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1.  Single-digit Arabic numbers do not automatically activate magnitude representations in adults or in children: Evidence from the symbolic same–different task☆ 
Acta Psychologica  2013;144(3):488-498.
We investigated whether the mere presentation of single-digit Arabic numbers activates their magnitude representations using a visually-presented symbolic same–different task for 20 adults and 15 children. Participants saw two single-digit Arabic numbers on a screen and judged whether the numbers were the same or different. We examined whether reaction time in this task was primarily driven by (objective or subjective) perceptual similarity, or by the numerical difference between the two digits. We reasoned that, if Arabic numbers automatically activate magnitude representations, a numerical function would best predict reaction time; but if Arabic numbers do not automatically activate magnitude representations, a perceptual function would best predict reaction time. Linear regressions revealed that a perceptual function, specifically, subjective visual similarity, was the best and only significant predictor of reaction time in adults and in children. These data strongly suggest that, in this task, single-digit Arabic numbers do not necessarily automatically activate magnitude representations in adults or in children. As the first study to date to explicitly study the developmental importance of perceptual factors in the symbolic same–different task, we found no significant differences between adults and children in their reliance on perceptual information in this task. Based on our findings, we propose that visual properties may play a key role in symbolic number judgements.
•Single-digit Arabic numbers do not automatically activate magnitude representations.•This is true for both adults and children.•Subjective visual properties may play a key role in symbolic number judgments.
PMCID: PMC3842502  PMID: 24076332
Symbolic numbers; Numerical cognition; Automaticity; Magnitude representations; Same–different task
2.  The link between mental rotation ability and basic numerical representations 
Acta Psychologica  2013;144(2):324-331.
Mental rotation and number representation have both been studied widely, but although mental rotation has been linked to higher-level mathematical skills, to date it has not been shown whether mental rotation ability is linked to the most basic mental representation and processing of numbers. To investigate the possible connection between mental rotation abilities and numerical representation, 43 participants completed four tasks: 1) a standard pen-and-paper mental rotation task; 2) a multi-digit number magnitude comparison task assessing the compatibility effect, which indicates separate processing of decade and unit digits; 3) a number-line mapping task, which measures precision of number magnitude representation; and 4) a random number generation task, which yields measures both of executive control and of spatial number representations. Results show that mental rotation ability correlated significantly with both size of the compatibility effect and with number mapping accuracy, but not with any measures from the random number generation task. Together, these results suggest that higher mental rotation abilities are linked to more developed number representation, and also provide further evidence for the connection between spatial and numerical abilities.
•We show a link between mental rotation ability (MRA) and numerical representation.•MRA correlated with a measure of holding concurrent multiple number representations.•MRA correlated with a measure of number representation precision (number line task).•MRA did not correlate with an executive control task (random number generation).•These findings strengthen the link observed between spatial and numerical abilities.
PMCID: PMC3793858  PMID: 23933002
Mental rotation; Numerical representation; Compatibility effect; Numerical cognition; Number line; Spatial abilities
3.  Alphabetic letter identification: Effects of perceivability, similarity, and bias☆ 
Acta Psychologica  2011;139(1):19-37.
The legibility of the letters in the Latin alphabet has been measured numerous times since the beginning of experimental psychology. To identify the theoretical mechanisms attributed to letter identification, we report a comprehensive review of literature, spanning more than a century. This review revealed that identification accuracy has frequently been attributed to a subset of three common sources: perceivability, bias, and similarity. However, simultaneous estimates of these values have rarely (if ever) been performed. We present the results of two new experiments which allow for the simultaneous estimation of these factors, and examine how the shape of a visual mask impacts each of them, as inferred through a new statistical model. Results showed that the shape and identity of the mask impacted the inferred perceivability, bias, and similarity space of a letter set, but that there were aspects of similarity that were robust to the choice of mask. The results illustrate how the psychological concepts of perceivability, bias, and similarity can be estimated simultaneously, and how each make powerful contributions to visual letter identification.
PMCID: PMC3271710  PMID: 22036587
Letter similarity; Choice theory
4.  Causal conditionals and counterfactuals 
Acta Psychologica  2012;141(1):54-66.
Causal counterfactuals e.g., ‘if the ignition key had been turned then the car would have started’ and causal conditionals e.g., ‘if the ignition key was turned then the car started’ are understood by thinking about multiple possibilities of different sorts, as shown in six experiments using converging evidence from three different types of measures. Experiments 1a and 1b showed that conditionals that comprise enabling causes, e.g., ‘if the ignition key was turned then the car started’ primed people to read quickly conjunctions referring to the possibility of the enabler occurring without the outcome, e.g., ‘the ignition key was turned and the car did not start’. Experiments 2a and 2b showed that people paraphrased causal conditionals by using causal or temporal connectives (because, when), whereas they paraphrased causal counterfactuals by using subjunctive constructions (had…would have). Experiments 3a and 3b showed that people made different inferences from counterfactuals presented with enabling conditions compared to none. The implications of the results for alternative theories of conditionals are discussed.
