Unsaid thoughts: Thinking in the absence of verbal logical connectives.

Combining two thoughts into a compound mental representation is a central feature of our verbal and non-verbal logical abilities. We here approach this issue by focusing on the contingency that while natural languages have typically lexicalised only two of the possible 16 binary connectives from formal logic to express compound thoughts-namely, the coordinators and and or-some of the remainder appear to be entertainable in a non-verbal, conceptual representational system-a language of thought-and this suggests a theoretical split between the "lexicalisation" of the connectives and the "learnability" of invented words corresponding to unlexicalised connectives. In a visual world experiment aimed at tracking comprehension-related as well as reasoning-related aspects of the capacity to represent compound thoughts, we found that participants are capable of learning and interpreting a made-up word standing for logic's NAND operator, a result that indicates that unlexicalised logical connectives are not only conceptually available, but can also be mapped onto new function words, as in the case of coordinators, or connectives, a class of words that do not usually admit new coinages.

Parsing for Position.

Monitoring tasks have long been employed in psycholinguistics, and the end-of-clause effect is possibly the better-known result of using this technique in the study of parsing. Recent results with the tone-monitoring task suggest that tone position modulates cognitive load, as reflected in reaction times (RTs): the earlier the tone appears in a sentence, the longer the RTs. In this study, we show that verb position is also an important factor. In particular, changing the time/location at which verb-noun(s) dependencies are computed during the processing of a sentence has a clear effect on cognitive load and, as a result, on the resources that can be devoted to monitoring and responding to a tone. This study is based on two pieces of evidence. We first report the acceptability ratings of six word orders in Spanish and then present monitoring data with three of these different word orders. Our results suggest that RTs tend to be longer if the verb is yet to be processed, pointing to the centrality of a sentence's main verb in parsing in general.

Disentangling perceptual and psycholinguistic factors in syntactic processing: Tone monitoring via ERPs.

Franco, Gaillard, Cleeremans, and Destrebecqz (Behavior Research Methods, 47, 1393-1403, 2015), in a study on statistical learning employing the click-detection paradigm, conclude that more needs to be known about how this paradigm interacts with statistical learning and speech perception. Past results with this monitoring technique have pointed to an end-of-clause effect in parsing-a structural effect-but we here show that the issues are a bit more nuanced. Firstly, we report two Experiments (1a and 1b), which show that reaction times (RTs) are affected by two factors: (a) processing load, resulting in a tendency for RTs to decrease across a sentence, and (b) a perceptual effect which adds to this tendency and moreover helps neutralize differences between sentences with slightly different structures. These two factors are then successfully discriminated by registering event-related brain potentials (ERPs) during a monitoring task, with Experiment 2 establishing that the amplitudes of the N1 and P3 components-the first associated with temporal uncertainty, the second with processing load in dual tasks-correlate with RTs. Finally, Experiment 3 behaviorally segregates the two factors by placing the last tone at the end of sentences, activating a wrap-up operation and thereby both disrupting the decreasing tendency and highlighting structural effects. Our overall results suggest that much care needs to be employed in designing click-detection tasks if structural effects are sought, and some of the now-classic data need to be reconsidered.

Probing recursion.

The experimental probing of recursion in human performance is faced with non-trivial problems. Here, I analyse three case studies from the literature and argue that they tell us little about the underlying mental processes at play within each of these domains: (a) the question of whether experimental participants employ recursive rules in parsing artificial strings of nonsense syllables; (b) the role of self-embedded structures in reasoning and general cognition; and (c) the reputed connection between structural features of a given object and the corresponding, recursive rules needed to represent/generate it. I then outline what a recursive process would actually look like and how one could go about probing its presence in human behaviour, concluding, however, that recursive processes in performance are very unlikely, at least as far as fast, mandatory, and automatic modular processes are concerned.