'An Investigation of Habituation in the Jellyfish, Aurelia aurita' by Mary C Johnson and Karl L Wuensch (Behavioral and Neural Biology, vol 61, 1994) reports on a series of experiments designed to discover how jellyfish react to a repeated stimulus.
'Habituation,' they begin, 'is considered by many to be the most basic, ubiquitous type of learning.' If you keep tickling an animal, it will get used to it and stop giggling. Such habituation has been shown to hold for complex organisms, but is less well established among creatures without a brain or centralised nervous system.
Muscular fatigue and sensory adaptation may provide some explanation for altered response, but there is also clear evidence of behavioural adaptation in some relatively primitive life forms. Nobody, however, had yet tried jellyfish. In terms of co-ordinated behaviour, there are two things jellyfish do - eat and protect themselves. Eating involves co-ordination between tentacles and mouth; protection involves a contraction of tentacles and folding them over the mouth. The experiments concentrated on the contractile response to see whether such cringing diminished on repeated application of a tactile stimulus.
Using three standard stimuli - stream, probe and shake - the experimenters squirted water at the jellyfish, or gently prodded it, or agitated its bowl. The stimulus was repeated at regular intervals, and the reactions observed. 'One polyp was dropped because it was totally unresponsive'.
The experiments confirmed that as long as the intervals between separate applications of the stimuli are kept short, the jellyfish significantly decrease in responsiveness. However, if they suddenly changed the type of stimulus, a significant increase in response was measured, thus confirming that habituation was occurring, rather than muscular fatigue. The report concludes: 'These results open the door to further investigation of habituation in the jellyfish'.
As experimental animals, jellyfish are rather limited in their communication skills, and as for their abilities to process semantic relations and syntactic information, the less said the better. Dolphins, however, are worth talking to.
In 'Responses to Anomalous Gestural Sequences by a Language- Trained Dolphin: Evidence for Processing of Semantic Relations and Syntactic Information', (Journal of Experimental Psychology: General, vol 122, 1993) Louis M Herman, Stan A Kuczaj II and Mark D Holder investigated what happened if you talked nonsense to a bottle- nosed dolphin.
Previous studies had used two dolphins, named Akeakamai and Phoenix. Akeakamai had been trained to understand a language of gestures, while Phoenix responded to electronically-generated whistling sounds. In each case, distinct gestures or whistles corresponded to objects in the tank, actions relating to the objects, relationships between objects or modifiers of place or action.
Syntactic rules enabled the generation of simple sentences to which the dolphin could respond. So 'Right Frisbee Over' indicated that the dolphin was to jump over the frisbee on its right; 'Left Hoop Pipe Fetch' instructed her to take the pipe on her left to a hoop. The importance of word order is seen by comparing 'Surfboard Person Fetch' (take person to surfboard) with 'Person Surfboard Fetch' (take surfboard to person).
Previous research had shown that dolphins could pick up the ideas of the language and follow instructions they had never heard before, as long as the individual words and syntax were familiar to them. But what happens if you tell them to 'Over Frisbee' instead of 'Frisbee Over'. Would they still jump?
For the new experiments, Akeakamai, now 13 and very experienced in language use, was placed in a tank with Ball, Frisbee, Basket, Surfboard, Pipe and Hoop, a person (Person) sitting on the tank wall, a hose (Water) pouring water into the tank, an underwater speaker (Speaker), four windows (Window), and the other dolphin (Phoenix). It was given a series of meaningful instructions with the occasional thing such as 'Water Phoenix Fetch Over', which makes no sense at all, thrown in to confuse it.
The results showed that while Akeakamai was likely to reject anomalous sequences, it always acted on semantically correct instructions. However, if the anomalous sequence contained a meaningful instruction as a subset, it was liable to respond to that part, even if they consisted of gestures that were not sequentially adjacent. 'The results show the importance of both semantic properties and semantic relations of the referents of the gestures and of syntactic (ordering) constraints in the dolphin's interpretations of the anomalies.'
No study, as far as we know, has yet been made into the personalities of people who tickle jellyfish or talk gibberish to dolphins, but Neil A Douse and I C McManus have made an equally important contribution to knowledge in 'The Personality of Fantasy Game Players' in the British Journal of Psychology, vol 84, 1993. They selected a group of 52 people who played fantasy role-playing games (FRPGs) by mail, using a number of personality measures to compare them with a control group of students and hospital patients.
The results showed that players of FRPGs show clear personality differences from the controls 'although the differences are not as extreme as some stereotypical descriptions might have suggested', which seems to deny the mandatory anorak hypothesis. 'FRPG players are significantly more introverted, less feminine, less androgynous and show less empathic concern than controls'. Most players are male, which, together with their lack of empathy, confirms earlier accounts of their habit of 'forming emotional relations with objects and also treating people as objects'.
Whether they become habituated to tickling is still an open question.