The color "fruit": object memories defined by color

Visual mental imagery of atypical color objects attracts attention to an imagery-matching object

Mental imagery attracts attention to imagery-matching stimuli. However, it remains unknown whether voluntarily imagined atypical color also attracts attention to a stimulus that matches the imagery when the imagined stimuli are color-diagnostic objects, which are strongly associated with typical color. This study investigated whether people can voluntarily imagine atypical colors of such objects and attend to imagery-matching stimuli. Participants in the imagery group were instructed to imagine an atypical color of the black-white objects according to the instructed color or voluntarily selected color, whereas participants in the control group were instructed to attend to the objects without any instruction of imagery. Thereafter, they detected a color target in a visual search task. Results revealed that participants in the imagery group directed attention to the imagery-matching atypical color, not to the original color of the object in the search. Meanwhile, participants in the control group did not demonstrate any attentional guidance. These results suggest that voluntarily imagining atypical color can attenuate mental representations of the original color imagery and change attention to a stimulus that matches imagery.

The phase of Theta oscillations modulates successful memory formation at encoding

Several studies have shown that attention and perception can depend upon the phase of ongoing neural oscillations at stimulus onset. Here, we extend this idea to the memory domain. We tested the hypothesis that ongoing fluctuations in neural activity impact memory encoding in two experiments using a picture paired-associates task in order to gauge episodic memory performance. Experiment 1 was behavioural only and capitalized on the principle of phase resetting. We tested if subsequent memory performance fluctuates rhythmically, time-locked to a resetting cue presented before the to-be-remembered pairs at different time intervals. We found an indication that behavioural performance was periodically and selectively modulated at Theta frequency (~4 Hz). In Experiment 2, we focused on pre-stimulus ongoing activity using scalp EEG while participants performed a paired-associates task. The pre-registered analysis, using large electrode clusters and generic Theta and Alpha spectral ranges, returned null results of the pre-stimulus phase-behaviour correlation. However, as expected from prior literature, we found that variations in stimulus-related Theta-power predicted subsequent memory performance. Therefore, we used this post-stimulus effect in Theta power to guide a post-hoc pre-stimulus phase analysis in terms of scalp and frequency of interest. This analysis returned a correlation between the pre-stimulus Theta phase and subsequent memory. Altogether, these results suggest that pre-stimulus Theta activity at encoding may impact later memory performance.

Object knowledge changes visual appearance: semantic effects on color afterimages

According to predictive coding models of perception, what we see is determined jointly by the current input and the priors established by previous experience, expectations, and other contextual factors. The same input can thus be perceived differently depending on the priors that are brought to bear during viewing. Here, I show that expected (diagnostic) colors are perceived more vividly than arbitrary or unexpected colors, particularly when color input is unreliable. Participants were tested on a version of the 'Spanish Castle Illusion' in which viewing a hue-inverted image renders a subsequently shown achromatic version of the image in vivid color. Adapting to objects with intrinsic colors (e.g., a pumpkin) led to stronger afterimages than adapting to arbitrarily colored objects (e.g., a pumpkin-colored car). Considerably stronger afterimages were also produced by scenes containing intrinsically colored elements (grass, sky) compared to scenes with arbitrarily colored objects (books). The differences between images with diagnostic and arbitrary colors disappeared when the association between the image and color priors was weakened by, e.g., presenting the image upside-down, consistent with the prediction that color appearance is being modulated by color knowledge. Visual inputs that conflict with prior knowledge appear to be phenomenologically discounted, but this discounting is moderated by input certainty, as shown by the final study which uses conventional images rather than afterimages. As input certainty is increased, unexpected colors can become easier to detect than expected ones, a result consistent with predictive-coding models.

Searching for flavor labels in food products: the influence of color-flavor congruence and association strength

Prior research provides robust support for the existence of a number of associations between colors and flavors. In the present study, we examined whether congruent (vs. incongruent) combinations of product packaging colors and flavor labels would facilitate visual search for products labeled with specific flavors. The two experiments reported here document a Stroop-like effect between flavor words and packaging colors. The participants were able to search for packaging flavor labels more rapidly when the color of the packaging was congruent with the flavor label (e.g., red/tomato) than when it was incongruent (e.g., yellow/tomato). In addition, when the packaging color was incongruent, those flavor labels that were more strongly associated with a specific color yielded slower reaction times and more errors (Stroop interference) than those that were less strongly tied to a specific color. Importantly, search efficiency was affected both by color/flavor congruence and association strength. Taken together, these results therefore highlight the role of color congruence and color–word association strength when it comes to searching for specific flavor labels.

Progesterone and mental imagery interactively predict emotional memories

Different lines of research suggest that the consolidation of emotional memories is influenced by (a) endogenous levels of sex hormones, and (b) individual differences in the capacity to use vivid mental imagery. No studies to date have investigated how these factors may interact to influence declarative emotional memories. This study examined the interacting influence of progesterone and mental imagery strength on emotional memory consolidation. Twenty-four men, 20 women from the low progesterone (follicular) menstrual phase, and 20 women from the high progesterone (mid-luteal) phase of the cycle were assessed using an objective performance-based measure of mental imagery strength, and then shown a series of aversive and neutral images. Half of the images were accompanied by instructions to process sensory features, and the remaining half to process the conceptual characteristics of the images. Two days later, all participants returned for a surprise free recall memory test. The interaction of progesterone and mental imagery strength significantly predicted recall of visually processed, but not verbally processed, negative images. These data suggest that mental imagery strength may be one mechanism underlying the documented association between endogenous progesterone and enhanced emotional memory performance in the literature.

Unconscious local motion alters global image speed

Accurate motion perception of self and object speed is crucial for successful interaction in the world. The context in which we make such speed judgments has a profound effect on their accuracy. Misperceptions of motion speed caused by the context can have drastic consequences in real world situations, but they also reveal much about the underlying mechanisms of motion perception. Here we show that motion signals suppressed from awareness can warp simultaneous conscious speed perception. In Experiment 1, we measured global speed discrimination thresholds using an annulus of 8 local Gabor elements. We show that physically removing local elements from the array attenuated global speed discrimination. However, removing awareness of the local elements only had a small effect on speed discrimination. That is, unconscious local motion elements contributed to global conscious speed perception. In Experiment 2 we measured the global speed of the moving Gabor patterns, when half the elements moved at different speeds. We show that global speed averaging occurred regardless of whether local elements were removed from awareness, such that the speed of invisible elements continued to be averaged together with the visible elements to determine the global speed. These data suggest that contextual motion signals outside of awareness can both boost and affect our experience of motion speed, and suggest that such pooling of motion signals occurs before the conscious extraction of the surround motion speed.