Disentangling perceptual uncertainty and incrementality in syntactic processing: Click monitoring via ERPs David J. Lobina, Josep Demestre & Jos´ e E. Garc´ ıa-Albea Abstract Past results with the click monitoring technique have pointed to an end- of-clause effect, but we here show that the issues at hand are a bit more nuanced —and more interesting. Firstly, by employing two types of simple, subject-verb-object sentences and three click positions, we report two exper- iments (1a and 1b) which show that reaction times (RTs) are affected by two factors: a) a strong perceptual effect we dub the position effect, involved in monitoring tasks in general, and which neutralises structural differences across experimental conditions; and b) the incremental processing the parser carries out means that more resources to respond to a tone are released as a sentence is presented, as evidenced in the tendency of RTs to decrease across a sentence. These two factors are then successfully discriminated and recor- ded by registering event-related brain potentials (ERPs) in a click monitoring task, with experiment 2 establishing that the amplitudes of the N1 and P3 components —the first component is associated with temporal uncertainty in perception and the second with processing effort in dual tasks— correlate with the RT pattern unearthed in the previous two experiments. In addition, it is argued that the P3 component is a useful metric with which to measure the cognitive load exercised by the syntactic parser when employing a dual-task experimental setting, and we believe this is the first time it is so employed in psycholinguistics. In experiment 3, we segregate these two factors by placing the last tone on the penultimate syllable of the experimental sentences, with the result that RTs to that position are found to increase greatly with respect to the immediately preceding tone, confirming a wrap-up effect (rather than an end-of-clause effect) in speech perception, and thereby both disrupting the position effect and highlighting purely structural factors. Finally, past results with the click-detection paradigm are reconsidered in terms of our data. Keywords: Click monitoring; ERPs; Processing load; Position effect; Wrap-up. 1 The Past Click monitoring originated from the click-location paradigm, the latter an experi- mental technique first employed in the mid 1960s as a way to show that the clausal 1