Radial-tangential anisotropy of crowding in the early visual areas

Crowding, the inability to recognize an individual object in clutter (Bouma H. Nature 226: 177–178, 1970), is considered a major impediment to object recognition in peripheral vision. Despite its significance, the cortical loci of crowding are not well understood. In particular, the role of the primary visual cortex (V1) remains unclear. Here we utilize a diagnostic feature of crowding to identify the earliest cortical locus of crowding. Controlling for other factors, radially arranged flankers induce more crowding than tangentially arranged ones (Toet A, Levi DM. Vision Res 32: 1349–1357, 1992). We used functional magnetic resonance imaging (fMRI) to measure the change in mean blood oxygenation level-dependent (BOLD) response due to the addition of a middle letter between a pair of radially or tangentially arranged flankers. Consistent with the previous finding that crowding is associated with a reduced BOLD response [Millin R, Arman AC, Chung ST, Tjan BS. Cereb Cortex (July 5, 2013). doi:10.1093/cercor/bht159], we found that the BOLD signal evoked by the middle letter depended on the arrangement of the flankers: less BOLD response was associated with adding the middle letter between radially arranged flankers compared with adding it between tangentially arranged flankers. This anisotropy in BOLD response was present as early as V1 and remained significant in downstream areas. The effect was observed while subjects' attention was diverted away from the testing stimuli. Contrast detection threshold for the middle letter was unaffected by flanker arrangement, ruling out surround suppression of contrast response as a major factor in the observed BOLD anisotropy. Our findings support the view that V1 contributes to crowding.

A Word-Superiority Effect in the Presence of Foveal Load

Foveal stimuli have been shown to disrupt visual information processing in the parafovea and periphery by their mere presence. In the present study, 6 subjects were presented letter triads 3.58° to the right or left of the point of fixation. At the same time, a single letter was presented at the point of fixation that was either the same as the middle letter in the triad or different from any of the triad letters. On other trials, no letter was presented at the point of fixation. Analysis indicated a word superiority effect when a foveal letter was presented that was the same as the letter in the triad. Performance between words and nonwords did not differ significantly when the foveal letter was different or absent. It was concluded that the mere presence of foveal load alone is not disruptive to performance. Depending on the visual context of the target to be reported, the presence of a foveal stimulus may improve performance.

Response-Set Size and Paired-Associate Learning

4 groups of 15 students each learned a single unmixed list of 13 pairs for five anticipation trials followed by a free-recall test. The lists contained pairs of nonsense syllables that rhymed, changed middle letter, reversed the letter order, or were unrelated. All lists involving rules were superior to the list of unrelated pairs. In order of increasing effectiveness the rules were rhyming, middle-letter change, letter reversal. Performance was inversely related to response-set size. The more restrictive rules resulted in increased free recall of the pairs. Results supported the hypothesis that rules are beneficial to the extent that they reduce response-set size.

Role of Rules in Paired-Associate Learning

14 students in each of four groups learned a single unmixed list of 19 CVC pairs for 12 anticipation trials followed by a free recall of the pairs. In three of the four lists a single rule applied to all of the pairs. The rule was that the words in each pair changed first letter (rhymed), changed middle letter, or changed last letter. A fourth list contained only pairs of unrelated words. Mean number of correct anticipations per trial showed rhyming and end-change rules to be equally beneficial, although not as effective as the middle-change rule. Free recall of the pairs showed no differences among lists. Results were interpreted as supporting the hypothesis that rules facilitate retrieval by restricting the number of responses to be considered for each stimulus.

Children's Learning of Words as a Function of Minimum Contrasts in Variable Letter Positions

Presents results of an experimental task which measured children's learning of CVC words when minimum contrasts were employed in first, middle, and last letter positions ( e.g., tin, win vs. pan, pen vs. pit, pig). Subjects were 84 kindergarten and first grade pupils who knew the alphabet but who had not yet learned to read. The visual and oral task provided measures of transfer, recognition, recall, delayed recognition, and delayed recall. For the sexes separately and combined, first letter position contrasts (rhyming words) were superior to letter contrasts in the middle or last letter positions; middle letter position contrasts were least effective. Last letter position contrasts were more effective for females than males. The results suggest that the teaching of rhyming words is the most efficient initial presentation of CVC words for beginning readers.

The Origin and Date of the ‘Sator’ Word-Square

The recent extensive article on this subject by the distinguished French Scholar Dr. Jérome Carcopino provides an opportunity to return to a subject which I have already discussed in a paper published shortly before the War. Since its publication fresh evidence has come to light which may be thought to bear upon the subject, and various explanations of the origin of the square have been put forward which seem to invite comment. The exhaustive article of Fr. de Jerphanion, which is largely summarized by Carcopino, makes necessary only the briefest sketch of the development of our knowledge of the square. In its later form (beginning with Sator, fig. 2) it can be traced in a more or less complete form from the sixth century to modern times over an area extending from France to Ethiopia, Nubia, and even to South America, where its prophylactic virtues were accepted in the nineteenth century. The discovery of its earlier form (beginning with Rotas, fig. 1) incised on Roman wall-piaster at Cirencester in 1868 caused little interest, and it remained almost exclusively a matter for the medievalist for many years. In 1926 it was observed by Grosser that twenty-one of the letters of the square were made up of the word ‘Paternoster’ twice over (but necessarily arranged as a cross since the N, the middle letter, appears only once) and that the remaining four letters are two A's and two O's (fig. 4).