Implicitly learning when to be ready: From instances to categories

There is growing appreciation for the role of long-term memory in guiding temporal preparation in speeded reaction time tasks. In experiments with variable foreperiods between a warning stimulus (S1) and a target stimulus (S2), preparation is affected by foreperiod distributions experienced in the past, long after the distribution has changed. These effects from memory can shape preparation largely implicitly, outside of participants’ awareness. Recent studies have demonstrated the associative nature of memory-guided preparation. When distinct S1s predict different foreperiods, they can trigger differential preparation accordingly. Here, we propose that memory-guided preparation allows for another key feature of learning: the ability to generalize across acquired associations and apply them to novel situations. Participants completed a variable foreperiod task where S1 was a unique image of either a face or a scene on each trial. Images of either category were paired with different distributions with predominantly shorter versus predominantly longer foreperiods. Participants displayed differential preparation to never-before seen images of either category, without being aware of the predictive nature of these categories. They continued doing so in a subsequent Transfer phase, after they had been informed that these contingencies no longer held. A novel rolling regression analysis revealed at a fine timescale how category-guided preparation gradually developed throughout the task, and that explicit information about these contingencies only briefly disrupted memory-guided preparation. These results offer new insights into temporal preparation as the product of a largely implicit process governed by associative learning from past experiences.

Head-Restrained Lever Go/NoGo Visual Discrimination Task with Visiomode v2

This protocol is an adaptation of Michelle's lever Go/NoGo auditory discrimination task, which uses visual instead of auditory stimuli. Water-restricted, headplated mice learn to discriminate between a target and a distractor stimulus presented serially in pseudo-random order, pushing a lever to indicate when the target stimulus appears. The protocol is designed for across-learning recordings, and as such the inter-trial interval and stimulus interval remain constant throughout. Correction trials are also enabled throughout the duration of the protocol. The task in implemented in the Visiomode platform, using the lever apparatus for response input instead of the touchscreen. This protocol uses the Citric Acid Water Restriction protocol with sucrose rewards, instead of the traditional water deprivation protocol.

Assessing the inhibitory properties of a latent inhibitor in flavor-aversion learning

In Experiment 1, rats received 16 nonreinforced trials of exposure to a flavor (A) that was subsequently used as the conditioned stimulus in flavor-aversion conditioning. In the critical condition, Flavor A was presented in compound with a different novel flavor on each of the eight daily trials. This treatment produced latent inhibition, in that this preexposure retarded conditioning just as did 16 trials with A alone. Rats in the control conditions, given no preexposure or exposure just to the sequence of novel flavors, learned readily. Experiment 2 examined the effects of these forms of preexposure on performance on a summation test, in which Flavor A was presented in compound with a separately conditioned flavor (X). The preexposure procedure in which A was presented along with novel flavors rendered A effective in inhibiting the response conditioned to X on that test. The conclusion, that this form of training can establish the target stimulus as a conditioned inhibitor, is predicted by the account of latent inhibition put forward by Hall and Rodríguez (2010) which proposes that the latent inhibition effect is a consequence both of a reduction in the associability of the stimulus and of a process of inhibitory associative learning that opposes the initial expectation that a novel event will be followed by some consequence.

EXPRESS: The vertical space-time association

The space-time interaction suggests a left-to-right directionality in the mind’s representation of elapsing time. However, studies showing a possible vertical time representation are scarce and contradictory. In Experiment 1, 32 participants had to judge the duration (200, 300, 500 or 600 milliseconds) of the target stimulus that appeared at the top, centre, or bottom of the screen, compared to a reference stimulus (400 milliseconds) always appeared in the centre of the screen. In Experiment 2, 32 participants were administered with the same procedure, but the reference stimulus appeared at the top, centre, or bottom of the screen and the target stimulus was fixed in the centre location. In both experiments, a space-time interaction was found with an association between short durations and bottom response key as well as between long durations and top key. The evidence of a vertical mental timeline was further confirmed by the distance effect with a lower level of performance for durations close to that of the reference stimulus. The results suggest a bottom-to-top mapping of time representation, more in line with the metaphor “more is up”.

Attention to a Moment in Time Impairs Episodic Distinctiveness during Rapid Serial Visual Presentation

Human attention is limited in the ability to select and segregate relevant distinct events from the continuous flow of external information while concurrently encoding their temporal succession. While it is well-known that orienting attention to one external target stimulus impairs the encoding of ensuing relevant external events, it is still unknown whether orienting attention to internally generated events can interfere with concurrent processing of external input. We addressed this issue by asking participants to identify a single target embedded among distractors in a non-spatial rapid serial visual presentation (RSVP) stream and to indicate whether that target appeared before or after an internally estimated midpoint of the stream. The results indicate that (a) such an internally generated temporal benchmark does not interfere with the identification of a subsequent physical target stimulus but (b) the two events cannot be accurately segregated when the physical target immediately follows the internally generated temporal event. These findings indicate that the asymmetrical distribution around the midpoint of order reversals reflects an impaired temporal discrimination ability. Orienting attention to a moment in time reduces episodic distinctiveness as much as orienting attention to external events.

