Seaweed distribution patterns as revealed by ordination with reference to the Atlantic and southern Oceans

Ordination by Reciprocal Averaging (RA) and Detrended Correspondence Analysis (DECORANA) have been applied to problems of distribution of marine algal floras. The limitations and effectiveness of such methods are discussed and the need to analyse floras as assemblies of species per se rather than being chosen as characterising marine climates is stressed. The openended nature of RA and DECORANA is emphasised as particularly useful in phytogeography with examples from Ascension and Bioko Islands. Paper presented at the XIV International Botanical Congress (Berlin, 24 July–1 August, 1987), Symposium 6-15, “Biogeography of marine benthic algae”.     

Size-Sensitive Perceptual Representations Underlie Visual and Haptic Object Recognition

A variety of similarities between visual and haptic object recognition suggests that the two modalities may share common representations. However, it is unclear whether such common representations preserve low-level perceptual features or whether transfer between vision and haptics is mediated by high-level, abstract representations. Two experiments used a sequential shape-matching task to examine the effects of size changes on unimodal and crossmodal visual and haptic object recognition. Participants felt or saw 3D plastic models of familiar objects. The two objects presented on a trial were either the same size or different sizes and were the same shape or different but similar shapes. Participants were told to ignore size changes and to match on shape alone. In Experiment 1, size changes on same-shape trials impaired performance similarly for both visual-to-visual and haptic-to-haptic shape matching. In Experiment 2, size changes impaired performance on both visual-to-haptic and haptic-to-visual shape matching and there was no interaction between the cost of size changes and direction of transfer. Together the unimodal and crossmodal matching results suggest that the same, size-specific perceptual representations underlie both visual and haptic object recognition, and indicate that crossmodal memory for objects must be at least partly based on common perceptual representations.