Semantic memory

Question 1

Collins & Quillian (1969) provided evidence that knowledge is stored hierarchically in humans. What was this?

Answer 1

Pps were asked whether a sentence was true or false. RTs were longer when Pps were asked about a feature which required them to ascend the hierarchy by more nodes e.g. slowest first: ‘a canary has skin (superordinate category specific)/ has feathers (basic level category specific)/ can sing (subordinate category specific)’

Question 2

Imagine that aH1 is the activity level of HU1 & aO1 is the activity level of output unit 1, how do we calculate the input from HU1 & net input from all HUs to OU1?

Answer 2

Input from HU1 = aHU1 x hu1-ou1W (the weight of the connection between HU1 & OU1)

Net input from all HUs = E (total of) (aHU x hu-ouW) for each HU

Question 3

When plotting net input against unit activity level, a ___ shaped graph with a ___ gradient around 0 appears. Why?

Answer 3

Sigmoid, sharp. Because the unit is most sensitive to changes in net input around 0 and less sensitive to changes at the extremes of input because min/ max firing rates are reached

Question 4

What logistic function can be used to calculate aOU1 from the net input to OU1?

Answer 4

aOU1 = 1 / (1 + e^-net input to OU1)