Figure 2.

Using Representational Similarity Analysis to identify the influence of specific representational types on the recognition of letters viewed in the Upright Gridfont. (A) The first column depicts the types of letter representations potentially active in response to viewing a and G in the Upright Gridfont. (B) The second column depicts an approximation of the representational content of Upright Gridfont a and G for each representational type. Computed Stimulus-Shape similarity is estimated with rotated Gridfont letters. Rotation maintains pairwise visual-spatial similarity while minimizing the identifiability of the rotated letters, thereby, limiting the influence of the other representational types on letter recognition. Allograph similarity is estimated from the similarity structure of a more typical font. Symbolic Letter identities encode font and case-invariant letter identity. Letter-name similarity is estimated from the phonetic features that compose the phonemes of the letter-names. Motoric similarity is estimated from hypothesized motor plans. (C) The third column depicts matrices of pairwise similarity estimates for each type of representation (pRSMs), characterizing the predicted similarity structures at each level of representation in response to pairs of the Upright Gridfont letters. (D) Column 4 depicts a set of similarity responses (e.g., derived from judgments or same/different RTs or accuracy) elicited in response to letter pairs (the oRSM). These similarity responses are tested for the unique influence of each of the 5 types of letter representations by running a linear mixed-effects model (LMEM) in which the 5 pRSMs simultaneously predict the responses to the Upright Gridfont letter-pairs.