Trends in Cognitive Sciences
Volume 17, Issue 9, September 2013, Pages 434-441
Journal home page for Trends in Cognitive Sciences

Opinion
Why skill matters

https://doi.org/10.1016/j.tics.2013.07.001Get rights and content

Highlights

  • Skill makes a behavior quicker and thus increases rewards per unit time.

  • Skill consists of object skill (finding good objects) and action skill (acting on them).

  • Object skill is acquired through repeated experiences of objects with stable values.

  • Object skill allows automatic and quick choices of good objects among many.

  • Object skill compensates for the limited capacity of voluntary search.

Maximizing rewards per unit time is ideal for success and survival in humans and animals. This goal can be approached by speeding up behavior aiming at rewards and this is done most efficiently by acquiring skills. Importantly, reward-directed skills consist of two components: finding a good object (i.e., object skill) and acting on the object (i.e., action skill), which occur sequentially. Recent studies suggest that object skill is based on high-capacity memory for object–value associations. When a learned object is encountered the corresponding memory is quickly expressed as a value-based gaze bias, leading to the automatic acquisition or avoidance of the object. Object skill thus plays a crucial role in increasing rewards per unit time.

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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