Tommaso Mastropasqua

Location transfer of perceptual learning: Passive stimulation and double training

Specificity has always been considered one of the hallmarks of perceptual learning, suggesting that performance improvement would reflect changes at early stages of visual analyses (e.g., V1). More recently, however, this view has been challenged by studies documenting complete transfer of learning among different spatial locations or stimulus orientations when a double-training procedure is adopted. Here, we further investigate the conditions under which transfer of visual perceptual learning takes place, confirming that the passive stimulation at the transfer location seems to be insufficient to overcome learning specificity. By contrast, learning transfer is complete when performing a secondary task at the transfer location. Interestingly, (i) transfer emerges when the primary and secondary tasks are intermingled on a trial-by-trial basis, and (ii) the effects of learning generalization appear to be reciprocal, namely the primary task also serves to enable transfer of the secondary task. However, if the secondary task is not performed for a sufficient number of trials, then transfer is not enabled. Overall, the results lend support to the recent view that task-relevant perceptual learning may involve high-level stages of visual analyses.

Broadening the study of inductive reasoning: Confirmation judgments with uncertain evidence

Although evidence in real life is often uncertain, the psychology of inductive reasoning has, so far, been confined to certain evidence. The present study extends previous research by investigating whether people properly estimate the impact of uncertain evidence on a given hypothesis. Two experiments are reported, in which the uncertainty of evidence is explicitly (by means of numerical values) versus implicitly (by means of ambiguous pictures) manipulated. The results show that people’s judgments are highly correlated with those predicted by normatively sound Bayesian measures of impact. This sensitivity to the degree of evidential uncertainty supports the centrality of inductive reasoning in cognition and opens the path to the study of this issue in more naturalistic settings.

Learning of monocular information facilitates breakthrough to awareness during interocular suppression

Continuous flash suppression (CFS) is a potent method of inducing binocular rivalry, wherein a rapid succession of high-contrast images presented to one eye effectively blocks from awareness a low-contrast image presented to the other eye. Here we addressed whether the contents of the suppressed image can break through to awareness with extended CFS exposure. On 2/3 of the trials, we presented a faint bar (the target) to the nondominant eye while a high-contrast flickering Mondrian (the mask) was displayed to the dominant eye. Participants were first asked to report whether the target had broken through the CFS mask. Furthermore, on target-present trials, the participants were then asked to guess whether the target had appeared above or below the fixation point. In Experiment 1, the target was presented with a fixed orientation for four blocks of trials, whereas in the fifth block, the target could also have the orthogonal orientation. In Experiment 2, the target was always presented with a fixed orientation, but in the fifth block, unbeknownst to participants, the target and the mask were swapped across the eyes. We found that awareness of the target rapidly improved with training in both experiments. However, whereas Experiment 1 revealed that the improvement largely generalized across stimulus orientations, Experiment 2 showed that the effect of practice was eye-specific. The results suggest that increased breakthrough with training was due to a monocular form of learning. Finally, a control experiment was conducted to exclude the possibility that the monocular learning we reported could have been due to sensory adaptation caused by the masks.

Attention is necessary for subliminal instrumental conditioning.

The capacity of humans and other animals to provide appropriate responses to stimuli anticipating motivationally significant events is exemplified by instrumental conditioning. Interestingly, in humans instrumental conditioning can occur also for subliminal outcome-predicting stimuli. However, it remains unclear whether attention is necessary for subliminal instrumental conditioning to take place. In two experiments, human participants had to learn to collect rewards (monetary gains) while avoiding punishments (monetary losses), on the basis of subliminal outcome-predicting cues. We found that instrumental conditioning can proceed subconsciously only if spatial attention is aligned with the subliminal cue. Conversely, if spatial attention is briefly diverted from the subliminal cue, then instrumental conditioning is blocked. In humans, attention but not awareness is therefore mandatory for instrumental conditioning, thus revealing a dissociation between awareness and attention in the control of motivated behavior.

Monetary reward modulates task-irrelevant perceptual learning for invisible stimuli.

Task Irrelevant Perceptual Learning (TIPL) shows that the brain’s discriminative capacity can improve also for invisible and unattended visual stimuli. It has been hypothesized that this form of “unconscious” neural plasticity is mediated by an endogenous reward mechanism triggered by the correct task performance. Although this result has challenged the mandatory role of attention in perceptual learning, no direct evidence exists of the hypothesized link between target recognition, reward and TIPL. Here, we manipulated the reward value associated with a target to demonstrate the involvement of reinforcement mechanisms in sensory plasticity for invisible inputs. Participants were trained in a central task associated with either high or low monetary incentives, provided only at the end of the experiment, while subliminal stimuli were presented peripherally. Our results showed that high incentive-value targets induced a greater degree of perceptual improvement for the subliminal stimuli, supporting the role of reinforcement mechanisms in TIPL.

