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Short answer The phenomenon you describe can be explained by the negative afterimage effect, which indeed is elicited by adaptive processes in the retinae. Background In the retina there are three types of color photoreceptors, called cones. They are sensitive to red, green and blue, respectively. Colors are processed in the retina through a process ...


33

Short answer Yes, the flickering of a light bulb may be noticeable, and yes, that's directly related to the mains frequency. However, since the flickering of a bulb is about two times higher than the temporal limits of our visual system, it is unlikely to be perceivable. Background The temporal resolution of the visual system can be quantified in a ...


30

The feeling of cold from mints is caused by menthol. Menthol affects the TRPM8 receptor on skin and also in the mouth. TRPM8 is also a general cold receptor: so if you are in contact with menthol the receptor reacts just like when you are exposed to cold (Bautista et al., 2007). The receptor is strongly activated at temperatures below 26 degrees Celsius (...


27

This is not really a biological answer, but a psychological one: One important fact to consider is that the perception of time is essentially a recollection of past experience, rather than perception of the present. Researchers who study autobiographical memory have suggested that part of this effect may be explained by the number of recallable memories ...


20

TL;DR: We have a good physiological understanding of how eyes work, so by examination of other species' eyes, we can tell a lot about what colours they are capable of seeing. First, a little bit about the physics of colour Light is made of photons, and each photon has a wavelength. The distribution of wavelengths coming from sunlight looks like this (...


15

The basis of this question is a common misconception, and unfortunately the accepted answer by @CHM is also based on this common misconception. The misconception is based on the homunculus falacy: the tendency for people to think that the image that lands on the retina is somehow 'assembled' and presented for something (the 'consciousness') to view. This is ...


14

One important point that you might not be considering is the heat of vaporization. You may be aware that while it normally takes 4.18 J (1 calorie) of heat to raise 1 gram of water 1 °C, it takes around 2250 J of heat to raise 1 g of water from liquid at 99.5 °C to gas at 100.5 °C, due to the energy needed to go from a liquid to a gas. - What you may not ...


13

It's less a problem of speed and more of raw photon count. Assuming a brightly lit day, the bullet will move so fast that it doesn't reflect enough photons to register against the background. High speed images of bullets usually involve a very bright flash (and other controlled settings) for the camera to pick it up. (Also, a very short flash helps the ...


12

Flicker Fusion Threshold: The wikipedia definition: It is defined as the frequency at which an intermittent light stimulus appears to be completely steady to the average human observer. Background In 1824, Peter Mark Roget (who also wrote the famous Thesaurus) first presented the concept of "persistence of vision" to the Royal Society of London, as the ...


12

First recall that pink is white minus green, more or less. Now, your perception can be explained by adaptation: Neurons try to control their gain (amplification factor) to have roughly the same range of output. So if there's a lot of stimuli they like, they will reduce their gain, and vice versa. It can be thought of as a form of fast time-scale homeostasis ...


12

Short answer The effect you describe is called a negative after image. It can be explained by adaptation effects of the photoreceptors in the eye. Background source: Dresden University Steadily fixate on the black lightbulb for thirty seconds or more and then immediately turn your gaze to the white region on the right. The illusionary glowing white bulb ...


10

First of all one should tell that one can attribute the activation of certain brain zones with some indepent events only when the activation takes place along the signal input (receptors, sensory pathways towards the cortex and the sensory areas in cortex) or motor action (=output) (along the motox cortex => motor neuron => target organ). Those zones in ...


10

Short answer The detection threshold of static indentation stimuli on the palm of the hand is approximately 10 to 40 micrometers, dependent on the exact location under investigation. Background The sensitivity of a sensory system can be expressed as the detection threshold. This threshold is in psychophysics generally defined as that stimulus level where, ...


10

Dogs are a dichromatic species, featuring only a long wavelength (L) and a short wavelength (S) cone (source: Smithsonian). As such, they are thought to perceive mainly blues and yellowish hues (Fig. 1). This is unlike trichromatic species like humans, who are able to distinguish red and greens as well (Fig. 2). Whether dogs perceive greens or yellows is ...


9

I can't give a definite answer, and there's nothing in the literature about this specifically, but perhaps some relevant information and a suggested behavioural experiment will help. Background Firstly, I assume you are talking about sodium hypochlorite (which is usually what people mean by bleach)? If so, there are several compounds your cat could be ...


