Age of acquisition and frequency of occurrence: Implications for experience based models of word processing and

sentence parsing

Marc Brysbaert

A rare phenomenon inpsychological research

• All researchers agree …

• … that word recognition depends on word frequency.

• High-frequency words are recognised faster than low-frequency words.

Frequency effectin sentence parsing?

• More controversial• Is sentence parsing based on principles or on

experience?• Examples of experience-based accounts: tuning

hypothesis, probabilistic models, neural networks

• This talk is on lexical processing, but the principles also apply to experience-based models of sentence processing.

How do we measureword frequemcy?

• Word frequency is the frequency (per million) with which words are encountered in a representative corpus of text or (more recently) speech.

• As it happens, virtually all corpora are based on texts written and read or spoken by adults.

Assumptions

• Either frequency of words in adulthood = frequency of words in childhood

• or only words encountered in the last years matter

Testing the assumptions

• Frequency childhood = adulthood?– ambulance : adults = 15 / million

children = 86 / million– ancestor : adults = 15 / million

children = < 1 / million

• It does not matter?– Morrison & Ellis (1995) : words like ambulance are

named 30 ms faster than words like ancestor (effect of 80 ms in LDT)

Gerhand & Barry (1999)

The AoA effect:definition

• Stimuli (words) that have been acquired early are processed faster than stimuli that have been acquired later, even when they are matched on frequency.

• AoA measured with rating scales or by directly looking at the performance of children (r = .75).

The AoA effect:explanations

• Three classes of explanations:1. Frequency and AoA have a different origin

• frequency effect strong at input stages; AoA effect strong at verbal output stages

• effect of AoA in the organisation of the semantic system

2. Frequency and AoA have the same origin• cumulative frequency instead of frequency• learning in a connectionist model with distributed

representations (loss of plasticity)

The AoA effect:explanations

• Three classes of explanations:1. Frequency and AoA have a different origin

2. Frequency and AoA have the same origin

3. Effects of AoA are due to bad frequency measures• Higher correlation with frequency when measures take

into account childhood frequencies (Zeno et al.)

• Higher correlation with frequency when measures are based on film subtitles than on books (New et al., 2007)

The AoA effect:explanations

• Brysbaert & Ghyselinck (Visual Cognition, 2006)– to decide between the first two classes, we have

to look at the correlation between the frequency effects and the AoA effects across tasks

– if both effects have the same origin, there should be strong positive correlation between the magnitudes of the effects

– if the effect of AoA is due to cumulative frequency, then AoA < freq

Why the effect of AoA < the effect of frequency according to the cum hyp

• High frequency word > 50 / million• Low frequency word < 5 / million• This gives a ratio > 10:1

• Early acquired words < 5 yr (15 yrs ago)• Late acquired words > 15 yr (5 yrs ago)• This gives a ratio of 3:1

• So, effect AoA = 1/3 effect frequency

Gerhand & Barry (1998,1999a,b)

Ghyselinck et al. (2004)

Interim summary

• For many tasks, there is perfect correlation between the frequency effect and the AoA effect.

• This suggests that both effects are the result of the same learning process (futile to look for tasks that would show a frequency effect but no AoA effect).

• The AoA effect is too big for the cumulative frequency hypothesis.

The connectionist account of AoA

• Ellis & Lambon-Ralph (2000)

• Simple network: 100 input nodes, fully connected to 50 hidden nodes, fully connected to 100 output nodes

• « Words » defined by arbitrary patterns of 0 (80%) and 1 (20%)

• Groups of « words » entered at different times.

Discussion with Zevin & Seidenberg (2002)

• Z&S : an AoA effect that is larger than predicted on the basis of the cumulative frequency hypothesis will be found only when there is an arbitray mapping between input and output.

• Otherwise, the late-acquired patterns profit from the connections made by the early acquired patterns (is the case for word naming).

Recapitulation claimBrysbaert & Ghyselinck, 2006

• if the AoA and the frequency effect have the same origin, there should be strong positive correlation between the magnitudes of the effects

Correlation between AoA effect and Frequency effect

y=-11.309+1.118*x+eps

Age of Acquisition effect

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In search of the frequency-independent AoA effect in picture naming

1. Semantic origin of AoA– Brysbaert et al. (2000): picture naming

requires semantic mediation; hence semantic origin of the frequency-independent AoA effect.

– Steyvers & Tenenbaum (2005): growing network

In search of the frequency-independent AoA effect

• problem: no evidence for a frequency-independent AoA effect in semantic decision tasks (there is an AoA effect in these tasks, but it looks like it is the frequency-related AoA effect)

In search of the frequency-independent AoA effect

2. The lexical-semantic competition hypothesis– the frequency-independent effect is due to the

transition from semantics to verbal output– when we name a picture, initially many semantically

related names (lemmas) become activated, and selecting the correct name requires a competition between the different candidates

– hypothesis: early acquired lemmas are stronger competitors than late acquired lemmas (e.g., CAT is a stronger competitor for the naming of LION than vice versa)

Belke et al. (2005)

• Made use of the semantic blocking effect.

• It is more difficult to name pictures repeatedly if they are part of a semantically homogeneous set than if they are part of a semantically heterogeneous set.

Homogeneous condition

Heterogeneous condition

Belke et al. (2005)

• On the basis of the previous finding, we predicted that the blocking effect would be larger for late acquired words than for early acquired words

experiment

• 36 participants

• 16 pictures with early-acquired names and 16 pictures with late-acquired names

• matched on visual similarity, frequency, name length,…

• stimuli presented 6 times per block

• homogeneous and heterogeneous lists in different blocks (counterbalanced)

orange banana pear carrot

lion frog spider rabbit

scissors paintbrush ladder hammer

jumper trousers dress shoe

Early acquired stimuli

pepper cherry onion lettuce

ostrich eagle beetle camel

chisel pliers spanner broom

tights shawl mitten waistcoat

Late acquired stimuli

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In search of the frequency-independent AoA effect

3. Picture naming is not always semantically mediated– Funnell et al. (2006)– There is a difference in learning experience

between young and old children.– Young children learn about things by seeing

them (either in real or in pictures).– Older children learn about things by having them

described

In search of the frequency-independent AoA effect

• Funnell et al.– Pictures of early acquired objects are named

faster, because there is a direct link between the input stimulus and the name.

– Pictures of late acquired objects are named slower, because the naming requires semantic mediation

Conclusions

• AoA as part of the cumulative frequency seems to be a given.

• Question whether AoA has an effect over and above cumulative frequency: looks probable (plasticity in model)

• Still uncertainty about what causes the frequency-independent AoA effect in picture naming

Reading list

• Brysbaert, M. & Ghyselinck, M. (2006). The effect of age of acquisition: Partly frequency related, partly frequency independent. Visual Cognition, 13, 992-1011.

• Johnston, R.A. & Barry, C. (2006). Age of acquisition and lexical processing. Visual Cognition, 13, 789-845.

• Juhasz, B.J. (2005). Age-of-acquisition effects in word and picture identification. Psychological Bulletin, 131, 684-712.