The salience of a reward cue can outlast reward devaluation.

Reward cues can be perceived as highly attractive stimuli because of their acquired motivational properties. However, because the motivational value of reward changes after reward receipt, a debated question is whether the attentional salience of reward cues changes accordingly. In Experiment 1, thirsty participants learned 3 cue–reward associations involving different contingencies. Then, while thirsty, participants performed a visual-search task under extinction, during which the previous reward cues appeared as irrelevant stimuli containing target and distractor items. Experiment 2 was identical to Experiment 1, except that participants drank ad libitum before the visual-search task. In Experiment 3, instead, participants quenched their thirst at the beginning of the learning session. The results of Experiment 1 showed that attention was preferentially deployed toward the cue that best predicted the reward in the previous conditioning phase. Crucially, Experiment 2 revealed that the attentional bias persisted despite reward devaluation. By contrast, no attentional bias was found in Experiment 3. The novelty of our study is that the attentional salience of a reward cue can outlast reward devaluation, suggesting that some incentive properties of the cue can become independent from those of the reward.

Perceptual Grouping Enhances Visual Plasticity

Visual perceptual learning, a manifestation of neural plasticity, refers to improvements in performance on a visual task achieved by training. Attention is known to play an important role in perceptual learning, given that the observers discriminative ability improves only for those stimulus feature that are attended. However, the distribution of attention can be severely constrained by perceptual grouping, a process whereby the visual system organizes the initial retinal input into candidate objects. Taken together, these two pieces of evidence suggest the interesting possibility that perceptual grouping might also affect perceptual learning, either directly or via attentional mechanisms. To address this issue, we conducted two experiments. During the training phase, participants attended to the contrast of the task-relevant stimulus (oriented grating), while two similar task-irrelevant stimuli were presented in the adjacent positions. One of the two flanking stimuli was perceptually grouped with the attended stimulus as a consequence of its similar orientation (Experiment 1) or because it was part of the same perceptual object (Experiment 2). A test phase followed the training phase at each location. Compared to the task-irrelevant no-grouping stimulus, orientation discrimination improved at the attended location. Critically, a perceptual learning effect equivalent to the one observed for the attended location also emerged for the task-irrelevant grouping stimulus, indicating that perceptual grouping induced a transfer of learning to the stimulus (or feature) being perceptually grouped with the task-relevant one. Our findings indicate that no voluntary effort to direct attention to the grouping stimulus or feature is necessary to enhance visual plasticity.

Bayesian Confirmation by Uncertain Evidence: A Reply to Huber [2005]

Bayesian epistemology postulates a probabilistic analysis of many sorts of ordinary and scientific reasoning. Huber ([2005]) has provided a novel criticism of Bayesianism, whose core argument involves a challenging issue: confirmation by uncertain evidence. In this paper, we argue that under a properly defined Bayesian account of confirmation by uncertain evidence, Hubers criticism fails. By contrast, our discussion will highlight what we take as some new and appealing features of Bayesian confirmation theory. 1. Introduction2. Uncertain Evidence and Bayesian Confirmation3. Bayesian Confirmation by Uncertain Evidence: Test Cases and Basic Principles Introduction Uncertain Evidence and Bayesian Confirmation Bayesian Confirmation by Uncertain Evidence: Test Cases and Basic Principles

Multiple reward–cue contingencies favor expectancy over uncertainty in shaping the reward–cue attentional salience

Reward-predicting cues attract attention because of their motivational value. A debated question regards the conditions under which the cue’s attentional salience is governed more by reward expectancy rather than by reward uncertainty. To help shedding light on this relevant issue, here, we manipulated expectancy and uncertainty using three levels of reward-cue contingency, so that, for example, a high level of reward expectancy (p = .8) was compared with the highest level of reward uncertainty (p = .5). In Experiment 1, the best reward–cue during conditioning was preferentially attended in a subsequent visual search task. This result was replicated in Experiment 2, in which the cues were matched in terms of response history. In Experiment 3, we implemented a hybrid procedure consisting of two phases: an omission contingency procedure during conditioning, followed by a visual search task as in the previous experiments. Crucially, during both phases, the reward–cues were never task relevant. Results confirmed that, when multiple reward-cue contingencies are explored by a human observer, expectancy is the major factor controlling both the attentional and the oculomotor salience of the reward–cue.