The behavioural response of the whelk Buccinum undatum L. to its predator, the seastar Leptasterias polaris Miiller, was exam~ned by quantifying the whelk's response to liv~ng seastars or water which had been exposed to a seastar, and to saponins extracted from seastars. Whelks detect the seastar by water-borne substances Contact with seastars or water which had contained the seastar for a prolonged period (3 h) usually provoked contortions. The whelk showed no response to the nonpredatory seastar Henricia sp. Saponlns extracted from the aboral surface, oral surface, cardlac stomach, and pyloric caecum of L. polaris all provoked defensive reactions which become stronger with increasing saponin concentration. The weakest response was from extracts from the pyloric caecum. In contrast to sexually mature whelks measuring >7 cm in shell length, smaller immature whelks less frequently underwent contortions in response to L. polaris; rather, they rapidly attached to the substratum and fled. The development of a strong and reliable escape response (contortions) by large whelks probably permits them to associate more closely with large L. polaris and thus profit from abundant bivalve prey in deeper sediment bottom areas.

Previous research indicates that the extent of progress made by children with phonological disorders depends upon the nature of the word pairs contrasted in therapy. For example, phonemes that differ maximally in terms of place, manner, voicing and sound class (e.g., fan -man) in comparison to therapy where the word pairs presented differ minimally (e.g., fan -van). To investigate the implications of target selection within a typical clinical context (as opposed to a rigorous research setting) eight speech-language pathologists implemented intervention with appropriate children from their caseloads. Nineteen children each received 6 hours of therapy over one school term. They were randomly allocated to two groups. One group (of nine children) received intervention based on a traditional minimal pair approach, targeting homonymy as well as distinctive feature contrast. The other group (ten children) received intervention targeting contrasts differing across a range of distinctive features. Children made considerable progress in therapy in terms of speech accuracy and number of error patterns suppressed. However, there was no difference between the progress of the two groups. Followup assessment of 14 of the 19 children indicated maintenance of progress by both groups. Reasons for the lack of difference between the groups in the current study are considered and clinical implications are drawn.

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Interview

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