-voel-en-s Males, unlike females, show: little or no effect of any morpheme located to the right of the initial fixation, be it a stem (inhibition) or an affix (facilitation) Women detect sub-constituent complexity better than men, while men appear to be sensitive to larger, constituent-level blocks. The difference shows up in the right part of the compound. Why?

Discussion: Gender x Morphology Possible explanation: Women have been reported to have better skills in speech production and perception, including articulation, spelling, recall of words, etc. Possibly, women have better abilities in parsing morphological structure.

Summary of Findings: Fine-grained structure (below the level of immediate constituents) affects visual processing of isolated words, Added lexical complexity inhibits reading, while added morphological complexity facilitates it. Subconstituent morphological effects interact with readers’ gender. They are observed for both genders in the left part of compounds and only for females in right parts of compounds. Evidence is found for the serial access and dual route model and previous findings in Finnish and English are replicated. Influence of previous trials and previous/following fixations needs to be taken into account.

Thank you!

Results: Constituents Why are the effects of constituent frequencies larger if there are affixes present? First fixation imposed at 4 th letter: The view of the initial letters of left constituent stem is better when the left constituent has a prefix. The average position of the 2 nd fixation is 7.7 (0.5) letters into a word. The view of final letters is better when the right constituent has a suffix [Beauvillain, JML 1996]

Results: Influence of previous trials Longer lexical decision RT of the previous trial predicts: First fixation is longer (mean 12ms) Single fixation is less probable Second fixation is longer (mean 20ms) Two-fixation scenario is less probable Total number of fixations is larger (1-1.5) Gaze duration is longer (mean 17ms) Summary: Complexity of the previous task predicts more and longer fixations in the current trial.

Results: Influence of following fixations If the fixation is the last one in the trial: First-fixation duration is longer (87 ms) First saccade is longer (0.1 letter) Second fixation is longer (15 ms) Summary: Accounting for the last fixation in simple effects and interactions with other predictors explains much variance.

Results: Orthographic Measures A longer word predicts: First fixation position is more into the word (mean 0.2 letter-size) First fixation is shorter (mean 45 ms) First saccade is longer (2.6 – 3.3 letter-size) Second fixation is shorter (mean 5 ms) Total fixation number is larger (0.7 – 1.1) Gaze duration is longer (mean 5 ms) Summary: Fixations are shorter, but there are more fixations.

Results: Morphological Complexity Does complexity imply slower processing? Yes If the complexity index is higher: Second fixation is longer (mean 34ms) Gaze duration is longer (mean 8ms) If the left or the right constituent is a compound in itself (dag+boek-schrijver “diary writer”; joden-kerk+hof “synagogue”): Second fixation is longer (9ms) Gaze duration is longer (12 ms, left; 13 ms, right)

Results: Morphological Variables Does complexity imply slower processing? No ver-wacht-ing+ s+ge-voel-en-s “feelings of expectation” For left+suffix, right+prefix, right+suffix: Second fixation is shorter (range: 20-35ms) Gaze duration is shorter (range: 5-15 ms) For left+prefix: First-fixation is shorter (3ms, below precision limit) For interfix: Gaze duration is shorter (3ms, below precision limit)

Results: Influence of following fixations If the fixation is the last one in the trial: First-fixation duration is longer (87 ms) Second fixation is longer (15 ms) Summary: Accounting for the last fixation in simple effects and interactions with other predictors explains much variance.

Results: Orthographic Measures A longer word predicts: First fixation position is more into the word (mean 0.2 letter-size) First fixation is shorter (mean 45 ms) Second fixation is shorter (mean 5 ms) Total fixation number is larger (0.7 – 1.1) Gaze duration is longer (mean 5 ms) Summary: Fixations are shorter, but there are more fixations. Effects are small due to experimental control of word length.