More on Recursion…

1. More on Recursion… ….with Starlings Nick Baumann Katherine Tech

2. Background • Recursion is uniquely human • Humans have: • Context-Free Grammar (CFG) • Animals have: • Finite-State Grammar (FSG)

3. Ports have IR receiver and transmitter Holes allowed probing A hopper provided food One station per animal for training Experiment Apparatus

4. Shaping & Selection • Center hole flashing LED = food • Initiation of Experiment • Learning baseline FSG/CFG • Only fast learners were used (green) • The others were dinner “The rate of acquisition varied widely among the starlings that learned the task and was slow by comparison to other song-recognition tasks.”

5. From a single adult male starling A= Rattles B= Warbles Conditions • Context-Free Grammar • A2B2 • Finite-State Grammar • (AB)2

6. Results • Nine of the eleven birds able to classify FSG and CFG sequences • Have the capacity to describe long strings – generative grammar • Baseline of n=2 • Probed birds with n=3, n=4 • Further tests done to ensure proper interpretation of data

7. Some Possibilities… • Classified patterns described by CFG/FSG grammars through • Rote Memorization of training examples • Learn only FSG and CFG is the complement set • Listening for • A/B and B/A transitions • BB, AA, and AB motif pairs

8. Rote Memorization Testing • Transferred birds abruptly from the training stimuli to new sequences • Baseline: n =2 • Example: New CFG: AAAAAABBBBBB New FSG: ABABABABA • Starlings correctly classified the new CFG and FSG sequences • Acquired general knowledge characteristic of the two grammars • Birds did not memorize the training stimuli

9. CFG as a complement set • Made 16 new sequences based on 4 agrammatical patterns • Agrammatical Patterns: AAAA, ABBA, BBBB, and BAAB • Presented among grammatical sequences • “The response patterns for the agrammatical probe stimuli differed significantly from those for new (AB)2 stimuli for all four birds, and from those for new A2B2 stimuli for three of the four birds”

10. Listening for pairs and transitions • Classifying sequences by pairs at the start or end • Ex. xxAB xxBB and AAxx ABxx • Counting A/B and B/A Transitions • Test possibility with agrammatical stimuli • End: response times similar between AAAB and BBBB and their counterpart (AB) 2 and A2B2 • Transitions: discriminate between ABBA, BAAB, AAAA and BBBB and similar times with reference

11. Is Recursion Important? • More to speech than recursion • People can still speak without it • Premack 2004 • Voluntary control of sensory-motor systems • Imitation/Teaching • Theory of the Mind • Vocabulary

12. Recursion in Humans • Marcus 2006 • Humans have better ability for recursion • No extensive training • Generalize recursion to new words

13. Are Conclusions Valid? • Is it possible for finite-state grammar to mimic context-free grammar? • Pattern recognition could lead to same result • Humans fail similar tests • The cats the dog the men walk chases run away.

14. Continued… • Perruchet and Rey 2004 • “We report an experiment replicating the results of F&H in humans, but also showing that participants learned the language without exploiting in any way the center-embedded structure. When the procedure was modified to make the processing of this structure mandatory, participants no longer showed evidence of learning.”