What various kinds of errors tell us about lateral masking effects

Error analyses were conducted to study processes underlying lateral masking effects. Location errors (i.e., confusions with a flanking letter) occurred at a rate higher than chance, and they increased with increasing eccentricity and with decreasing spacing. In longer strings, confusions with a flanker directly adjacent to the target (which is itself laterally masked) were more frequent than with a far flanker, and these confusions also increased with increasing eccentricity and with decreasing spacing indicating that identification of the letter's form is not necessarily disturbed by adjacent characters. This was confirmed in a whole report task, where there was better recognition performance for the central letter than in partial report. Whereas in partial report, the left flanker was more often confused with the target than the right one, in whole report, the left-most letter was recognized best. The data provide evidence that positional uncertainty contributes to lateral masking effects, and that a substantial portion of positional uncertainty occurs after having identified the letter's forms.