► Causal counterfactuals understood by envisaging different sorts of possibilities. ► Causal counterfactuals are paraphrased differently compared to causal conditionals. ► People make different inferences from counterfactuals in the context of a story.
PMCID: PMC3657137  PMID: 22858874
Conditional reasoning; Counterfactuals; Causality; Enablers; Mental models
5.  Can 9.5-month-old infants attribute to an agent a disposition to perform a particular action on objects? 
Acta Psychologica  2006;124(1):79-105.
The present research examined whether 9.5-month-old infants can attribute to an agent a disposition to perform a particular action on objects, and can then use this disposition to predict which of two new objects—one that can be used to perform the action and one that cannot—the agent is likely to reach for next. The infants first received familiarization trials in which they watched an agent slide either three (Experiments 1 and 3) or six (Experiment 2) different objects forward and backward on an apparatus floor. During test, the infants saw two new identical objects placed side by side: one stood inside a short frame that left little room for sliding, and the other stood inside a longer frame that left ample room for sliding. The infants who saw the agent slide six different objects attributed to her a disposition to slide objects: they expected her to select the “slidable” as opposed to the “unslidable” test object, and they looked reliably longer when she did not. In contrast, the infants who saw the agent slide only three different objects looked about equally when she selected either test object. These results add to recent evidence that infants in the first year of life can attribute dispositions to agents, and can use these dispositions to help predict agents’ actions in new contexts.
PMCID: PMC3357326  PMID: 17092476
Infant cognition; Disposition; Action comprehension; Psychological reasoning
6.  15-month-old infants detect violations in pretend scenarios 
Acta Psychologica  2006;124(1):106-128.
Are 15-month-old infants able to detect a violation in the consistency of an event sequence that involves pretense? In Experiment 1, infants detected a violation when an actor pretended to pour liquid into one cup and then pretended to drink from another cup. In Experiment 2, infants no longer detected a violation when the cups were replaced with objects not typically used in the context of drinking actions, either shoes or tubes. Experiment 3 showed that infants’ difficulty in Experiment 2 was not due to the use of atypical objects per se, but arose from the novelty of seeing an actor appearing to drink from these objects. After receiving a single familiarization trial in which they observed the actor pretend to drink from either a shoe or a tube, infants now detected a violation when the actor pretended to pour into and to drink from different shoes or tubes. Thus, at an age (or just before the age) when infants are beginning to engage in pretend play, they are able to show comprehension of at least one aspect of pretense in a violation-of-expectation task: specifically, they are able to detect violations in the consistency of pretend action sequences.
PMCID: PMC3351386  PMID: 17107649
Cognitive development; Infancy; Pretense comprehension; Theory of mind
7.  Language can mediate eye movement control within 100 milliseconds, regardless of whether there is anything to move the eyes to 
Acta Psychologica  2011;137(2):190-200.
The delay between the signal to move the eyes, and the execution of the corresponding eye movement, is variable, and skewed; with an early peak followed by a considerable tail. This skewed distribution renders the answer to the question “What is the delay between language input and saccade execution?” problematic; for a given task, there is no single number, only a distribution of numbers. Here, two previously published studies are reanalysed, whose designs enable us to answer, instead, the question: How long does it take, as the language unfolds, for the oculomotor system to demonstrate sensitivity to the distinction between “signal” (eye movements due to the unfolding language) and “noise” (eye movements due to extraneous factors)? In two studies, participants heard either ‘the man…’ or ‘the girl…’, and the distribution of launch times towards the concurrently, or previously, depicted man in response to these two inputs was calculated. In both cases, the earliest discrimination between signal and noise occurred at around 100 ms. This rapid interplay between language and oculomotor control is most likely due to cancellation of about-to-be executed saccades towards objects (or their episodic trace) that mismatch the earliest phonological moments of the unfolding word.
PMCID: PMC3118831  PMID: 20965479
Oculomotor control; Saccades; Double-step paradigm; Language-mediated eye movements; Visual world paradigm
8.  Recognition memory for pictorial material in subclinical depression 
Acta Psychologica  2010;135(3):293-301.
Depression has been associated with impaired recollection of episodic details in tests of recognition memory that use verbal material. In two experiments, the remember/know procedure was employed to investigate the effects of dysphoric mood on recognition memory for pictorial materials that may not be subject to the same processing limitations found for verbal materials in depression. In Experiment 1, where the recognition test took place two weeks after encoding, subclinically depressed participants reported fewer know judgements which were likely to be at least partly due to a remember-to-know shift. Although pictures were accompanied by negative or neutral captions at encoding, no effect of captions on recognition memory was observed. In Experiment 2, where the recognition test occurred soon after viewing the pictures, subclinically depressed participants reported fewer remember judgements. All participants reported more remember judgements for pictures of emotionally negative content than pictures of neutral content. Together, these findings demonstrate that recognition memory for pictorial stimuli is compromised in dysphoric individuals in a way that is consistent with a recollection deficit for episodic detail and also reminiscent of that previously reported for verbal materials. These findings contribute to our developing understanding of how mood and memory interact.
PMCID: PMC2994638  PMID: 20728865
Depression; Memory; Emotion; Recollection; Familiarity

Results 1-8 (8)