What do dolphins understand about hidden objects?

1. What do dolphins understand about hidden objects? A study conducted by Kelly Jaakkola, Emily Guarino, Mandy Rodriguez, Linda Erb, and Marie Trone Presented to you by Ngoc and Adrielle

2. Introduction • Ability to track objects associated with spatial cognition • Object permanence “ability to mentally represent and reason about objects that have disappeared from view”

3. Introduction • Piaget-six stages of object permanence. • Stage 6 = ability to track movements of hidden objects • Marks emergence of new representational capacity. • Perner-invisible displacement task one of several abilities that show capacity for secondary representation.

4. Introduction • Apes able to pass invisible displacement tasks. • Monkeys-controversial. • Some studies don’t control for association rules. • Dogs and cats unable to pass. • use association rules instead of true understanding. • Birds also controversial. • Method of training may result in learning association rules.

5. Introduction • Cetaceans and primates both show higher cognitive abilities--like secondary representation. • Dolphins have ability to imitate, mirror self recognition, means-end reasoning, ability to understand symbols.

6. Can dolphins reason about the movements of hidden objects? Introduction

7. Experiment 1—Set Up • Aleta, Delphi, Pandora, Pax, Rainbow, and Tanner • Four males, two females • ages 3-27 years old • All did regular training and public interactions • 3 trash cans • 3 Rubbermaid lids, connected with PVC bar • 1 stuffed toy alligator • 1 opaque PVC cylinder

8. Displacement conditions • Single visible displacement—put object in one bucket only • Double visible displacement—put object in one bucket, then move to a second • Invisible displacement—put object in cylinder, cylinder in bucket, and remove cylinder without object

9. Testing • 1 week per condition • 2 sessions per condition, over 2 consecutive days • 6 choice trials and 3 errorless trials per session • Trial order randomized • Refresher session day before test

10. Training • Object is visible from bucket • One bucket, object is entirely hidden • Introduce object and signal • Intro buckets, then lids • Errorless trials

11. Procedure • Hider calls dolphin • Hide object • Put lid on • Hider gets the Asker • Ask question verbally and with hand signal • Dolphin chooses (with rostrum, or snout) • Removes lid • Correct--pulls object out, blows whistle, reward • Incorrect--asker shows empty bucket and finds correct bucket to show to the dolphin

12. Disruptions Trial aborted if: Redo: Reset if another dolphin comes over If another behavior response or no response, then signal is given again • Dolphin swims away • Touched bucket before signal • Touched something else • If 3 aborted trials in a row, trial is skipped and coded incorrect

13. Coding • Choice is indicated by dolphin touching rostrum (snout) to the bucket, lid, or the displacement cylinder • Video recordings used to • double check results • second experimenter to independently code (100%) reliability

14. Results and Accuracy • Motivation was high • *Rainbow’s data omitted from this trial—still significant results • Overall averages • Single displacement: above chance, P= 0.05 • Double displacement: no success, P= 0.158 • Invisible displacement: no success, P= 0.187

15. Order Effects and Strategies Order Effects Individual Strategies Correct responding First bucket in which object was placed Cylinder, or bucket closest to cylinder Favored bucket– 9 out of 12 selections For 1.-3., 8 out of 12 selections indicate use of a strategy • Single displacement first • typically did better • Perhaps large leap from testing to training?

16. Discussion • Overall average: • Single: pass • Double: fail • Invisible: fail Dolphins do not typically reach for things.

17. Experiment 2—Set Up • AJ, Calusa, Pax*, and Tanner* (Pax and Tanner from Exper. 1 • 1 female, 3 males • ages 4-18 years old • All did regular training and public interactions • Same trash cans and toy alligator • One large lid made from PVC pipe and canvas • Same cylinder

18. Differences Displacement conditions Testing 3 conditions over 3 days Invisible and Transposition counterbalanced Vanishing cylinder test within 5 days after Four trials for each bucket location 12 trials per session 2 sessions per day • Double visible • Invisible • Transposition • Vanishing cylinder—same as 2., but remove cylinder from testing area

19. Training • Pax and Tanner—refresher from Experiment 1 • New subjects given same basic training • Changes to training • No errorless trials • Objects hidden completely • Introduce different lid

20. Procedure Same as Experiment 1, except for: • Incorrect bucket—asker removed object from correct bucket; did not show empty bucket • If dolphin was distracted, trial was aborted, then “timeout,” and trial was put at the end of sessions • 3 skipped trials = end session

21. Results and Accuracy • Motivation was high • Second experimenter coded, 99% reliability • Overall averages • Double displacement: above chance, P= 0.004 • Invisible displacement: no success, P= 0.0464 • transposition: no success, P= 0.760 • No sig. main effect of previous experience, P=0.1888

22. Effects and Strategies Effect of cylinder presence Individual Strategies Same as Experiment 1 plus Selecting moved bucket Only one instance • Dolphins new to the study • Still a chance performance • Experienced dolphins • Much better without cylinder present

23. Discussion • Overall average: • Double: pass • Invisible: fail • Transposition: fail Surprising performance: no containers in natural environment

24. Experiment 3 • Same dolphins as Experiment 2. • Same buckets and lids. • Same procedure for trials. • Toy mouse (small enough to fit in hands).

25. Displacement Conditions • Hand displacement • Drop-first condition • Drop-last condition

26. Results • Dolphins performed above chance only for hand displacement (P < 0.001). • Not drop-first (P=0.215) or drop-last (P=0.058).

27. Discussion • More naturalistic • All dolphins able to complete to pass this invisible displacement condition. • They may be selecting the last bucket the experimenter pays attention to. • Unable to determine bucket with hidden object if experimenter pays attention to more than one bucket.

28. Experiment 4 • Same dolphins, same objects, same procedure. • Same displacement condition as in Experiments 1 & 2 but object is placed in 1st bucket that experimenter visits. • Control for possibility that dolphins are choosing last bucket that trainer touched.

29. Results • Dolphins performed above chance (P=0.011). • Compared to double visible displacement task from Experiment 2. • Visible drop-first and drop-last comparison • Not significant (P=0.89). • Success on visible displacement not due to using a simple response strategy.

30. Overall Results • Visible displacement: pass • Tracking hidden objects: fail • Invisible displacement task: ?? • With hands used instead of cylinder, performance was better

31. Discussion • In past research, “dolphins are proficient in tasks requiring symbolic or secondary representation.” • If Stage 6 object permanence=symbolic/secondary representation, why did the dolphins fail at these tasks?

32. Possible Reason 1--Experiment is not suited to display ability • Different from other permanence studies • Used explicitly trained responses • Perhaps dolphins did not understand task • Only difficulty was with hidden movement; they knew to seek object

33. Possible Reason 2—Perceptual disadvantage • No echolocation • Difficulty perceiving object details • No, because difficulty was when objects were not perceivable

34. Possible Reason 3—Dolphins do not have these abilities • Not likely • Shown evidence of secondary representation in other research

35. Secondary Representation--Support • Imitation • Mirror self-recognition: mark test • Means-ends reasoning • Attributing attention: follow trainers’ gaze • Understanding external representations • Televised images • Yes/no questions

36. Questions Raised Maybe… But… Maybe? Visible drop-first test Removing cylinder did not improve success • Higher memory load? • Distracting movements? • Inhibit preferred responses? Suggestion: test with visually and acoustically opaque occluders instead of containers

37. Summary • Success with visible displacement task, not invisible or transposition • Very puzzling, considering other success • Can do other tasks that are not part of natural behaviors • Perhaps a lack of understanding containers or experience with tracking an object hidden from sight and echolocation • Maybe echolocation helps track hidden objects