9

There may be some clues in neurobiology. A possibility may be that a person's general emotional state may affect their perception of the passage of time, as argued in this article and references within. Studies of people with damage to their orbitofrontal cortex (prefrontal cortex region) can experience sustained altered emotional states when compared to ...


9

Short answer Yes, we can see with our ears. Background Bach-y-Rita famously stated "We see with our brains, not our eyes". Bach-y-Rita worked for decades on sensory substitution. Sensory substitution approaches in general aim to replace for a lost sense by redirecting information normally captured by that sense to another still functional one. Bach-y-Rita ...


8

There are numerous examples of visual attraction in animals. An absolute classic of an experiment, taught to most/all evolutionary biology students, is the widowbird tail length experiment by Andersson. He experimentally manipulated the tail lengths of male widowbirds at random. Some tails were made longer and some shorter. From this experiment Andersson ...


8

A lamp flickers at 2x the mains frequency, i.e. 100 or 120 Hz, and that is typically not noticeable to human eyes. It is visible to chicken and insects. That being said, a low quality lamp or a lamp at end-of-life may also flicker at 50 or 60 Hz, and you will notice. It depends on the brightness, so an area illuminated by the lamp may not seem to flicker. ...


7

There are strong connections between the auditory cortex and the limbic system, which includes such structures as the hippocampus and the amygdala. A recent paper [1] builds on earlier notions of emotional "significance" of music without any lyrics. It adds in lyrics, so giving a perspective of which portions of the brain are reacting to which component of ...


7

Perception of time can change drastically during an emergency. When we are younger, much like during an emergency, the brain hasn't activated very many filters for sensory data. The young have much to learn about the world and more detail is needed for the brain to make appropriate decisions. Sensory information is recorded in great detail, making time ...


7

Earwax, also called cerumen, is slightly acidic (1), with a pH of about 6, and acidic foods or substances taste sour. The composition of earwax, upon which its taste depends, is related to its functions. Earwax aids in cleaning and lubrication of the ear canal and has an antimicrobial effect. The antimicrobial effect is in part attributed to its acidity, ...


7

To explain the neurophysiological background to the existing answers I would like to add the following: The effect you are describing (pinkish appearance of white) is generally referred to as a negative after image and it is a direct reflection of the color opponency in the retina. The effect is caused by adaptation of the (in this case green) cones in the ...


7

This phenomena has nothing to do with any different kinds of receptors. When we are wet, we have lots of water on our surface. The evaporation of water causes cooling. Blowing wind tends to make evaporation faster. So, even if wind blows at normal temperature, we feel cold. If we are not wet, there is some water on our body surface. This water is low in ...


7

Short answer Cones mediate the perception of white in photopic conditions. Rods mediate the perception of white in scotopic conditions. The rod system is not needed for cones to mediate white perception and vice versa. Background Cones code for red, green and blue. The remaining colors, as you rightfully state in the question, can be generated by mixing ...


6

Maybe the passage of time is perceived as a function of heart rate. Waiting 5 minutes for a turn on the swings is 300 seconds for a 2 year old and 300 seconds for a 40 year old. But that same wait is 575 heart beats for the kid, but only 300 heart beats for the adult.


6

One way we can get evidence qualia are the same or very similar for different people is by reactions to it, beyond just the word. For example, beyond the word "pain", we have other strong reactions to pain. So nobody suspects other people might experience pain as pleasure and vice versa. Obviously not! There are no obvious signs for colour qualia, so it ...


6

Yes, color and shading can certainly affect depth perception, as explained by wikipedia: Aerial perspective – Due to light scattering by the atmosphere, objects that are a great distance away have lower luminance contrast and lower color saturation. Due to this, images seem blurry the farther they are away from a person's point of view. In computer ...


6

Short answer Humans sense temperature differences. Background (Including edits based upon comments) Because the question is "Do humans perceive temperature or heat-flux?", I will answer the answer from a psychophysical perspective, i.e., by dealing with sensory awareness. Just as with many other sensory systems, temperature sensors in the human body ...


6

Short answer Temperature differences of 0.02 degrees Celcius can be distinguished, dependent on various factors including experimental conditions and bodily location. Background The ability to discriminate temperature differences depends on whether it is a cooling or heating pulse, the skin temperature, the duration of the temperature stimulus, age, bodily ...


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