SENSE PERCEPTION WHAT CAN OUR SENSES PERCEIVE?

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SENSE PERCEPTION OVERVIEW Constant external objects? –Brain in the Vat –Descartes –Ockham's Razor Limitations of our senses –What we can (and cannot!) perceive –Tricks played by our senses: illusions "Innocent eye?“ TOK Implications!

WHAT OUR SENSES CAN PERCEIVE... If the stimuli are strong enough.

© SIGHT: 1 % of the electromagnetic spectrum. (We sense radio waves as sound, infrared as heat, ultraviolet, X-rays, and gamma rays as damage to our cells.)

© SOUND: Frequencies between 16 and 20,000 Hz.

© TOUCH: Regions of our body differ in sensitivity. Two points are perceived as distinct at a distance of­ 1 mm on our tongues 70 mm on our backs.

© SMELL: A slight sweetness is better perceived using the tip of the tongue.

OCKHAM'S (OCCAM'S) RAZOR a.k.a. Law of Parsimony or Law of Economy –William of Ockham ( ): "Non sunt multiplicanda entia prater necessitatem." (Entities are not to be multiplied beyond necessity.) –Ernest Mach ( ): "It is the aim of science to present the facts of nature in the simplest and most economical conceptual formulations."

"INNOCENT EYE?" Perception influenced (at the very least) by: –Attention (we cannot process everything that reaches our senses) –Convention & cultural aspects (e.g. right angles, perspective) –Belief / Language (to what extent do we perceive what is incongruent to our past experiences?) –Expectations (familiar sights, ET's) To organize sense perceptions in our brains, we require, at the very least, the following learned factors: –Context Inference Concepts Experience Interpretation

What's wrong with this figure?

The is a physical model of an impossible staircase designed by genetist Lionel Penrose. It is the first impossible object ever made and served as an inspiration for M. C. Escher's famous print that incorporates this staircase, "Ascending and Descending." The actual model is separated at the right stair, but you can't see the split, because your visual system assumes that it is seeing this model from a non-accidental point of view; hence, it assumes that the stairs are joined.M. C. Escher's"Ascending and Descending." Although the staircase is conceptually impossible, it does not interfere with your perception of it. In fact, the paradox is not even apparent to many people. So what's Happening?