Comment on recognition and confusion of the lowercase alphabet.

Abstract

In a recent issue of this journal, Geyer (1977) presents an analysis of a full alphabet matrix for lowercase letters foveal vision. Geyer indicates previous data for the lowercase alphabet (Bouma, 1971) are inconclusive. Bouma presents two experiments which the procedures used to control average correct performance differ substantially. In one experiment, letters are presented foveally, correct performance being limited to 50% by manipulating viewing distance. The second experiment manipulated the degree of eccentric exposure along the horizontal meridian, to achieve the desired level of performance. forced-choice procedure was used the latter experiment but not the former, and the letter y was omitted from the stimulus set the nonfoveal condition. Bouma concluded on subjective grounds the foveal and nonfoveal matrices were sufficiently similar, and thus averaged the results across the foveal and nonfoveal matrices subsequent analyses. Geyer (1977) suggests the comparability of processing between foveal and nonfoveal regions, based on identification performance, must be considered an empirical question. Geyer attempts to answer this question by comparing the matrix reported by Bouma (1971) for eccentric vision with the foveal matrix presented Geyer (1977). He makes this comparison on the basis of the sum square deviation of (1) the foveal and nonfoveal matrices (2.08), and (2) the foveal matrix and a dummy matrix (1.79), uniformly composed of 0.5 along main-diagonal cells and 0.02 elsewhere (Geyer, 1977, p, 489). The use of this technique the evaluation of matrix data is not unprecedented. Townsend (1971a, 1971b) suggests the sum of squared deviations as an index of the accuracy of fit between predicted and empirical matrices. However, caution must be exercised the interpretation of this index. Geyer assumes this difference to be a significant one. The statistical basis for this assumption is not entirely clear. How large a difference is significant? Without a knowledge of the underlying distribution, such an inferential statement cannot be made. Geyer concludes the difference between sum square deviations may be regarded as evidence support of the notion that foveal and nonfoveal recognition processes differ qualitatively (p. 489). This statement is somewhat premature and may overstep the facts. No mention is made regarding the manner which the missing data from Bouma's non foveal matrix are treated. If the row for y (y was not presented) Bouma's 25 by 26 matrix is replaced by inserting .00 all of the cells, then the sum square deviation is artificially inflated. Some mention of the way which this problem was dealt with is essential to the interpretation of the comparison. Over and above the statistical question, there is perhaps a more fundamental criticism to be considered. The stimuli Geyer's study were from the Tactype Futura demi 5424 alphabet, a font without serifs. Geyer states this type style was chosen in order to minimize the influence of any particular type style idiosyncracy (p. 488). Bouma (1971) used letters of the typeface Courier 10 (IBM), a font which has pronounced serifs (p. 460). An inspection of the two type styles reveals there are considerable differences structure between corresponding letter pairs. few examples will serve to illustrate the potentialconfound inherent the comparison of different type styles. The letter A Tactype Futura demi 5424 (a) shares very few features common with the same letter Courier 10 (a) type. The similarity of Geyer's ( a) to the letter ( 0 ) is reflected the 14010 response between these two when (a) is the stimulus. Contrast with this the lack of reported by Bouma, between the same two letters (a) and (0) when (a) is the stimulus (1010). more compelling example is seen the 31010 reported by Bouma when (g) is the stimulus and (q) the response. The same occurs only 7010 of the time for Geyer's (g) and (q ). The difference structure and of itself, between these pairs, might be an important contributing factor to the differences between the foveal and nonfoveal matrices. It seems questionable whether the differences reported by Geyer (1977) can be unequivocally attributed to differences information processing between different retinal loci. It may be unreasonable to assume differences type style can be disregarded this way. Maddox, Burnette, and Gutmann (1977) present data for uppercase dot matrix letters, which indicate letter style may be an important variable altering the of confusions. Further, research presented by Fisher, Monty, and Glucksberg (1969) suggests comparison across data derived from different procedures may not be valid. The comparison made by Geyer (1977) rests on the assumption a basic pattern of confusion exists between the lowercase letters of the