Kappa effect: what is this phenomenon of perception?

The Kappa effect is related to our perception of the passage of time and speed.

The Kappa effect is a perceptual illusion, and is further evidence that sometimes our mind and our sensesand is further proof that sometimes our mind and senses deceive us.

In this article we will see what this phenomenon consists of, how it has been studied, to what type of sensory modalities it can be applied and what theories attempt to explain it. As we will see, this perceptual phenomenon is part of a branch of psychology, basic psychology.

What is basic psychology?

The basic psychology is a part of psychology in charge of study a series of psychological and behavioral processes, as well as the laws that govern these processes.. The main areas of research in this branch of psychology are: perception, sensation, learning, reasoning, motivation and memory.

Within the area of perception, we find a series of perceptual illusions, which "deceive" our mind. One of these illusions is the Kappa effect, which is produced before different types of stimuli, and which we will see below.

What is the Kappa effect?

The Kappa effect is a phenomenon of basic psychology; it is also called "perceptual time dilation", and consists of an illusion of perception, which is temporal, and which arises when people observing a series of sensory stimuli occurring sequentially, in different places, judge how much time has elapsed between stimulus and stimulus..

Observers, when perceiving a sequence of stimuli consecutively, tend to overestimate the time elapsed between successive stimuli when the distance between them is sufficiently large; conversely, when the distance is sufficiently small, observers tend to underestimate the time elapsed between stimuli.On the other hand, when the distance is small enough, observers tend to underestimate the time elapsed between stimuli.

Sensory modalities

The Kappa effect can occur with three types of sensory modalities: the visual modality (visual stimuli, such as flashes of light), the auditory modality (e.g. tones) and the tactile modality. (e.g. skin tapping).

1. Visual

Most of the studies developed on the Kappa effect have been conducted with the visual modality, i.e. with visual stimuli. To better illustrate this effect, let us consider the following: three light sources, labeled A, B and C, which are successively illuminated in the dark. The interval between stimulus and stimulus is equal between each of them.

Now imagine that we place these three light sources, A, B and C, in different positions (for example A and B closer together than B and C); if we do so, the observer will perceive that the time interval between the flash of A and B (these sources are closer together), is shorter than the time interval between the flashes of B and C (these sources are farther away from each other).

2. Auditory

In the auditory modality (with auditory stimuli), the Kappa effect has also been demonstrated, although not in all paradigms.although not in all experimental paradigms.

To cite an example, in an experiment conducted by Roy et al. (2011), it was found just the opposite; that when the distance between the different sound sources (auditory stimuli) was increased, the time intervals perceived by the observer, between source and source, were smaller.

In other words, observers perceived a shorter time interval in the presence of increasingly separated stimuli (i.e., they perceived that less time passed between them).

Theories explaining this perceptual illusion

What theories attempt to explain the Kappa effect? Theories that incorporate the element of speed, since this is the element that "links" the is the element that "links" the space between stimulus and stimulus and the temporal interval between them..

Specifically, these theories focus on the expectations of the brain in relation to the speed between stimuli. Let's get to know the three theories that try to explain the Kappa effect, explained in a very summarized way:

1. Low speed expectation

The first theory we are going to explain is the low speed expectation theory. This is based on a model, called Bayesian perceptual model, and tries to explain the Kappa effect in tactile stimuli..

This theory states that brain circuits encode the expectation that tactile stimuli move slowly. This expectation results in our overestimating the time between stimulus onset and stimulus onset.

2. Constant speed expectation

The second theory explaining the Kappa effect basically states that our brain has the expectation that the speed of the stimuli (i.e. the time between stimulus and stimulus) will be constant. This expectation, logically, leads us to make perceptual "errors", and that is why the Kappa effect occurs..

This theory attempted to explain the Kappa effect through a study, which consisted of the following: different participants observed a total of eight white dots in a straight line; these dots appeared successively in a certain direction (horizontal) along the aforementioned straight line.

What happened? That when the temporal interval between stimulus and stimulus (i.e., between their appearance) was constantand their physical separation varied, the Kappa effect was produced (following the hypothesis or theory of constant velocity).

On the other hand, when in the experimental conditions the time interval between stimulus and stimulus was modified, as well as their physical separation, the Kappa effect was not observed (the constant velocity hypothesis was not fulfilled).

What explanation did the researchers offer for this? Basically, it is not easy to perceive uniform motion when the patterns are so diverse and complicated. In this way, they determined how the context of presentation of the stimuli could affect the temporal perception of the observers (i.e., the time we perceive to elapse between stimuli).

Movement in different contexts

The third theory that attempts to explain the Kappa effect is the theory of motion in different contexts. According to this theory the greater the speed of the stimuli, the greater the resulting Kappa effect.e.

This theory also holds that observers have the tendency to apply their previous knowledge regarding movement to a given sequence of stimuli; thus, in different studies, it was observed how, when participants observed vertically positioned stimuli, the Kappa effect was greater in the sequences that moved downward.

How can this be explained? The researchers proposed that we have the prior expectation that acceleration is downward, and that deceleration is upward; following from this, it follows that we underestimate the temporal interval between stimuli (i.e., that we believe they go faster than they actually do).

Bibliographical references:

• Goldstein, E.B. (2006). Sensation and perception. 6th edition. Debate. Madrid.
• Henry, M.J. & McAuley, J.D. (2009). "Evaluation of an imputed pitch velocity model of the auditory kappa effect". Journal of experimental psychology: human perception and performance . 35 (2): 551-64.
• Masuda, T., Kimura, A., Dan, I. & Wada, Y. (2011). Effects of environmental context on temporal perceptual bias in apparent motion " Vision Research 51, 1728-1740.
• Roy, M., Kuroda, T. & Grondin, S. (2011). Effect of space on temporal auditory processing with a single-stimulus method. Advances in sound localization, 95-104.