A few remarks on "uncrowding" in visual stimuli

Visual crowding occurs when a target stimulus is presented along with flanking stimuli. These tend to reduce the visibility of the target. It has been found that adding additional flanking stimuli may reduce the crowding effect. This has been termed "uncrowding". It has previously been demonstrated that interference in the stimuli may have effects similar to visual crowding. Interference takes place in the stimuli and is unrelated to vision. The question is then: Can adding additional flanking stimuli reduce the interference effect of initial flanking stimuli in a manner consistent with uncrowding. The present simple calculations indicate that this is very much a possibility.

Unmasking the Effects of Orthography, Semantics, and Phonology on 2AFC Visual Word Perceptual Identification

In the two-alternative forced-choice (2AFC) task, the target stimulus is presented very briefly, and the participants must choose between two options as to which was the presented target. Some past research (Grossi et al., 2009; Haro et al., 2019) has assumed that the 2AFC word identification task isolates orthographic effects, despite orthographic, semantic, and phonological differences between the alternative options. If so, performance should not differ between word target/nonword foil pairs and British/American word pairs, the latter of which only differ orthographically. In Experiment 1, accuracy and sensitivity were higher during word/nonword trials than British/American trials when participants stated their response was not a guess, demonstrating that phonological/semantic processing contributes to 2AFC performance. In Experiment 2, target visibility was manipulated by increasing the contrast between target and mask for half the trials. Experiment 2 showed that target visibility did not interact with pair type on reaction time, which suggests phonological/semantic processing did not result in feedback to orthographic encoding in this task. This study demonstrates the influence of phonological/semantic processing on word perceptual identification, and shows that 2AFC word identification does not isolate orthographic effects when word/nonword pairs are used, but using British/American word pairs provides a method for doing so. Implications for models and future research are discussed.

On interference between target and noise in visual stimuli

Visual stimuli in which a target is presented on a background of noise have been used widely in visionresearch. Adding a background of noise tends to reduce performance. Such reductions have typically beenattributed to factors in the visual system. The present analyses demonstrates how there may be interferencebetween target and noise. This interference takes place in the stimuli rather than in the visual system. Ittakes place even if the stimuli are not being seen. The interference causes the amplitudes in the combinedtarget and noise stimulus to be smaller than the amplitudes in the target plus the amplitudes in the noisewhen these are determined separately. Therefore, the full amplitudes of the target and those of the noisecannot all be contained in the amplitudes of the combined stimulus. As a consequence one cannot counton a target stimulus to have the same stimulus power when presented on a background of noise as whenpresented on a uniform background.

Is Face Age Mapped Asymmetrically onto Space? Insights from a SNARC-like Task

The magnitude associated with a stimulus can be spatially connoted, with relatively smaller and larger magnitudes that would be represented on the left and on the right side of space, respectively. According to recent evidence, this space–magnitude association could reflect specific brain asymmetries. In this study, we explored whether such an association can also emerge for face age, assuming that responders should represent relatively younger and older adult faces on the left and on the right, respectively. A sample of young adults performed a speeded binary classification task aimed at categorising the age of a centrally placed adult face stimulus as either younger or older than the age of a reference face. A left-side and a right-side response key were used to collect manual responses. Overall, older faces were categorised faster than younger faces, and response latencies decreased with the absolute difference between the age of the target stimulus and the age of the reference, in line with a distance effect. However, no evidence of a left-to-right spatial representation of face age emerged. Taken together, these results suggest that face age is mapped onto space differently from other magnitudes.

Background stimulus delays detection of target stimulus in a familiar odor–odor combination

Familiarity of odor–odor combinations is enhanced through food intake in daily life. As familiarity increases, the perceptual boundary between two odors may become ambiguous; therefore, we hypothesized that exposure to one odor would delay detection of the other in a high-familiarity combination but not in a low-familiarity combination. To test this hypothesis, we measured the speed of odor detection using two types of background stimuli (black tea odor and odorless air) and two types of target stimuli (lemon odor and almond odor). For Japanese participants, the combination of black tea and lemon odor has high familiarity, whereas the combination of black tea and almond odors has low familiarity. Reaction time for detection of target stimulus was measured by inserting a pulsed target stimulus into the flow of the background stimulus (i.e., replacing the background stimulus with the target stimulus for a short time). Reaction time for detection of lemon odor was significantly longer under the black tea odor condition than under the odorless air condition. Reaction time for detection of almond odor was similar between the black tea odor and odorless air conditions. These results are in line with the hypothesis that familiarity of an odor–odor combination affects odor detection speed. Further investigations are required to reach more robust conclusions.