Trends in Cognitive Sciences
OpinionWhy skill matters
Section snippets
The evolutionary advantages of skill
The majority of daily human activities, such as lacing shoes, writing with a pencil, riding a bicycle, or using a computer, involve skilled behavior that is carried out with little or no conscious thought. Each kind of skill may be acquired through prolonged and intensive practice across many years 1, 2. This is not unique to modern human societies. In less-labor-divided societies (e.g., hunter–gatherer societies) hunting is a dominant skill among men. The hunting skill is learned gradually
An earlier reward is more valued
Given the following option: ‘you can take US$10 now but if you wait until the next week you will receive US$15’, many people would choose the former even though there is a smaller outcome. This phenomenon is common to humans and animals 14, 15 and is often referred to as ‘temporal discounting of rewards’. Why is an early reward more valued than a late reward? A standard answer in economics is that the value of a future reward is discounted because of the risk involved in waiting for it [16]. An
Motivation and skill reduce the duration of behavior
The speed of behavior (and consequently its value) can be increased temporarily by motivation or permanently by skill (Figure 2A). Motivation is initiated quickly if a reward is expected but is dissolved quickly if no reward is expected. Its major advantage is flexibility. Skill is acquired slowly by repeating a behavior but is maintained for a long time. Its major advantage is stability. Which one is more effective in reducing reward delay? The duration of a behavior (e.g., saccadic eye
Two kinds of skill
Our main message above was: reward delay can be shortened by accelerating one's own behavior. But what exactly does ‘behavior’ mean? Human hunters as well as monkeys spend time in capturing an animal as their food resource 3, 29. But, before that, they need to find the animal using various sensory cues. By repeated experience, the humans and monkeys become proficient in finding good prey animals and capturing them. Thus, the modifiable reward delay consists of two components: (i) the delay
Object skill – stable values
In attention and perceptual learning experiments the subjects are usually presented with stimuli or objects and are asked to choose one of them. In everyday life, however, there is often no such instruction. We choose a particular object because, by doing so, we accomplish something rewarding, probably multiple times. We avoid an object because the outcome was less rewarding or punishing. In other words, the proficiency of finding good objects is the result of value-based learning 41, 42.
Object skill – gaze and attention
There are several ways of finding a good object. Animals may use different sensory modalities – visual, auditory, somatosensory, olfactory, electromagnetic, etc. 47, 48, 49. For primates including humans, visual information is a dominant modality 50, 51. Indeed, studies on humans and monkeys have suggested that gaze and/or attention is drawn to an object that has a high value 52, 53, 54, 55, 56, 57, 58, which is often followed by a manual action performed on the object 59, 60, 61, 62. The
Object skill – automaticity
Skills are characterized by automaticity 2, 7, 69. When human observers have extensively learned to find particular visual objects they become unaware of their own perceptual distinction or memory retrieval 32, 33, 70. The automatic nature of object skill is important. Suppose you have experienced all of the fractals in Figure 3, half of them with a reward and the other half with no reward, many times. Suppose, then, some of these objects are placed in front of you (Figure 4B). Can you choose
Object skill – high-capacity memory
It is now clear that object skill requires high-capacity memory. The association of an object and its stable value makes up a single memory. The number of memories should correspond to the number of learned objects. This is the minimum requirement, however. If a combination of objects has a different value (which is likely) the number of memories would increase drastically. Moreover, the object–value memory must have a robust access to motor outputs, so that we can physically choose high-valued
Object skill – long-term retention
Human studies on the value-based gaze/attention bias have shown that, once the subjects have acquired a bias, the bias is retained for several days 57, 80. Studies using monkeys showed that the value-based gaze bias remains robust for more than 100 days [65]. In this specific study [65], the monkeys were not shown some of the value-associated objects for a long time and then their choices were suddenly tested using free viewing. The monkeys looked at the previously high-valued objects
Object skill – limitations
So far, we have emphasized the advantage of skill, especially object skill. However, relying on object skill completely is risky because of its automatic nature. Object skill is basically blind to recent changes in the values of individual objects. If a previously high-valued object becomes toxic we may not be able to stop reaching for it [53]. This poses a serious problem because motor behavior triggered by object skill (e.g., gaze orienting and reaching) occurs quickly and automatically in
Concluding remarks
An ultimate advantage of skilled behavior is multitasking [91]. Because skills are automatic, more than one can be performed in parallel (including a combination of object and action skills). Object skill enables humans and animals to evaluate objects in every environment and choose a high-valued object quickly and automatically. The choice then enables humans and animals to act on the chosen object quickly so that rewarding outcome can be presented as soon as possible. When one is writing a
Acknowledgments
This work was supported by the intramural research program at the National Eye Institute.
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