Crowding effect in lexical and sublexical recognition

We studied the crowding effect in a letter strings identification task by using progressive de-masking. In this degraded stimulus presentation procedures, the letter string emerges from the mask, with the advantage of providing response time as well as accuracy measurements. Stimuli were familiar words or pronounceable nonwords, and spacing between letters was manipulated. We used standard letter and decreased letter spacing (1.03×letter length). The letter string was centrally displayed and it subtended an angle of 5 deg (for the longest strings). Our results show that the identification of decreased spaced strings was slower than normally spaced strings (crowding effect). More importantly, decreasing distance between letters impaired more nonwords than words identification, showing a possible top-down modulation on crowding effect. Since sublexical identification and decoding are crucial for reading development, an increased crowding could be an important factor underling reading difficulties typically shown in dyslexic children.